UNITED STATES OF AMERICA
FOOD AND DRUG ADMINISTRATION
CENTER FOR BIOLOGICS EVALUATION AND RESEARCH
+ + + + +
TRANSMISSIBLE SPONGIFORM ENCEPHALOPATHIES ADVISORY
FEBRUARY 12, 2004
This transcript has not been edited
Or corrected, but appears as received
From the commerical transcribing
Service. Accordingly, the Food and
Drug Administration makes no
Representation as to its accuracy.
The Advisory Committee met at 8:00 a.m. in the Kennedy Ballroom of the Holiday Inn Silver Spring, 8777 Georgia Avenue, Silver Spring, Maryland, Dr. Suzette A. Priola, Chairperson, presiding.
SUZETTE A. PRIOLA, Ph.D. Chairperson
JOHN C. BAILAR III, M.D., Ph.D. Member
VAL D. BIAS Member
ARTHUR W. BRACEY, M.D. Member
LYNN H. CREEKMORE, D.V.M. Member
STEPHEN J. DeARMOND, M.D., Ph.D. Member
LISA FERGUSON, D.V.M. Consultant
PIERLUIGI GAMBETTI, M.D. Member
R. NICK HOGAN, M.D., Ph.D. Member
ALLEN JENNY, D.V.M. Consultant
RICHARD T. JOHNSON, M.D. Member
RIMA KHABBAZ, M.D. Consultant
JEANNE LINDEN, M.D., M.P.H. Consultant
KENRAD NELSON, M.D. Consultant
GEORGE NEMO, Ph.D. Consultant
STEPHEN R. PETTEWAY, JR., Ph.D. Non-Voting
JAMES SEJVAR, M.D. Consultant
SIDNEY WOLFE, M.D. Consultant
WILLIAM FREAS, Ph.D. Executive Secretary
PAUL BROWN, M.D., NIH - Laboratory of Central Nervous
JOSHUA COHEN, Ph.D., Harvard Center for Risk Analysis
LISA FERGUSON, D.V.M., USDA - APHIS
ALLEN JENNY, D.V.M., National Veterinary Service
MARY PORRETTA, USDA - FSIS
ROBERT ROHWER, Ph.D., VA Medical Center - Baltimore
JAMES SEJVAR, M.D., Centers for Disease Control and
ROBERT G. WILL, M.D., National CJD Surveillance Unit,
STEVEN ANDERSON, Ph.D. CBER
DAVID M. ASHER, M.D. CBER
JAY EPSTEIN, M.D. CBER
JESSE GOODMAN, M.D. CBER
STEPHEN SUNDLOF Center for Veterinary Medicine
C O N T E N T S
Introductions .................................. 6
Conflict of Interest Statement ................. 9
Retirement Awards ............................. 12
Dr. Jesse Goodman ....................... 14
Possible Transfusion Transmitted Case of vCJD,
Dr. Robert Will ......................... 20
CJD Surveillance in the United States, Dr.
James Sejvar ............................ 58
Comparison of the Transfusion Risk for CJD v.
vCJD, Dr. Steve Anderson ................ 75
Experimental Studies in Animals Re TSE Infectivity:
Review of Recent Experiments in Rodents and
Sheep, Dr. Robert Rohwer ................ 91
Review of Recent Experiments in Non-human
Primates, Dr. Paul Brown ............... 136
Open Public Hearing
Dr. Michael Fitzpatrick ................ 162
Dr. Hatte Blejer ....................... 165
Review of Reported Case of BSE in Washington State:
Case Presentation and USDA Surveillance Program,
Dr. Lisa Ferguson ...................... 201
Confirmation of BSE in the Affected Cow,
Dr. Al Jenny ........................... 229
Food Safety Regulations for BSE, Mary
Porretta ............................... 236
C O N T E N T S (Continued)
Status of U.S. Feed Ban, Dr. Stephen
Sundlof ................................ 257
FDA Presentation, Dr. David Asher ............ 268
DR. FREAS: Mr. Chairman, members of the committee, invited speakers, and members of the public, I would like to welcome all of you to this, our 15th meeting of the Transmissible Spongiform Encephalopathies Advisory Committee.
The entire meeting, both today and tomorrow, will be open to the public, and you're welcome to attend.
I am Bill Freas. I am the Executive Secretary for this Advisory Committee. At this time I would like to go around the head table and introduce the members seated at the head table to the public. We'll be starting on the public's right-hand side of the room.
When I call your name, if you would raise your hand. The first hand will not be raised, but that seat will soon be occupied by Dr. Richard Johnson, Professor of Neurology, Johns Hopkins University.
Next is Dr. Lisa Ferguson, Senior Staff Veterinarian, U.S. Department of Agriculture.
Next, Dr. Arthur Bracey, Associate Chief, Department of Pathology, St. Luke's Episcopal Hospital.
Next, Dr. Rima Khabbaz, Associate Director for Epidemiologic Science, National Center for Infectious Diseases, Atlanta, Georgia.
Next, Dr. George Nemo, Division of Blood Diseases and Resources, National Institutes of Health.
Next we have an empty chair. Unfortunately Shirley Walker, our Consumer Representative had a medical emergency and she could not be with us this morning.
Next, Dr. John Bailar hopefully will be joining us later. Dr. Bailar is Professor Emeritus, University of Chicago.
Next, Dr. Sidney Wolfe, Director, Public Citizen Health Research Group.
Around the corner of the table, Dr. Nick Hogan, Associate Professor of Ophthalmology, University of Texas Southwestern Medical School.
Next, Dr. Kenrad Nelson, Professor, Department of Epidemiology, Johns Hopkins University School of Hygiene and Public Health. Dr. Nelson is also the Chair of CBER's Blood Products Advisory Committee.
Next is the chair of this committee, the Transmissible Spongiform Encephalopathies Advisory Committee, Dr. Suzette Priola, Investigator, Laboratory of Persistent and Viral Diseases, Rocky Mountain Laboratories.
Next, we have Dr. Allen Jenny from the Pathobiology Laboratory, National Veterinary Services Laboratory, Ames, Iowa.
Around the corner of the table we have Dr. James Sejvar, Neural Epidemiologist, Division of Viral and Rickettsial Diseases, CDC.
Next, we have Dr. Stephen DeArmond, Professor of Pathology, University of California, San Francisco.
Next, we have Mr. Val Bias, Co-Chairman, Blood Safety Working Group, National Hemophilia Foundation.
Next, Dr. Pierluigi Gambetti, Professor and Director, Division of Neural Pathology, Case Western Reserve University.
Next, we have Dr. Lynn Creekmore, Staff Veterinarian, APHIS, USDA.
Next, we have Dr. Jeanne Linden, Director of Blood and Tissue Resources, New York State Department of Health.
Next, we have our non-voting Industry Representative, Dr. Stephen Petteway, Director of Pathogen Safety and Research, Bayer Corporation.
I would like to thank all of our committee members and consultants for joining with us this morning.
Now, I would like to read into the public record the conflict of interest statement that is required for this meeting.
The following announcement is made part of the public record to preclude even the appearance of a conflict of interest at this meeting. Pursuant to the authority granted under the committee charter, the director, Center for Biologics Evaluation and Research, has appointed for this meeting the following participants as temporary voting members. They are Drs. Lisa Ferguson, Allen Jenny, Rima Khabbaz, Jeanne Linden, Kenrad Nelson, George Nemo, James Sejvar, Sidney Wolfe, and Ms. Shirley Walker.
Based on the agenda, it has been determined that the committee will not be providing advice on specific firms or products at this meeting. The topics being discussed by the committee are considered general matters issues.
To determine if any conflicts of interest exist, the agency reviewed the agenda and all relevant financial interests reported by the meeting participants. The Food and Drug Administration prepared general matters waivers for participants who required a waiver under 18 U.S. Code 208. Because the general topics impact on so many entities, it is not prudent to recite all of the potential conflicts of interest as they apply to each member.
FDA acknowledges that there may be potential conflicts of interest, but because of the general nature of the discussion before the committee, these potential conflicts are mitigated.
We would like to note for the record that Dr. Stephen Petteway is a non-voting Industry Representative for this committee acting on behalf of the regulated industry. Dr. Petteway's appointment is not subject to 18 U.S. Code 208. He is employed by Bayer and, thus, has a financial interest in his employer and other similar firms.
In the interest of fairness, FDA is disclosing that Dr. Petteway is also a member of the Viral Safety Working Group at the Plasma Protein Therapeutics Association.
With regards to FDA's invited guest speakers, the agency has determined that the service of these speakers are essential. The following interests are being made public to allow the participants to objectively evaluate any presentation and/or comments made by these speakers.
Dr. Joshua Cohen has a grant from FDA to study BSE, and he is receiving consulting fees from the USDA.
Dr. Robert Rohwer has financial interests with various firms that could be affected by the committee discussions.
Dr. Robert Will is employed by the National CJD Surveillance Unit, Western General Hospital in Edinburgh, U.K. He also consults and advises with firms that could be affected by the committee discussions.
Members and consultants are aware of the need to exclude themselves from discussions involving specific products or firms for which they have not been screened for conflict of interest. Their exclusion will be noted in the public record.
With respect to all other meeting participants, we ask in the interest of fairness that you address any current or previous financial involvement with any firm whose products you wish to comment upon. Waivers are available by written request under the Freedom of Information Act.
So ends the reading of the conflict of interest statement.
Dr. Priola, I turn the meeting over to you.
CHAIRPERSON PRIOLA: Thank you, Bill.
Before we get started, Dr. Jesse Goodman is going to present some retirement awards for retiring members of the committee.
DR. GOODMAN: Okay. We're very happy to present these awards for people who are retiring from the committee, and the first one is Lisa Ferguson, the Senior Staff Veterinarian from the USDA.
So, Lisa, if you'd come up, we thank you for all of your good service. Okay. There's a plaque, which is very nice, and there's a letter.
DR. GOODMAN: There's a letter which will probably be of high value. I didn't sign it, but it's signed by the Associate Commissioner for External Affairs, my colleague Peter Pitts, and it says that he'd like to express his deepest admiration for your efforts. And, of course, all of us appreciate these efforts in behalf of public health and the incredibly useful advice that you give all of us at FDA.
So thank you, Lisa.
DR. GOODMAN: Do you want a picture?
This is actually the first recorded USDA-FDA handshake.
DR. GOODMAN: I probably closed my eyes. You'll have that to remember me by.
Okay. And then my dear colleague from CDC Rima Khabbaz who has been one year on the TSEAC and also serves on our Blood Product Advisory Committee, right?
Okay. So does she get, like, eight plaques?
DR. GOODMAN: No, just one plaque, the same plaque, same letter from Dr. Pitts, but addressed to you. So thank you.
DR. GOODMAN: Thank you.
DR. GOODMAN: Okay. And then we have Dr. Sid Wolfe, who's the Director, as you know, of the Public Citizen Health Research Group. Again, Sid, we tremendously appreciate your input here, and again, all you do on this committee and elsewhere as an advocate for public health. We really appreciate that.
DR. GOODMAN: I have a brief introduction for the Committee and also a little bit of an apology in advance to the members that, as usual, I can't stay for the whole thing, but Karen Midthun over there who is Acting Deputy Director of the Center will be trying to stay for the whole thing. And this is a particularly important Advisory Committee for us because of the concerns that have occurred and our desire to really be on top of this issue.
Anyhow, I'm pleased to welcome the members of the TSE Advisory Committee; in addition, our invited speakers; and also certainly the public who are here today. And we welcome public interest and input.
The purpose of this meeting is to discuss with the Committee current safeguards to minimize the risk of transmission of CJD and variant CJD by FDA medical products. Although we discuss these kinds of issues periodically with this committee, as everybody knows, this discussion is coming at a particularly timely moment. This is really because of two important events that have occurred just within the last couple of months.
First of all, in the United Kingdom, a case of variant CJD was recognized in a blood transfusion recipient who had received packed red cells six and a half years earlier from the donor who later developed variant CJD. Although it's possible, of course, that both the donor and the recipient were infected independently and coincidentally related to their food exposure in the U.K., given a consideration of the odds of these events, FDA considers this observation to at least be presumptive evidence that variant CJD can be transmitted by some components of human blood, again, not proven, but highly suggestive and presumptive when one approaches it in a cautious manner.
The theoretical possibility for such a transmission was recognized for at least 15 years, but this case would represent the first actual evidence for blood-borne transmission in humans. The FDA has actually, since 1987, recommended a series of precautionary steps to reduce the risk of blood-borne CJD even when it was a theoretical risk.
So this recent event may not necessitate any dramatic change in our thinking, but it does draw our attention to this issue and the need for what we have been doing, which is a periodic reevaluation of our blood policies, and the public health protections that we have in place, and also the consideration of whether there are additional steps or thoughts that you may have to help us deal with this issue.
Okay. The second issue is that later in December of this last year, the USDA reported the presence of bovine spongiform encephalopathy that had been diagnosed in postmortem examination of brain of a disabled dairy cow in Washington State, and this was later determined, as folks know, to have originated in Canada. There have been a number of subsequent investigations ? and I think we'll hear a little more about that ? and in these the USDA has not identified to date any other cows with BSE, but certainly this finding, together with the recognition of BSE in a Canadian beef breeder cow earlier last year, again, provide what we consider a significant impetus to continue an ongoing evaluation and consideration of related issues of medical product safety.
So, therefore, we have asked the TSE Advisory Committee in the next two days to discuss possible implications of these two events for the safety of medical products, and that includes devices, drugs, and biologics that are regulated by the FDA. And as members of the Committee know, what we ask the FDA advisory committees to do is to discuss underlying scientific questions that may bear on our regulatory policies to protect public health.
To assist the Committee, the first topic of the meeting will be a review of available information about the presumptive transfusion-transmitted case, related experimental and epidemiological data that are available, and a risk assessment.
The second informational topic will be a review of the recent North American BSE case, as we mentioned, the second indigenous case found on this continent; and summaries of existing USDA and FDA policies and regulations; as well as those new steps planned in response to the recent findings.
The third session will provide an analysis of risk in animals and humans as they relate to product safety.
And, finally, tomorrow morning in the fourth session, FDA staff will review efforts in various parts of the Agency to reduce the potential risks of TSE agents that might be associated with regulated medical products.
And I think we must keep in mind something that is not always readily apparent, that the risk and the issues with all of these diverse products are not necessarily the same.
Okay. Later today the FDA?s Center for Veterinary Medicine will review the regulations regarding TSE and feeds, ruminant feeds, and tomorrow morning the committee will hear from the FDA?s Center for Food Safety and Nutrition regarding bovine materials in cosmetics, foods, and dietary supplements.
This is important background information, but in this meeting, really, the Committee is being asked specifically to look at the medical products issues and not to examine the non-medical products.
Also, please consider that while we know the risks associated with BSE and variant CJD can't be understood fully outside the context of risk of contamination of beef and beef products, that this Advisory Committee is an FDA advisory committee and advises the FDA and not the USDA, which is the agency responsible for most of the relevant food products.
Therefore, we ask that the Committee focus its discussion at this meeting on the science underlying FDA's regulatory policies and responsibilities rather than those of the USDA.
Well, all of that said in advance, again, I really thank not just the past and transitioning members of this Committee, but the present and future ones. We thank you for being here. We thank the invited speakers from the public, from affected industries and others for their contributions. We really welcome the input. We really need to understand BSEs better. So we welcome those contributions and a better understanding of the risks that they could pose to FDA-regulated medical products.
And what we really hope to do here is to discuss the latest science in an effort to keep us well ahead of the curve and keep medical products as safe as is possible.
So with that background, again, thanks for being here, and we really will listen carefully to your discussion.
CHAIRPERSON PRIOLA: Okay. Thank you, Dr. Goodman.
So it's important to remember that we're not here to vote on anything, just to discuss the relevant science in terms of the safeguards that are currently in place to prevent transmission of BSE or variant CJD.
So it's no voting, which is good. Don't get locked into anything.
So our first presentation will be by Dr. Robert Will, who will present the information on this possible case of transmission of variant CJD via blood transfusion.
Dr. Will, yes, please.
DR. WILL: Good morning. It's a privilege to have the opportunity to give a presentation to this Committee, and I'm going to review the evidence on the possible case of transfusion-transmitted variant CJD and then provide some background of this study and of the general situation in the U.K.
Variant CJD was identified first in 1996, and the belief then was that it was a likelihood that this was related causally to BSE, and we now believe there is now really compelling evidence that this is the case, and the presumption is that infection of humans is through food-borne transmission.
However, when variant CJD was identified in 1996, a number of issues arose about potential other routes of transmission, and therefore, in 1997, a study was set up to look at the possibility of transfusion- transmitted infection.
Could I have the next slide, please?
This was the TMER study, the Transfusion Medicine Epidemiology Review, which is a collaboration between the various blood services in the United Kingdom, the National Blood Service, the SNBTS, the Welsh Blood Service, the Northern Ireland Blood Transfusion Service, the National CJD Surveillance Unit, and the Office of National Statistics.
And in brief, the methodology of this study is as follows. Whenever we have identified a case of variant CJD which has been classified as probable in life or the minority, the very small minority of cases that are identified after death, then the details of these cases are notified to the relevant regional blood authority, and a search is made to find out whether any of these individuals had been blood donors, regardless of whether we were told that they were blood donors or not by the family.
If individuals are found to be blood donors, then a search is made for those donations to find out who the recipients are, and we keep a note of the names and details of the recipients in order that if any of those should appear in our CJD register, we would note that they had developed CJD themselves.
Now, as I say, this study was set up in 1997. It was a long-term study. There is also a safety net in that we get death certificates from the Office of National Statistics on all the recipients who have been identified in order that we can find out the cause of death, as on a death certificate, should any of them have died.
Now, we also carry out a reverse study in which individuals who are said to have received a blood transfusion ? we try and identify the donors to see whether they themselves have developed variant CJD, and I'll mention this in brief in passing, and we have also been carrying out a similar study in sporadic CJD.
Next slide, please.
On the 8th of December 2003, a death certificate was received from the Office of National Statistics which identified one of the recipients as having developed dementia and having died of this condition.
Independently of this, following the postmortem which mentioned CJD, the clinician involved reported the case to the Surveillance Unit and also tissues from the neuropathological examination were sent to the CJD Surveillance Unit for review. So we were able to identify (a) that a recipient was said to have developed CJD, and independently we had other notifications. And I think an important issue for what I'm going to say later is that there are a number of levels of surveillance by which we can identify such cases.
Next slide, please.
Now, as far as the donor was concerned, this was a 24-year-old individual who donated two units in 1996. One unit was transfused to the index case, red cells; and one unit was transfused to a patient who died of cancer after five months.
Platelets were included in a platelet pool from this donor but have not been traced, and plasma from both donations were included in different plasma pools. The donor, who was, of course, healthy at the time of the donation, died three and a half years later of pathologically confirmed variant CJD.
Next slide, please.
Now, in 1996, the recipient, age 62 at that time, was transfused five units of red cells, one from the variant CJD donor. Now, I should stress at this point that it may seem to you some of the details I'm going to give you about this case are somewhat sketchy, but that is quite deliberate because the family of the individual are very keen that they should retain their anonymity, and I am not going to go into details of the reason for the transfusion or any of the other specific details regarding this case.
The recipient developed depression six and a half years after the blood transfusion, and within months developed ataxia, painful sensory symptoms, apraxia, cognitive impairment and myoclonus. An MRI scan was said to be normal, and on review post hoc, this indeed was a normal scan, although it was only a rather simple scan without flare sequences, which have a higher sensitivity for variant CJD.
The individual died 13 months after the onset of symptoms, and the post mortem which I stress was restricted to the brain, confirmed the diagnosis of variant CJD.
In addition, the patient, was a codon 129 methionine homozygote, consistent with all of the other cases that have been tested with variant CJD to date; and was a Type 2B prion protein pattern on Western blot, which again is consistent with variant CJD and, indeed, with BSE.
There are a couple of things I should say in addition. First of all, the clinical presentation was highly suggestive of variant CJD and consistent with previous published data on this issue, and the post mortem, the regional distribution of florid plaques, for example, was typical of variant CJD.
However, because we think this may be a case of secondary transmission, further detailed studies are ongoing in order to determine that the pathology is, indeed, identical to previous cases, and transmission studies have been set up in order to identify whether the transmission characteristics of this case are similar to previous experience.
Next slide, please.
Now, statistical analysis has been done by Simon Cousens, who is at London School of Hygiene and Tropic Medicine, and he analyzed this by looking at the expected number of cases of variant CJD in the recipient population who had received a blood transfusion from a variant CJD donor in the absence of transfusion- transmitted infection. And on a crude analysis he felt that the chances that this was unrelated to the transfusion was one in 15,000; and accounting for the age of the recipient population and the age of the recipient who developed variant CJD, one in 30,000.
Now, this assumes that all of the recipients are susceptible. Now, of course, we do not have PrP gene analysis on the recipient population, and it is possible that only a proportion of them are methionine homozygotes. So one could argue that these statistical analyses are rather conservative.
So we believe that it is possible that this is a case of transfusion-transmitted variant CJD. It is, of course, impossible to exclude the possibility that both individuals were infected through dietary exposure, but we believe that this is unlikely.
Furthermore, in my view, because of this particular occurrence and the importance for public health, I think for the purposes of protecting the public it should be regarded as a case of transfusion- transmitted variant CJD.
Next slide, please.
Now, this is a shocking discovery, as Adriano Aguzzi said in his editorial in The Lancet, but he also suggested that it was not surprising, and, indeed, that has been the view of some of the individuals who we discussed this with in December. And one reason for this is this study by Nora Hunter and Fiona Houston. There have been two publications on the transmission of BSE and scrapie by blood transfusion, and I think this will be discussed later by Bob Rohwer.
But, in brief, if this is transfusion- transmitted variant CJD, it means that the donor contained infectivity in the blood three and a half years before developing clinical symptoms, and it means that the incubation period in the recipient was six and a half years.
And I would argue that these incubation periods are consistent with this study in which BSE was transmitted by blood transfusion from donor sheep during the incubation period and with an incubation period in the recipient sheep that is fairly similar to direct intracerebral inoculation.
So we think the intravenous route is probably fairly efficient, and I think that the possibility of transfusion-transmitted variant CJD is consistent with previous scientific data.
Next slide, please.
Now, one thing I should stress is that there has been one study in which blood components for variant CJD were inoculated into mice to determine whether there was infectivity in variant CJD blood, and these studies in the blood were negative, although Moira Bruce and colleagues showed that in variant CJD there was infectivity in brain and spleen. And my own opinion is that it is probable that such studies in which small volumes of blood or blood components are inoculated intracerebrally have a problem with sampling in a tissue with potentially very low levels of infectivity. And I think that this may be an important issue because I think, as far as I'm aware, this is the first evidence of transmission in humans from a low-dose tissue.
Next slide, please.
Now, just to give you the background of this study, there are 146 cases of variant CJD identified in the U.K. to date, and 136 of these were eligible to donate because they were older than 17 years.
The number of cases from whom components were actually issued that we have identified through this study was 15, and the number of recipients identified from the 15 cases, where recipient and component information is available, is 48.
Now, this is labile blood components, blood transfusion.
Next slide, please.
And these are the components that were transfused, and this is from The Lancet paper showing the year of transfusion, the component transfused, and the number of recipients. As you can see, there were a whole range of materials transfused, but the great majority were red cells.
Some of these were later leukodepleted. This was introduced around 1998 in the U.K. to try and minimize risk, but many of the individuals were exposed to red cells that were not leukodepleted, including the case I have just described.
We have an important question as to whether leukodepletion may have reduced the risk of transmission of variant CJD, and my own opinion about this is that the evidence on this is somewhat uncertain, and I do not think we can assume that leukodepletion will have removed the risk of transmission.
Next slide, please.
Here's the age of the transfusion recipients, the 48 patients, and as you can see, the great majority of these individuals were in the older age groups. This is important partly because in the U.K. it is very unlikely that any of these individuals would themselves act as blood donors because of their age. And, in fact, none of the individuals who were identified through this process have themselves acted as blood donors in the U.K., to our knowledge.
Next slide, please.
Now, I'm sorry about this slide, but this is showing the dead recipients; that is, 31 individuals who were recipients of a labile product from a variant CJD donor have died. The great majority of them have died within two years, and in fact, the absolutely majority within one year of the transfusion, and this reflects the severity of the underlying disease process.
But it also means that, if the incubation period by blood transfusion was measured in six, seven, eight, ten years -- we don't know -- it is very unlikely that any of these individuals would have had time to develop variant CJD.
The blood components transfused are listed here, and the interval between donation and onset of clinical symptoms in the donor are listed here.
Now, because of the methodology of this study, all we have on the individuals who have died is the cause of death on a death certificate, and you can see the list here if you can read it. Cancer figures prominently, of course, not surprisingly; a number of hematological conditions; but in the patients who survive for longer, there are other conditions, such as ischemic heart disease, bronchopneumonia, chronic obstructive airways disease, and of course, dementia in the index case I have described.
So how confident are we that none of these other individuals have developed variant CJD? Well, I have given you the information that is available on these cases. For ethical reasons we have not been able to track them in anymore detail, but I stress that we have a number of levels of surveillance, including direct referral of cases if there's a suspicion of CJD, and a neuropathological network such that brain tissue will be sent to the Surveillance Unit if any such patient dies.
So we cannot be certain about these individuals. All I can say is that we have no good evidence that any of these other individuals themselves developed variant CJD.
Next slide, please.
We have 17 individuals who are alive, having received a transfusion from a variant CJD donor; and this is the list. This is the current age in these individuals, the time elapsed since the transfusion, the blood component transfused, and the interval between donation and onset of clinical symptoms in the donor, which may be an important parameter in relation to risk.
I stress that we have two cases with a minus here, minus three months and minus five months. This means that the individuals were actually suffering from variant CJD at the time they donated blood, but it is highly unlikely that these individuals could have been identified at the time they were donating blood as suffering from variant CJD because of the nature of the clinical presentation in variant CJD. It presents with nonspecific psychiatric symptoms which are insidious in onset and often progress, and it may be six months on average before any neurological signs develop.
There is a possibility, however, although we do not know for sure, that the closer you are to clinical onset when you donate blood, the higher the risks that the blood will contain infectivity.
Next slide, please.
Here is the time elapsed in these 17 individuals since the transfusion, and as you can see, a significant proportion of them have survived only for a limited period in relation to the one case in which variant CJD developed after six and a half years. But we do have a number of individuals who have survived for longer and have not yet been identified as suffering from variant CJD, and to our current knowledge are not suffering from variant CJD. The longest survival in this group is 11 years.
Just in passing I should mention that the ethical issues in relation to this study have been discussed repeatedly. We got ethical permission to do the study originally in 1997 and received separate ethical permission to flag the individuals with the Office of National Statistics.
Our original ethical permission was that we would not inform the recipients that they had received a potentially contaminated blood transfusion. However, in our original ethical form, we put in that if there should be a test, if there should be a treatment, or if evidence should evolve of a risk through this route, then the whole ethical position would be reviewed.
And, in fact, independently of this study, the CJD incidence panels in the U.K. had decided that individuals in this situation should be informed. And since December the 8th, all of these individuals -- or measures have been put in place to inform all of these individuals of the risk.
That having happened, four of the individuals have already contacted either a neurologist or the Surveillance Unit directly because of extreme concerns about the situation that they are in.
Next slide, please.
Now, this issue has caused public concern in the United Kingdom. Here is December the 18th, the day after the announcement in the House of Parliament, "CJD Time Bomb: Hundreds Face Wait."
Next slide, please.
"Thousands at risk of vCJD from Blood Transfusion."
And, of course, the question is: What is the risk to the U.K. population? We do not know how many individuals are incubating variant CJD and may be acting as blood donors. So there may be a population of individuals who have been exposed to blood transfusion that would not have been identified by the TMER study.
Next slide, please.
The only evidence we have on this, and I'll just discuss this briefly is evidence from a surveillance system run by James Ironside and Dr. Hilton of appendicectomy and a smaller proportion of tonsillectomy samples in the U.K. general population that have been analyzed to determine whether there is evidence of immunostaining for prion protein in these samples.
And this was published in 2002. The interim results: one out of 8,318 positive with an estimated prevalence of prion protein accumulation of 120 per million in the U.K. population, but as you can see, with very wide confidence intervals of .5 to 900. And this study is ongoing.
Next slide, please.
Now I mentioned already that two of the units from the donor have been sent for plasma fractionation, but in fact, we now know that 20 units from vCJD donors were sent for plasma fractionation in the U.K., and this means that thousands of individuals were potentially exposed to products derived from plasma fractionation in which a pool will have been contaminated with a vCJD donor.
We do not have a surveillance system in place to identify these individuals.
One thing I should say, of course, is that sourcing of plasma for fractionation in the U.K. was introduced during 1998 because of the theoretical risk, and this involves importation of plasma from the United States in England and Wales, and from the United States to Germany and Scotland, which would suggest that the risks from plasma originating in the U.K. in relation to fractionated products has been stopped since 1998.
However, there were individuals exposed prior to that date, and looking through the surveillance system information, we have no case of variant CJD with a history of exposure to fractionated plasma products to date, and indeed, one could argue that the risk from fractionated products are likely to be much less than from labile products because of processing and perhaps because of the volume to which patients are exposed.
Now, this is the reverse TMER. This is individuals who were said to have received a blood transfusion. This is derived from information from the family, and it is very difficult to check in the same way as we can with blood donations. In these, four records have been found of individuals with variant CJD who had received a blood transfusion, 117 components received, 111 donors traced, and none of them are on the Surveillance Unit register.
Next slide, please.
Now, it's not my role today to discuss the evidence in relation to sporadic CJD. This is going to be done later, I think, this morning, but just to stress that in relation to sporadic CJD, the evidence on iatrogenic transmission -- this is a summary slide from Dr. Brown from last year -- all of these cases have involved implication of tissues either in or adjacent to the central nervous system. And within the surveillance system, the U.K., Europe, and other studies, which I think will also be discussed, we do not currently have evidence of transmission of sporadic CJD through blood transfusion.
Next slide, please.
We have done a similar study on sporadic CJD, and this is somewhat unsatisfactory data. What we do is we take sporadic CJD cases and controls, as we have also done with variant CJD. This is a blinded study. We found 224 components that have been donated, 65 recipients have been traced, and none are on the Surveillance Unit register.
One of the reasons why there is only a small proportion that has been traced is because sporadic CJD cases tend to be very much older than variant cases and may have donated decades in the past, and it's very difficult to track these donations because of the record system.
We also have a reverse study in sporadic CJD, which is also negative.
Next slide, please.
Now, just briefly at the end to summarize the overall situation with variant CJD, we have 146 cases in the U.K. to date, 82 males, 64 females, and all tested cases are methionine homozygotes on codon 129 of the PrP gene.
Next slide, please.
One hundred and three are neuropathologically confirmed. Seven are alive currently.
Next slide, please.
This is the age distribution of variant CJD cases, of the 146, and as you can see, the great majority of cases are age less than 40 at death or are currently alive, and cases over the age of 60 are extremely rare on current evidence. And it's important to stress that the recipient I described earlier was in their late 60s when they died, which is unusual for presumed food-borne variant CJD.
Next slide, please.
The trends in the U.K. are very important in relation to assessing the potential risk of secondary transmission. Here are the number of deaths per annum of variant CJD in the U.K. showing the steep rise and then the decline or a possible leveling off in the last year.
Next slide, please.
This is the number of onsets of variant CJD per annum in the U.K. showing a rather smoother pattern with this increase and then a decline which seems to have been sustained.
I should just stress that we identify about 95 percent of cases within a year of onset. So this Figure 14 is almost certainly nearly complete. This is reassuring data, but, of course, is not definitive because of the possibility of second waves either due to different exposures -- I mean different patterns of dietary exposure or perhaps in relation to different genotypes being susceptible.
Next slide, please.
This is the latest statistical analysis from January. This is the exponential trend in relation to the onsets. The next slide is the same data with a quadratic trend, and this is a better fit, suggesting that. in relation to onsets, there is a significant decline in the U.K. currently in variant CJD.
Next slide, please.
This is the deaths, and there's an equally good fit between a quadratic model with a decline and a plateau model. So there is uncertainty in relation to the deaths about the trend in the U.K.
Next slide, please.
vCJD worldwide, September 2003; this has been updated. One hundred forty-six cases in the U.K., six in France, one Republic of Ireland, one Italy, one USA, one Canada, and of course, the case in the Republic of Ireland, USA, and Canada had a history of residence in the U.K. and could have been exposed to BSE in the U.K. And indeed, in my view is far more likely than the exposure in the Canadian and the American cases were in the U.K. than anywhere else.
That is not true of the French and Italian cases that were exposed almost certainly in their own country.
Next slide, please.
This is the duration of residence in the U.K. and the U.S., Canadian, and Irish case. The Hong Kong case is classified as U.K. because it developed the disease while resident in the U.K., but as you can see, at least on this data, it looks as though individuals who were exposed to BSE in the U.K. required an extended period of residence to be exposed sufficiently to cause disease.
Next slide, please. I'm nearly at the end.
I just thought I'd better mention something about the perspective in other European countries, and this is the BSE epidemic, which is not quite up to date in some countries in Europe. And this shows a pattern in Portugal which looks like this.
In Switzerland, which has an excellent surveillance system, there was an increase and a decline, and then as you can see, an increase again around 1999-2000, which was due to the introduction of active testing rather than passive surveillance for BSE.
The pattern in some other countries is very unusual for an infectious epidemic. Germany had a sudden increase in the number of cases; similarly in Spain and Italy, and it is probable that this was due to the introduction of active testing, with the implication that it is possible that cases of BSE were missed in those countries by passive surveillance during the 1990s.
The reason I mention this is that it's often asked whether we're going to see other cases of variant CJD in Europe, out with France and U.K. and Italy. My own opinion is that it is probable that in some of the European countries the dietary exposure of the human population to BSE was later in the U.K., and it is too early to say that those countries will not themselves get variant CJD, albeit in very much lower numbers than in the U.K. in relation to the potential exposure.
Next slide, please.
These are the acknowledgments within the Surveillance Unit: James Ironside; Richard Knight; Hester Ward; Jan Mackenzie, who has been coordinating the study and the TMER since we started in May 1990; Sarah Cooper and Craig Heath, who do all of the work; they're the registrars; the National Blood Service, Pat Hewitt and Charlotte Llewelyn; and the SNBTS; the Northern Ireland Blood Transfusion Service; and the Wales Blood Transfusion Service.
However, I think I'd like to finish by stressing that none of this research would be possible without the cooperation of the families of patients with variant CJD who allow us to forward details to the National Blood Services, and I'd particularly like to acknowledge the family of the index case of the recipient who were good enough to give us permission to publish the case and also to discuss it at meetings like this.
Thank you very much.
CHAIRPERSON PRIOLA: Are there any questions for Dr. Will from the Committee? Yes, Dr. Wolfe.
DR. WOLFE: Dr. Will, of the 30 or so people listed in, I guess, your Table 2 in the paper, of people who died who turn out to be recipients, how many of them have had pathologic examination of the brain looking for prion protein A and B? Since this index case, are you thinking of changing the surveillance system with respect to looking for that? With this intriguing group of people, you might be able to find out more about latency period.
DR. WILL: Yes. I mean, I think they're both very important questions. The answer to the first question is that because of the ethical strictures on the study, which I think were entirely appropriate, we do not have information on neuropathology on those that have been certified and have died.
The actual rule of the ONS is that if we are to do this study, we are not allowed to use the death certificate to retrospectively go and discuss things with the family or the clinician. So we could not do that.
However, I think the point that we may need to change that in order to obtain more information is under active discussion. Although one thing I would say is that -- and perhaps this is a bit self-serving -- but I think it really does show that surveillance systems can be important in identifying actual risks, and it's important to have these different levels of surveillance, and I personally think that it is quite likely that we would have identified the variant CJD in one of those recipients if it had happened, although, of course, I can't be sure, and actually taking further action to be certain about that is a very important issue.
CHAIRPERSON PRIOLA: Dr. Bracey.
DR. BRACEY: Yes. In terms of the index case, there were two components. One went to the patient with pancreatic cancer. Which of the donations was the first donation?
And kind of aligned with Dr. Wolfe's question, are the materials available from that patient pathologic materials?
DR. WILL: I didn't say pancreatic cancer. I think I just said cancer.
DR. BRACEY: Cancer, okay.
DR. WILL: Yes, who died five months afterwards. Well, I think, but I'll have to confirm to you, that the first donation was to the index case and the second donation was to the other individual, but I can check that and let you know, but I think they were both given, you know, within a relatively near period.
And the other question was in relation to?
DR. BRACEY: Oh, well, the other question actually relates to the counseling system. One of the real challenges that we face in the states ? we currently have systems where there are recalls for patients at risk for CJD, with the notion that there might be some discussion, but in truth, the many physicians at the bench level out in the field really don't know how to counsel folks with regard to issues related to CJD.
So I'm kind of intrigued in terms of how you all have set up your system so that you have an effective counseling system.
DR. WILL: Well, I think that's a critically important issue. I would agree with you that it is extremely difficult for most doctors to counsel people on this issue because they don't have the relevant information.
In the U.K. with the 17 individuals who were informed, some information sheets were produced and were provided to the relevant doctors in order to counsel the individuals, but this does have difficulties because most doctors, even with an information sheet, may not be fully informed as to what to say.
What actually happened with the cases I have mentioned who contacted a neurologist is that the neurologist phoned us up and asked us about the details of the study and what we would say about it, and then discussed it with the individuals.
And I cannot help but agree with you that it is a major challenge as to how to inform these individuals in a sensitive way that allows them to have accurate information.
So I think that thinking about that in advance is a very important issue if you're going to inform members of the general public of a specific risk.
CHAIRPERSON PRIOLA: Dr. DeArmond.
DR. DeARMOND: Hi, Bob. The question I have is regarding the older age people who died of variant CJD. Maybe you mentioned it. How many of them had a transfusion history, since the three over the age of 60 is unusual, and the ten over 50 is even somewhat unusual?
DR. WILL: Yeah. The oldest individual who died at the age of 74 did not have a transfusion history, and I don't think the other 60 year old did either. And, of course, if those individuals had themselves developed variant CJD with a history of transfusion, we would have known that from the study.
So I don't think that you can say -- I understand exactly what you're saying, Steve. The implication could be that this was transfusion- transmitted. We don't actually believe that in relation to the evidence that we have in relation to those cases.
CHAIRPERSON PRIOLA: Dr. Nemo
DR. NEMO: That was an excellent presentation, Dr. Will. Thank you.
One question I have is your platelet components. You didn't trace them in the index case, and I noticed in all the other traces that there are very few platelet components. Is there a problem tracing platelets?
DR. WILL: I'm not an expert at this, but I believe that, of course, this sounds like a very simple study. You just find out who received the donations and then you compare it with a list.
But in fact, it took an enormous amount of work by the National Blood Service going down to the level of hospital notes. And, of course, the confirmation that individuals received a blood transfusion depends on the quality of the notes themselves.
My understanding, although as I say I'm not expert at this, is that tracing platelets is particularly difficult in relation to this, although in that one case that I had mentioned up there, active efforts are still being made to try and trace that, but I think it is more difficult than it is with actual blood donations, perhaps because of the difficulties in record-keeping and following things up.
CHAIRPERSON PRIOLA: Dr. Nelson.
DR. NELSON: Yes. Some of the studies in sheep that were transmitted by blood transfusion, I think they reported less prion in the peripheral tissues and just were limited to the central nervous system than the oral, than those transmitted orally, and I wondered if you had any data.
I realize you said that the autopsy was limited, but I wondered even prior to the autopsy was there any data about the distribution of prion in this human case that was probably transfusion-transmitted.
DR. WILL: Sadly, we do not have any information on that, and my understanding is that even though there is PrP in fairly high levels in variant CJD in peripheral tissues, this does not have any clinical accompaniment. And it is unfortunately the case that a brain-only post mortem was carried out, so we do not know about the levels of PrP in the peripheral tissues in this case.
However, I think that Dr. Lasmezas and colleagues did publish an article in The Lancet, the same issue of The Lancet, suggesting that in their experiment with intravenous inoculation of brain, I think, that there was significant PrP presence in peripheral tissues, including the gut.
CHAIRPERSON PRIOLA: Dr. Gambetti.
DR. GAMBETTI: Bob, what are your thoughts about the fact that out of 15 donors with variant CJD and 48 recipients, only one case really came down with variant CJD acquired from the transfusion? What do you think is the factor that may have limited this phenomenon or the factor that allowed the phenomenon to occur?
DR. WILL: Yes. Well, firstly, there are a significant proportion of the 48 recipients who did not survive long enough to observe variant CJD, should it have occurred, because of death due to the underlying illness.
Secondly, the study is not yet complete because we have 17 individual who we know received the blood component who are still alive and who, sadly, I think are at greater risk of developing variant CJD.
The incubation period by intravenous transmission may be very variable, and we simple cannot know whether individuals have survived long enough after the transfusion to suggest that they're not going to get variant CJD. And, of course, as I showed on the slide, a significant proportion of the 17 have not yet survived the six and a half years, which is the presumed incubation period in the index case.
So I think, firstly, we cannot say that one out of 48 is the final figure, nor may it be an accurate reflection of the relative risk.
The other variable, of course, is the time that the blood was donated in relation to clinical onset in the donor, and some of those intervals are really very long before clinical onset, and although there is contradictory data in the scientific literature, it is possible that infectivity in blood may be present particularly near clinical onset rather than many years prior to clinical onset.
There's also the possibility that infectivity in blood may be intermittent. We don't know that it's consistent throughout the incubation period. So it could be that some of those donations from variant CJD donors didn't contain any infectivity.
The only relevant data that I have in relation to that is the fact that we did identify an appendix specimen from an individual who had died of variant CJD I think about ten years prior to clinical onset, and James Ironside stained that for PrP, and it was negative.
So there are a number of variables that we cannot control for, and I'd very much like to say that the risk is one out of 48, but I don't think we can say that at all.
CHAIRPERSON PRIOLA: Dr. Bailar.
DR. BAILAR: I have a question about the completeness of your register. Do you think it's at all likely that any recent cases have been missed, misdiagnosed or not reported?
And what about 5, 10, 20 years ago, before people were as sensitive to this?
DR. WILL: Well, I'll deal with the first one first because the issue of whether variant CJD was around many, many years ago is an important question not only in relation to this study, but in relation to the hypothesis of a link with BSE.
So that has been looked at in a number of ways. One of the ways of looking at it is the hallmark of variant CJD is the neuropathology, and James Ironside has looked extensively in the past in relation to previous cases that we knew about, and we did that before the paper was published in 1996. Any young cases with neuropathology were reviewed in order to see whether there was evidence of florid plaque deposition, and that included a 16-year-old who died in 1986, pre-BSE. Slides from that were reviewed, and it was sporadic CJD.
There's a thing called the National Retrospective Review, which is coordinated by James Ironside in which they're reviewing available neuropathology specimens going back in the past in the U.K. to restain them, and no case of variant CJD has been found.
In Europe, Herbert Budka coordinated a system to try and review all of the cases they had in various brain banks in Europe to identify past cases of variant CJD and nothing was found. So from the perspective of neuropathology we think it's a new disease.
Secondly, two studies have been done in the U.K. using death certificates to identify cases that could have been miscertified as variant CJD in the past, one by Dr. Majid (phonetic), which found no evidence of anything that could look like variant CJD after review of case loads, and a study in Wales when they went back in the past and obtained neuropathology tissue to restain in a small minority, and again, there was no evidence of past cases of variant CJD.
So I think the current evidence suggests that this is, indeed, a new disease that developed in the U.K. in the mid-1990s.
Are we missing cases through our surveillance system? Well, of course, we cannot be 100 percent certain that we are not missing cases. However, we have a number of levels of surveillance starting off with the direct referral system. We have a very high postmortem rate in suspects, in about 80 percent of suspects. There is a Neuropathological Network such that if any case of CJD is identified in the U.K., it is referred to the Unit.
And we obtained, again, death certificates mentioning CJD throughout the U.K., and if we have not identified the cases, we go back and find out from the clinical notes and, if available, neuropathology whether it was CJD.
And I think I am confident that in the age range of individuals who would be seen by a neurologist, we are confident we have very good ascertainment.
We have a separate system for pediatrics called the PIN (phonetic) system, which has identified six individuals under the age of 16 years at onset with variant CJD. So we are confident that we are identifying children.
The issue that does arise, and I think it's an important issue which I suspect is why you're asking the question, because of the age of this individual, is: Would we be good at identifying cases in the elderly?
And that is a question that is difficult to answer, and we are considering mechanisms for trying to set up a pilot surveillance system in the elderly to insure we're not missing variant cases in that age group.
DR. BAILAR: Thank you.
CHAIRPERSON PRIOLA: Mr. Bias.
MR. BIAS: I was curious. Since the donor was of a younger age, how do you handle their other medical care, let's say, surgery, dental care, if they happened to like tattoos?
DR. WILL: Well, in relation to the 17 individuals who have been informed that they received a potentially contaminated blood transfusion, one of the reasons for informing these individuals was to insure that they did not act as blood or organ donors.
There are a number of other potential mechanisms by which these individuals could undergo invasive procedures during dentistry, as you mentioned, and of course, a number of other procedures, and the CJD Incidence Panel from the Department of Health in London has been set up specifically to discuss these particular issues.
And a document in relation to blood itself, I think, will be shortly released by that group. My understanding, although I'd have to confirm this, is that the general views of the risk from dentistry are probably very low indeed.
We've done some epidemiological work, limited as it is, because of relying on dental histories from families, but we've not found any evidence of transmission of variant CJD through dentistry, although the information is limited, and there have been some studies of dental pulp, both in sporadic and variant CJD, which do not show immunostaining for PrP.
But it's a very important question, and there are a range of other issues that could be discussed. One of them, just to mention in passing, relates to the use of tonsillectomy instruments in the U.K. because, of course, the tonsils contain quite significant amounts of PrP in variant CJD, and the individuals who undergo tonsillectomy are often children. And in the U.K. it was decided some years ago that they would try introducing disposable tonsillectomy instruments in order to mean that they were one-use and, therefore, no reused on subsequent patients.
But, sadly, that resulted in complications with a higher risk of post operative hemorrhage and possibly one death, and that policy was reversed. And I think this underlines the enormous difficulty in dealing with public health issues in relation to variant CJD, particularly in relation to medical issues like blood transfusion, because any action that is taken can have a very negative effect on public health as well as minimizing the risk.
CHAIRPERSON PRIOLA: Dr. Bracey.
DR. BRACEY: I may have missed this, but did you provide any information on the interdiction efforts regarding the pools, the pooled products that the plasma went into?
And is there a study, an infectivity study in progress with any of that material?
DR. WILL: As far as I'm aware there is not an infectivity study specifically in relation to that material. However, I do believe that there are plans to do, say, extensive studies using the BSE sheep transfusion model in relation to looking at the plasma fractionation.
In relation to the withdrawal of plasma fractionated products in which there was a variant CJD donor, that, indeed, did happen very early on in variant CJD, within two years of the first case. We think there may be -- I can't remember exactly if it's two or three withdrawals of plasma fractionated products.
Of course, because of the time lag between the donation and the onset of variant CJD, in many cases the products had already been used up. However, there have been at least two or three occasions in which there was extant product potentially contaminated with variant CJD, including, I think, Factor 8.
And the clinicians who were informed about this usually took the decision to inform the individuals to remove the potentially implicated Factor 8 and to get rid of it.
Of course, this does raise another issue which you raised before about what do you tell people, and I think it's a very important issue.
CHAIRPERSON PRIOLA: Okay. Thank you, Dr. Will. You'll be around for most of the rest of today; is that right? All right. So if the Committee has any more questions, he'll be available.
Thank you very much.
Our next speaker will be Dr. James Sejvar.
DR. SEJVAR: Good morning. It's a pleasure to have the opportunity to speak to the group this morning about the various surveillance activities that we at CDC conduct for Creutzfeldt-Jakob Disease.
I will mention that basically surveillance for CJD was enhanced back in 1996 due to the emergence of variant CJD in the United Kingdom, and basically since that time, CDC has undertaken a number of different measures to increase surveillance ability for CJD, both classic and variant, in the United States.
And so what I'd like to do in the next 15 minutes or so is to give you kind of a quick overview of the surveillance mechanisms for CJD and to suggest to you that the evidence from this surveillance indicates that we are not observing an increasing rate of CJD in the United States, nor the emergence of variant CJD.
Next slide, please.
One thing that's probably important to keep in mind as I speak is that there's a number of different features of CJD as a disease entity that make it somewhat difficult to conduct surveillance for. So basically in an attempt to circumvent some of these problems, CDC takes basically a multi-pronged approach to the surveillance for CJD, and the core mechanisms that we employ include periodic reviews of the National Mortality Database, collaboration with state health departments to perform active case review of CJD decedents age less than 55 years, and the establishment and support of the National Prion Disease Pathology Surveillance Center, which is headed by Dr. Pierluigi Gambetti at Case Western Reserve University.
Now, additionally, in association with several other organizations, including FDA, we collaborate on special surveillance projects involving groups of persons thought to be of particular public health concern, and this includes, for instance, recipients of human growth hormone, and as I'll talk about a little bit later, recipients of blood transfusions.
And then finally, we respond to spontaneous reports provided to us by clinicians and others.
Next slide, please.
Now, one of the cornerstones of our CJD surveillance entails review of the National Mortality Database, and this has been ongoing for many years. Now, basically to perform this surveillance, we utilize data provided by CDC's National Center for Health Statistics, which basically keeps a very large database encoding death diagnoses for the entire U.S.
And there's actually several features of CJD that lend themselves very well to this type of surveillance. Now, first of all, this is a disease with essentially 100 percent fatality rate, and as a result, once a diagnosis is made, it should make its way into this database, and further a clinical diagnosis of CJD is actually much more accurate towards the terminal stages of the illness, and so as a result death information on this illness is actually fairly reliable.
Now, our continued assessment of this data suggests several things. Now, first of all, it seems it's clear that since the early 1980s, reported rates of CJD in the United States have remained stable over time, and cases basically continue to occur at a rate of about one per million population, and the median age at death in the United States remains at about 68 years. And basically neither this median age at death nor the rates have shown any significant change over time.
Now, additionally, nearly all decedents have been over the age of 45 years, and basically we have had no reports of CJD among teenagers, nor have we seen rate increases among younger age groups. And basically this provides evidence that we are not witnessing the appearance of variant CJD nor the emergence of CJD in basically atypical age groups.
Now, I'd like to show you a graph that I think is very illustrative, and basically it displays the age distribution of cases of variant CJD in the United Kingdom over in the yellow, compared with that of sporadic CJD in the United States.
And I think that you can immediately appreciate that one of the distinctive features of variant CJD in the United Kingdom and elsewhere is the young age at death compared with that of CJD in the United States.
Basically the vast majority of deaths from variant CJD occur in very younger age groups; while for cases of CJD in the United States, cases younger than 45 are extremely rare.
Next slide, please.
And so basically CDC has utilized this fact to pursue enhanced surveillance among U.S. CJD cases aged less than 55 years in an effort to detect the emergence of variant CJD.
Now, in collaboration with state health departments, we obtain and review the medical and neuropathologic records of CJD cases aged less than 55 years, and to date, we have reviewed 165 such cases occurring since 1994. Now, 80, a little less than half, of these cases have had either brain biopsy or more typically autopsy to confirm the diagnosis of CJD. And, more specifically, since the first detection of variant CJD in the United Kingdom, basically all U.S. CJD cases under the age of 30 have been autopsied, and basically to this point there has been no histopathologic or clinical evidence that any of these cases has been attributable to variant CJD.
Now, another important piece to CDC's surveillance activities has been helping to establish and support the activities of the National Prion Disease Pathology Surveillance Center. This was done in collaboration with the American Association of Neuropathologists back in '96 and '97. And basically the Center offers advanced diagnostic testing for prion diseases and serves as a way of confirming suspected diagnoses, as well as detecting emerging forms of prion disease, including variant CJD by pathology.
Now, clinicians are basically encouraged to provide brain tissue from biopsy or, again, more typically autopsy from patients with suspected prion diseases, and in this way basically one of the important aspects of the Center is that it provides basically a free state-of-the-art diagnostic testing service for referring clinicians.
Now, one thing that's critical for the success of the Center is the performance of autopsies in suspected cases of CJD, and so basically we're actively collaborating with various sites to increase the generally declining rates of autopsy performance in the United States.
But what's clear at this point, however, is that with the exception of the one U.S. case of variant CJD which epidemiologically is felt to have been acquired in the United Kingdom, of the over 1,200 specimens reviewed by the Center to date, there has been no evidence of variant CJD in these cases by histopathology. And so basically this data is reassuring.
And so I think basically you can appreciate that there are several lines of epidemiologic and laboratory evidence from CDC's various surveillance activities to suggest that we have not seen the emergence or the appearance of domestically acquired variant CJD in the United States.
Now, one of the other things that I was asked to comment on this morning and specifically address is the epidemiologic data regarding risk of acquisition of CJD through blood transfusions. Now, obviously this concern -- next slide, please -- this concern has been ratcheted up quite a bit since the recent events in the U.K., which Dr. Will has just explained in detail.
But what we can say is that the epidemiologic evidence continues to suggest that the risk of transmission of sporadic or classic CJD in the United States from transfused blood is low or absent.
And there's actually several lines of epidemiologic evidence to suggest this, and I'd like to sort of walk you through those at this time.
Now, first of all, to this point there has been no case reports of a case of classic or sporadic CJD related to transfused blood. Now, in addition, several case control studies have been conducted among patients with sporadic CJD. Now, in addition to other potential risk factors, the risk of blood transfusions has been repeatedly assessed by these studies, and really at this point none of the current seven studies provides any evidence of a risk of transfusion in classic CJD.
Now, additional epidemiologic evidence is provided by CDC's data from the National Mortality Database. Now, as I mentioned before, we have not seen any significant changes in rates or demographics over time of cases of CJD in the United States, and, again, no cases of CJD have been observed in teenagers, a group likely to receive blood products as well as albumin derivatives and immunizations, and importantly, among all of the CJD decedents in the database, none has had a co-diagnosis code of hemophilia, sickle cell disease, or thalassemia, basically groups who obviously receive multiple and frequent blood transfusions and blood products.
Now, there's additional evidence provided from a study initiated jointly by the American Red Cross, CDC, and the now inoperative National Blood Data Resource Center, and this is a study that has basically been ongoing since 1995. And basically the study has identified 331 transfusion recipients of blood components from 25 known CJD-implicated donors, 16 of which have been pathologically confirmed.
Both look-back studies and prospective data is available on this group, and of 236 deceased recipients, none has died from CJD.
Additionally, about 116 long-term survivors, patients surviving greater than five years, have been identified from this group, and this includes 84 who are currently still alive, as well as 32 who are now deceased.
The median survival time for these patients was nine and a half years post transfusion. Now, additionally, 17 of these patients had survival durations greater than 16 years, and three have had survival durations of greater than 26 years.
Now, given the fact that iatrogenic CJD generally has an incubation period of less than 13 years, sometimes as short as one, one and a half, or two years, while not definitive, the evidence from this study is certainly reassuring.
Now, a similar, albeit much smaller assessment was conducted among 27 known recipients from a single donor with sporadic CJD in Germany, and again, no evidence of CJD detected among 18 deceased and nine living recipients.
Now, finally, persons with hemophilia who would be expected of being at much higher risk of the development of transfusion-related CJD have been closely assessed by a study conducted by CDC's Hematologic Diseases Branch and the Hemophilia Treatment Center's group. And essentially there have been no cases of clinical diagnosis of CJD among over 12,000 patients with hemophilia who have been assessed since 1996.
Now, additionally, 40 decedents that were identified from this group have undergone brain autopsy, and among these 40 cases there has been no evidence of spongiform changes on histopathology, suggesting that these patients were not harboring subclinical or early stage CJD at the time of their death.
So, again, more supportive evidence against blood transfusion as a route of transmission of sporadic CJD.
Now, the reason that variant CJD has been able to make this jump is unclear. There are several hypotheses and perhaps some of these will be touched upon during the course of this conference. It may have to do with the differing physical chemical properties of the variant CJD agent. It may be that the oral route of transmission of variant CJD is more likely to lead to a blood phase, so-called "prionemia." Or the fact that the agent is in such high concentration in lymphoid tissue.
But basically what we can say is that the available epidemiologic evidence suggests that the risk of transmission of sporadic or classic CJD through blood appears to be extremely low, if it exists at all.
And I will close my talk there and take questions.
CHAIRPERSON PRIOLA: Dr. Gambetti.
DR. GAMBETTI: I think that the data that you presented are very reassuring, but from the perspective of the Nation Prion Disease Pathology Surveillance Center, we feel that really the final answer as to the presence or absence and the actual number of cases of sporadic or familial CJD will come out only if we can expand the number of cases that we examine by tissue analysis.
And, therefore, as you recommended, I would like to underline further the need really to increase the number of autopsies in cases of suspected CJD and if the autopsy is done, make sure that the complete examination is carried out so that at least we should be able to examine about 70, maybe even 80 percent of the cases, as is done in several European countries, and then be able to examine very carefully the clinical data of the remaining cases in which autopsy for various reasons cannot be performed.
I think this really is what we should try to achieve here in the United States following the example of the European countries.
CHAIRPERSON PRIOLA: Dr. Linden.
DR. LINDEN: Thank you very much for an excellent presentation that touched on some very important points. I agree with my colleague about the importance of tissue pathological diagnosis as a contributing factor, but I also commend CDC for putting in resources to some very important epidemiologic studies which I think are a very important contribution to this. And I would certainly encourage ongoing work in that area.
I also thought that many of your slides were very nice slides, with the exception that thalassemia wasn't spelled correctly.
DR. SEJVAR: Sorry about that.
DR. LINDEN: But I did not see that they were in our packet, unless I missed them. Would it be possible for us to get a copy of those? That would be very helpful.
DR. SEJVAR: Absolutely.
DR. LINDEN: Thank you.
CHAIRPERSON PRIOLA: Go ahead.
DR. BRACEY: The question I have relates to -- I had a telephone call, so sorry. I may have missed this. Is there a system in place that tracks ‑- obviously there has been no variant CJD, but tries to link transfusions to cases? Are we looking at CJD and previous transfusions?
DR. SEJVAR: Basically, we are looking at -- when a case of CJD is identified, we do go back and look at transfusion records.
DR. BRACEY: I guess, then, perhaps a comment. One of the things that we've, I guess, found through our experience with HIV is that sometimes, based upon the weaknesses of our system for tracking, that can be somewhat difficult. We're not a point right now where this perhaps would be so critical, but I think one of the things that we may need to look at in the future is the capability of our system to allow tracking, complete tracking.
DR. SEJVAR: And I think as Dr. Will alluded to, sometimes that is not as easy an endeavor as it kind of appears on the surface, but I agree with you that, in anticipation, that is something that we are focusing on.
CHAIRPERSON PRIOLA: Dr. Bailar.
DR. BAILAR: How long does it take on average after diagnosis or after death for a patient to get into your data system?
DR. SEJVAR: The lag time is probably within a year.
DR. BAILAR: Would a shorter time be helpful? Obviously, it would be a little help. Would it be significantly helpful?
DR. SEJVAR: Basically, since we're following this data over time and given the nature of CJD as an illness, I don't really think that decreasing that lag time significantly is going to make a significant change in surveillance.
DR. BRACEY: Thank you.
CHAIRPERSON PRIOLA: Dr. Hogan.
DR. HOGAN: Thank you for this great presentation.
Of course, all of us are concerned about the issue of under-reporting of cases of CJD, not only cases of known CJD that are not reported or analyzed, but cases that are misdiagnosed as perhaps dementia, and other problems in which CJD is never brought up.
So are there methods in place from CDC or the Prion Unit to address these issues or any way that we can tighten up the reporting issues? Have you thought about this or is there anything planned?
DR. SEJVAR: Well, you know, again, as Dr. Gambetti mentioned, you know, the key is the pathology. Do you know what I mean? There are going to be cases that are misdiagnosed, and you know, the bottom line is to try and increase the available pathologic data on these cases.
Certainly, there are cases that are misdiagnosed. On the other hand, as I mentioned, you know, by the time a patient with CJD is in the terminal stages, the clinical diagnosis is actually fairly good. So I think the key is, as Dr. Gambetti mentioned, pathology.
CHAIRPERSON PRIOLA: Dr. Linden.
DR. LINDEN: Yes. Following up on the question about reporting, I think you assumed 100 percent reporting into your death database. Since I work for a state health department, I am somewhat familiar with vital statistics reporting.
Do you feel that you get 100 percent death certificate reporting from all 50 states?
DR. SEJVAR: We actually tried to address that at the onset of enhanced surveillance, and basically we went back and basically did a population-based assessment, basically seeing what results we are getting from the National Mortality Database compared to active case finding within a defined population, and we were finding that basically we were getting over 85 percent ascertainment through the National Mortality Database.
You know, so again, we are confident that we are catching the majority of cases in this manner.
CHAIRPERSON PRIOLA: Dr. DeArmond.
DR. DeARMOND: If I could partially answer the question that Nick Hogan asked, one of the studies that was done by the CDC was to look at hemophiliacs who had become demented so that the idea was to sort out what was the cause of the dementia in those patients. These are young people who had received transfusions for many, many years.
And as I recall, 95, 98 percent had died of HIV-related problems, and then a couple of the others ended up dying of hepatic encephalopathy, and no evidence by prion protein analysis or by histopathology of CJD.
So they were addressing the issue of dementia in this population also. It wasn't just patients who had received lots of blood transfusions.
DR. SEJVAR: Yes. Thank you for that.
CHAIRPERSON PRIOLA: Dr. Nelson.
DR. NELSON: Yes. There was one U.S. case of variant CJD that was apparently acquired in the U.K. How was that case detected?
DR. SEJVAR: That case actually was detected by a diagnosis in the U.K. This patient sort of had frequent back-and-forth travel between the United States and the United Kingdom and was pathologically diagnosed in the U.K.
CHAIRPERSON PRIOLA: Okay. Thank you, Dr. Sejvar.
Our next speaker is Dr. Steve Anderson.
DR. ANDERSON: Good morning. My name is Steve Anderson. I'm in the Office of Biostatistics and Epidemiology at the Center for Biologics Evaluation and Research, part of the FDA.
Actually, the goal of my talk is a comparison. So I'm going to take some of the prior information that you heard in Dr. Will's talk and some of the prior information that we've heard in Dr. Sejvar's talk and try to compare some of that information and then share with you some of the conclusions or lack thereof that we can draw from some of this information.
I'm a risk assessment person. I'm a data analyst. I'm not an epidemiologist. I'm not in surveillance, but I rely a lot in my work on quantitative analysis and assessing risk.
So just to start off comparing CJD and variant CJD, the risk of transfusion via blood, I think Dr. Will alluded to and the subsequent speakers in the next session are going to be talking about transmission of TSEs via blood transfusion in the animal experiments. I think the implications in the human system are, first of all, for CJD, the protein is not found in the lymphoreticular system or it has not been identified at this point, but for variant CJD there is some evidence that suggests it is found in the lymphoreticular systems.
And it, I think, is somewhat thought that there might be a higher possibility for or probability of transmission of variant CJD via blood products versus CJD.
Now, I'm basically just going to summarize this information because Dr. Will has given us excellent information about this case. The December 17th announcement in the U.K. of this case, the transfusion transmission, the recipient received red blood cells. I'm just going to skip through this onto our next slide.
And I apologize because there were too many different blood services and organizations to put on this slide. He had about 15 listed, and I ran out of space. So I apologize to any of those involved, but the study in the U.K. involved a large group of agencies that followed the donations, as he said, from 15 donors that were later diagnosed with variant CJD.
The critical thing when I look at this is it follows 48 individuals that receive blood products from these 15 donors, and as Dr. Will alluded to, there were a variety of different products, whole blood, RBCs, plasma, et cetera.
And he also alluded to this information as well, and actually it was -- I stand corrected. He said 20 units of plasma. So there were 18 units or 20 units in this case of plasma from variant CJD-infected donors included in fractionated products prior to 1998. I look at this and see that is a potential exposure route.
Again, thousand of potential exposures. I think the critical thing to remember here, though, is that you've got large batches of product being made, large dilution going on. So this would probably be a relatively low-risk pathway of exposure to variant CJD if the agent is, indeed, transmitted through the blood or blood products.
And I think it's important to emphasize, as he said, that so far variant CJD hasn't been observed to date for these products.
I'm not going to go much through this. Again, CJD, I'm going to move from variant CJD into CJD, talk a little bit about more on the side of CJD. It's a rare disease, again, that occurs in older individuals, long incubation periods.
I think the point that Dr. Sejvar made is that it's considered a low risk, CJD transmission via transfusion, considered a low risk, and I think from my standpoint if the risk was significant you might expect to see increases in the CJD rate annually. And as Dr. Sejvar said, at least in the United States the rate has remained stable for the last 20 or so years, and in many countries that are conducting surveillance that's also true.
I'm not going to go much through this study because Dr. Sejvar has already walked us through this study, the American Red Cross-CDC-NBDRC look-back study. I think the important thing here, I'm just going to emphasize the numbers since I'm more interested on the quantitative side.
Three hundred thirty recipients were followed, and for my analysis, I'm interested in these 116 recipients that lived longer than five years.
Again, there were no observed CJD infections that have been observed to date in this study.
So the next slide.
Again, Dr. Sejvar alluded to seven studies. I present one paper that evaluated five case control studies in 2,400 CJD patients. Again, there was no observed association between CJD and transfusion.
Again, these came from a variety of locations, Japan, U.K., Europe, and Australia. Again, I'm just going to move forward to the next slide.
He also alluded to this, although I presented it slightly differently. Basically, CJD studies in hemophilia populations. These you might expect to be at high risk since they receive frequent and perhaps significant amounts of blood products over a several year period.
So CDC has done autopsy studies and antemortem studies, first starting with 30, and I think that as Dr. Sejvar said, that has been expanded to 40.
Looking at patients who died of CNS symptoms after 1983, again, looking at those, there was no indication of CJD. They also looked at the more than 12,000 hemophilia patients assessed for CJD, again, and didn't find indications of the disease.
So in this high-risk population you don't see any indication of transmission transfusion.
And a similar study in the U.K., although they just did an antemortem study of -- postmortem study of 33 hemophilia patients. They had received concentrates over this period of time from '62 to 1995 from a range of 3 to 27 years.
Again, this was also an evaluated for variant CJD, I believe, and CJD, and no indication in this population of these diseases.
The next slide.
Okay. So that brings us to the evaluation I did, and it was a very simple analysis, given the information that is available. I'm going to walk you through an example comparison between the data for variant CJD and CJD, and it's nothing extremely complex because the data really aren't there yet, and I think one of our recommendations will be that further data are obviously needed.
Again, we looked at 48 recipients, the 48 recipients in the U.K. study for variant CJD transfusion infection. Of those 48, we really focused on these patients that had survived greater than five years post transfusion, and the one presumptive variant CJD infection that came six and a half years approximately after transfusion.
And then there is the data that Dr. Sejvar presented from the NBDRC CJD look-back study. Again, the interesting thing for us to focus on is these 116 recipients that survived greater than five years. Again, zero infections to date from those individuals, and let me just -- the next slide. I think I'm going to pass. Next slide.
Okay. So we compared those two groups, the 15 out of 48. We looked at those recipients, the percentage of recipients in those overall relatively small groups and the percentage surviving longer than five years post transfusion in the two groups, and they looked very similar.
So what we can say from this -- I did this because we're looking at U.K. populations versus the U.S. populations, and we wanted to be sure there wasn't any distinctions at this level of survival at the five-year point. Pretty much very similar, 31 percent, 32 percent, 35 percent for the CJD study. So very similar on that level.
And on to the next slide.
And the quantitative and analyst person in me wanted to set this up as a two-by-two table and see what I could glean from this information. I would say, you can do statistical analyses on these, and I played around with doing that, and basically the thing that just jumps out at you is zero and one. So that's why I sort of wanted to present this.
And what you've got from this basically, given the relatively small size of each group, it's really difficult to say much about these two groups. You've got zero and one, and the conclusion that you can draw from this is this could be a chance event. This could be due to a confounding factor. It could be due to transfusion, and I don't think we should eliminate the possibility that it's due to transfusion. But just based on the statistical analysis side of things, you can't really determine that just based on the size of the groups in this analysis.
I think it's important to say though that we're treating it as a presumptive case and acting as if it is, indeed, a transfusion-transmitted case to err on the side of caution.
And I think the one strong conclusion that I can draw from this information is that we really need additional data and research in this area to really determine what the trend is in this situation. You certainly would like to see a greater number of individuals enrolled in these studies to look at possible trends.
And the next slide.
There are certain challenges to doing that though. First of all, the size of the group so far has been small. The incubation period for these diseases is long. So if you are transfused with blood from an individual that was diagnosed with one of these TSE diseases, it will take a very long time, perhaps four years, five years, or longer, to actually develop disease.
And one thing we note is post-transfusion survival. Many of the patients that receive transfusions are very sick or have severe medical conditions. And many of them don't survive ? a significant percentage, let's say, don't survive beyond one or two years. So you've reduced your population that you can analyze significantly, and that's an important limitation in these studies, and I think I'll stop there.
CHAIRPERSON PRIOLA: Any questions for Dr. Anderson?
DR. BAILAR: I don't understand what I've been reading -- and now what you referred to very briefly -- about the possible benefits of dilution. I understand how the risk per person might go down, but it seems to me the total risk would go up.
DR. ANDERSON: You're correct. The benefits of dilution as far as -- can you repeat that?
DR. BAILAR: Well, if you had a blood product with, say, ten infective units in it, and you give it all to one person, you'll have one case. If you give it to 50 people, you'll have ten cases, but the risk per person goes down to 20 percent.
DR. ANDERSON: You're just spreading that risk.
DR. BAILAR: You're spreading a larger risk.
Now, the way around that would be to find that there is some minimal infective dose such that you can dilute beyond that and a tiny bit of the prion isn't going to cause a problem. But I don't know that that has been established.
DR. ANDERSON: Right. I mean, I think dilution is an issue and pooling is something that we definitely grapple with, and we don't know what the infectious does for a human for these agents are, and definitely, I think the most valuable thing that's really difficult to generate is you need a good, at least from a risk assessment person, is you need a good dose-response curve, and that's just not available.
So making the predictions when you start diluting down, down, down is very difficult, and we don't know what the threshold is. If you go below a certain threshold or amount of infectivity, whether infectivity is even possible. So you are spreading that out among a significant number of people potentially.
DR. BAILAR: But that seems to me, on the basis of very little knowledge, something that could be studied in animal systems.
DR. ANDERSON: Well, I think the issue here ?- and maybe one of the TSE experts might want to comment on that ?- is the more and more you dilute down, I think the longer it takes to develop infection. So I think those studies would just have to go on for very long periods of time, and then I'm not sure that that's necessarily possible.
DR. BAILAR: This apparent change in incubation period with decreasing dose is another matter I have some trouble with as a statistician, but I don't think we need to talk about it here.
DR. ANDERSON: Well, maybe we can talk offline.
CHAIRPERSON PRIOLA: Dr. Linden.
DR. LINDEN: Okay. So you're trying to use a statistical approach to see if there's a difference between variant CJD and CJD based on one case versus no cases out of 14 noninfection cases and 116 noninfection cases, and you're saying that the n in the groups is too small, and I understand from a statistical standpoint you'd like to see the groups be larger.
I mean, I would argue from a clinical standpoint we don't want to see those groups be any larger.
DR. ANDERSON: Well, from a public health perspective we don't want ?- you know, we want to see all groups at zero actually.
DR. LINDEN: Right. But from a statistical standpoint, if you continue to compare the one infection case and zero, I mean, we certainly hope it continues to be zero for CJD. Statistically, how many cases would you need to have in the noninfection groups to see a difference between one and zero? I mean, isn't that going to have to be a very large number for you to ever see a difference between one and zero statistically?
DR. ANDERSON: I didn't do those calculations, but you're correct. I mean, this is a low probability, very rare event, even for blood transfusion groups that we're evaluating, and we already narrowed things down. But I think it's such a rare event that, you know, you would need -- I don't know -- thousands, just off the top of my head, and that's obviously not realistic, given that you have to trace these people and then do the follow-up analysis with them.
CHAIRPERSON PRIOLA: Dr. DeArmond.
DR. DeARMOND: Just a comment. The dilution studies have been done in mice starting with high titer prions from brain, and you can define down to what a single infectious unit is, which I think includes like ten to the fifth prion protein molecules. So that has been done, but we have no concept about what it would be in blood. We don't even know if prion protein there is infectious yet, at least in the typical CJD, not variant CJD, but in typical CJD.
And actually Rohwer, Dr. Rohwer wanted to make a comment, and I'd like to hear what he has to say about that.
CHAIRPERSON PRIOLA: He's going to present data in a talk, so I thought we'd wait for that.
DR. NELSON: Yes. I think that this really isn't a statistical problem, as such. I think the biology of, you know, the proper incubation period and, you know, the fact that the cases were related with a proper incubation period makes it more persuasive.
But the one question I had was: Is the prion genotype the same, the distribution of the MM genotype the same in the U.S. and U.K. populations? In other words, is susceptibility the same in the two populations?
DR. ANDERSON: Oh, I have no idea on that.
CHAIRPERSON PRIOLA: Dr. Gambetti, do you want to? You were going to ask a question anyway.
DR. GAMBETTI: The question is: Is the susceptibility is the same?
DR. NELSON: Is the genotype distribution the same in the U.K. and the U.S.?
DR. GAMBETTI: No. Whether the homozygous methionines at codon 129 have the same risk of developing sporadic CJD in U.K. and in United States,. Is that the question?
DR. NELSON: The question is --
DR. GAMBETTI: And the answer is I don't know.
DR. NELSON: -- is is the distribution within the population of the MM genotype the same in the U.K. population and the U.S. population?
DR. GAMBETTI: Yes, yes. I based ?- the only elements to answer this question are the data from the National Prion Disease Surveillance Center and the one in the publication by Collins, the regional publication by Collins in which this risk was assessed, and, yes, it looks very comparable. That is definitely --
DR. NELSON: So about 35 percent of the population is MM genotype; is that correct?
DR. GAMBETTI: The population is 37, yes, MM, and we see -- I have the exact figure, but off of my head, I would say we see about 60, 70 percent of the case of prion -- no, actually higher, probably 75 percent of all the cases that we see of sporadic CJD are from patients that are MM.
DR. DeARMOND: I think the question had to do with proportions in England and here.
DR. NELSON: Yes.
DR. DeARMOND: And in the United States and North America, they're essentially the same as in Europe and in England. Japan is different.
DR. GAMBETTI: Yes, much more MM.
I just wanted to point out that actually it looks like the differences that are still conspicuous between variant CJD and sporadic CJD seem to kind of decrease, after a report from Switzerland, in which I'm sure you know, the scrapie prion protein was found in the spleen and muscle of about 20 to 30 percent of the cases with sporadic CJD, indicating that there must be, sometime during the course of the disease or during the entire course of the disease, some scrapie prion protein in the blood also of sporadic CJD patients, or at least a portion of sporadic CJD patients.
CHAIRPERSON PRIOLA: If there are no more questions for Dr. Anderson, I think we'll take our break a little bit early because it seems like a good place to break the two presentations, and we?ll reconvene at about quarter after.
(Whereupon, the foregoing matter went off the record at 9:57 p.m. and went back on the record at 10:16 a.m.)
DR. FREAS: Dr. Priola, I'd like to turn the meeting back over to you.
CHAIRPERSON PRIOLA: If all of the Committee members could come up and take their seats, in the second part of this morning's session we're going to hear from Dr. Robert Rohwer, who is going to discuss experimental transfusion models for TSEs.
DR. ROHWER: Thank you very much for having me here.
I'm going to be focusing today on the experimental work that has been done looking at the various issues associated with blood-borne TSE infectivity. I'll be mainly focusing on work from my laboratory because that's what I'm most familiar with, but I will be mentioning the work of others as we go along, and really the story is very consistent across laboratories as it stands right now.
If we could go to the first slide, to put this discussion in a proper perspective, it is important for you to understand how the experiments are actually done. There's hardly any infectivity in blood. As you'll see in a moment, it's about ten infectious doses per mL, which means that we cannot resort to the conventional method of endpoint dilution titration, which is typically used for assaying infectivity in the TSE agents.
In a typical brain experiment, we'd start with a very high titer of infectivity, and we'd go through a bunch of serial dilutions over here, and each dilution would be inoculated into a cage or more of animals, hamsters in this case. This is the 263K model that we'll be discussing here largely.
And then these animals would be allowed to incubate for approximately a year. And after a year, we did assess which animals became diseased and which didn't, and diseased animals are indicated in gray here, and you'd find an endpoint where you were no longer getting infections, where in fact there's less than one infectious dose per inoculum because some of these animals survive the infections.
And from that endpoint, using a couple of different statistical methods, you can calculate a titer. Nevertheless, you can kind of see what the titer is just by looking at the dilution. This isn't actually that big of an improvement on just the eyeball estimate.
But in the case of blood, the issue is that we're at this titer to begin with. The undiluted blood is already at what we call limiting dilution, a dilution where some animals become ill and some don't, and so what we devised early on was a strategy of instead of trying to do an experiment like this, we invest the animals entirely in the undiluted sample.
And then we get a spectrum of infections. Some get sick; some don't. And we can calculate the titer by the Poisson. I'll show you that in a minute.
But there is one other detail that I need to point out here, which is that there is a dose response associated with this infection. These animals that receive the highest dose come down in the hamster model in about 60 days. At the limiting dilution dose, they begin to get sick at about half a year and they continue to get sick from there on out for a year and a half.
And that's indicated here. This is a dose response. This is titer on this axis, logrithmically, and these are incubation times down here, and what you see is you get a fairly broad spectrum of response, but nevertheless, when you put it together it's a consistent dose response where the incubation takes longer the lower you go.
But once you get down to limiting dilution, the whole dose response goes away and you get random infections all the way out here for a year and a half.
We have a theory about why that happens, but we can discuss that later if you're interested.
So the model we've developed for these low titer inoculations is to create a donor animal, and at some time later collect the blood by exsanguination, process the blood or not, as we see fit, to make the various measurements we want to do, and then we want to look at a statistically valid sample of that blood, and we've standardized on a five mL whole blood equivalent for inoculation into hamsters.
The problem is to inoculate five mLs of blood by the intracerebral route into this small animal requires a lot of hamsters because you can only inoculate about 50 microliters per animal by that route.
Why are we using that route? Because it's the most efficient route, and the question we're trying to answer is: Is there infectivity there or not? And how much infectivity is there?
This is a quantitative assay. It's not necessarily a relevant route of inoculation for the acquisition of the disease, but it is a way to make an accurate measurement.
At some time later, in this case a year and a half later, we have this spectrum of infected versus uninfected animals, and this is actual data from the leukoreduction experiment that I'm going to show you later in the talk.
So in this case, in our whole blood inoculation we had 44 out of 100 animals inoculated acquired the disease, and just roughly you can see what the titer would be. It would be 44 divided by five mLs, or about 8.8 infectious doses.
However, the infectivity presumably assorts randomly into these animals. So, in fact, some of these animals that were infected probably received two doses instead of one dose. Others received three, some four, at diminishing levels as it goes up, and this is described very accurately by the Poisson distribution, and you can apply a correction, a very precise correction to this value, which jogs this number up to about 12 infectious doses per mL.
Associated with this, presuming that we are getting random assortment into these animals, there is also a very precise statistic associated with this, and the standard deviation is plus or minus 3.4 in this case.
What this tells us is that we can detect less than twofold differences in titer by this method. This is a vastly more precise method of measuring titer in the TSE agents than has ever been used by any other method.
But it is essential to what we have been able to do.
Now, we have looked at several large blood pools, like the one I just showed you, over the last seven or eight years by this method, and this is the range of titers that we've seen looking at pooled blood, and we've also looked at individuals -- next -- the individual titers.
In this case we inoculate a full two mLs of blood obtained from the individuals, and the titers range like this. So they kind of reflect the same distribution.
There are a set of control experiments that we did involving splenectomies that I'm not going to discuss today, but those titers also fell right in this group. If we look at the mean and the median -- next; put them both on, next -- we end up with something that's right around ten infectious doses per mL, and that's what we take as our kind of benchmark titer for TSE infectivity in this rodent model.
Now, we've made these measurements also in the BSE-adapted mouse model, where we have had two measurements now from pools, one at about ten infectious doses and another one at about 20, and Larisa Cervenakova has made some measurements which also fall nicely in this range using her variant CJD mouse model.
One of the first things you want to know is where is the infectivity in blood. How does it distribute? This is a component separation that was done using the ultracentrifugal methods protocol that's used by the American Red Cross. This was done on 250 mLs of pooled hamster blood, and this is, again, inoculating a large cohort of animals with each one of these fractions, and that's where these numbers are derived from.
The distribution of infectivity in this case went this way: 25 percent in plasma, 35 percent here, 20 here. That doesn't add up to 100 percent. If you re-normalize to 100 percent, you'd get this distribution over here.
This is a very complex fraction. You have everything in it, white blood cells, platelets, plasma, et cetera. There is also white blood cells and plasma contaminating this fraction. This is the cleanest fraction which contains pretty much plasma and some platelet fragments.
We were surprised to see this. Paul Brown and I, in an original experiment that we did years ago, saw this in the mouse Fukuoka strain. We weren't expecting it. We were thinking that it would be -- that everything would be associated with the white blood cells. That's clearly not the case. We have lots of evidence now that we've seen this over and over again now. This is a real effect though. We do not know what the nature of the infectivity is in this plasma fraction.
This is just a vastly more precise measurement of the same thing.
Because platelets could be responsible for that plasma contamination, we are very interested in knowing whether platelets themselves harbor the infectivity. Platelets in humans at least have quite a lot of the prion protein in them or on them, and that association implied that perhaps platelets could be involved in the blood-borne infectivity story.
I'd like to remind you, however, that the prion protein, the normal form of the prion protein is very widely distributed in the body. It is found, for example, in the heart at almost the same concentration that it's found in the brain, and yet we find very, very little infectivity in the heart.
So the correlation with infectivity is not with the prion protein itself. It's with the abnormal form of the prion protein, and the form that we find in platelets is the normal form, and what we see here is that in 22 mLs of blood which titered out, again, right on the money at ten infectious doses per mL in this case. Inoculating half of the entire Ficoll-purified platelet fraction, we had one infection that worked back to a titer of about 3.5.
Our feeling is that the platelets are not where the infectivity is in blood. However, I do want to make one warning about this. These were highly purified platelets. We did this in collaboration with platelet experts at the FDA. They were Ficoll-purified, washed exhaustively, et cetera, and as a consequence they do not represent what you would get in a platelet concentrate, which is a mixture of platelets, plasma and other components.
This does not say that platelets themselves or a platelet concentrate would have no infectivity in it.
We're also interested in where the infectivity might be in plasma, and the plasma industry was interested as well. With sponsorship from the Red Cross for this experiment, we did a Cohn fractionation using endogenously infected blood on 50 mLs of plasma from that component separation that I showed you a few minutes ago.
This is just showing you the volume distribution of the various fractions that come out of the plasma in the course of fractionation. And what we did here is we inoculated as much of these pellets as we could or often the entire thing, or if that was not possible, we inoculated at least a five mL whole blood equivalent so that we could relate it back to whole blood.
This data is plotted in the following way. This is incubation time down here on this axis, and these are the various fractions we looked at, and each dot represents an animal that acquired the disease at that point in time, the incubation time, and basically what I wanted to show you here is these are the whole blood samples here. In yellow are the various plasma fractions, and these are the various pellets of various sorts.
A point I want to make is that even though the concentration is low in the plasma fractions, the volume is high and the total amount of infectivity associated with the plasma frequently is similar to that that's found in these pellets where we are inoculating the entire pellets.
The main point I want to make here is that we were able to track the infectivity through the cone fractionation all the way to fraction IV but no further. We found nothing in fraction V or fraction V supernatant or in fraction II or fraction II supernatant.
This is the cone fractionation. We don't have time to go through this, but this is showing both arms going to the immunoglobulins over here and albumin over here. We saw infectivity to this point, but not beyond in this fractionation.
Another thing that we're all very interested in is when, in fact, does the infectivity appear in blood during the infection. This is something that can be addressed directly in the experimental models, and this is an experiment in which we inoculated a large cohort of animals in this particular case using the intracerebral route, but inoculating a low dose. So the incubation time was quite long by this route, somewhere between ten and 50 infectious doses.
And then at three week intervals we sacrificed pools of 20 animals, exsanguinated them, pooled all of the blood from that because what I wanted to get at here was what is the average behavior during the course of the infection, and then we would inoculate 100 animals. In this case 85 to 95 hamsters were inoculated with whole blood directly to measure how much infectivity was present at that point in the infection.
And we can see that three weeks after inoculation we saw nothing, saw nothing here. This was very reassuring to us because it answered a long question that we had about a possible artifact that could be associated with that, and that is that we were actually reisolating inoculum in the case of these blood experiments.
Since we saw none at these early times that rules that possibility out. This is also a very good control for us because we had a lot of animals invested at this point in time. We saw no infections, which tells us that our environmental controls are extremely good. We're not picking this up in our colony adventitiously.
And then the data are also very consistent. Midway through the clinical disease, we start seeing infections. We see more as the disease progresses with the highest titers at the time of clinical disease at 125 days. This is plotted in a graph in the next slide, and again, we see these two points with nothing in them, and then we see these very interesting kinetics.
What I can tell you is that we have another experiment on at the moment that's about a year out in its incubation where we inoculated the animals by the oral route. This is a much more natural route of infection, we believe, and we're seeing, to the extent that we can talk about it at this time, we're seeing what looks to be a very, very similar picture.
There is something very peculiar about this data which we don't understand, and that is that this is a linear axis over here. These are infectious doses per mL in blood, and my original assumption was that the blood-borne infectivity was probably coming from the brain. We have huge amounts of infectivity in the brain, and the clinical stage of this animal, ten to the tenth infectious doses per gram, and I could imagine that at a very low level it was spilling over into the bloodstream just due to the necrosis that was taking place in the brain.
But if that were true, we would expect the same kind of exponential growth kinetics that we see in the brain in the blood, and we're not seeing that here. This is absolutely linear, and it suggests that there is some other source for the blood-borne infectivity, and we're very curious to know what that is.
Of course, it's also of interest to know whether this disease can be transmitted even though there's infectivity in the blood. Let's put it that way. It wasn't clear to me when we began these experiments that it would be transmissible by the blood route. My own prejudice was that this stuff was probably associated with white blood cells, and it was on a dead-end pathway to elimination.
And these are central nervous system diseases. They're not hematogenous diseases, in the usual sense of that word, like HIV or HCV or something like that. And so it wasn't clear to me that if you actually transfused this blood that you'd actually also transmit the infection.
So we set up a transfusion model which is rather extreme in some ways. What we did is we took our donor and would exsanguinate them in clinical disease, and then transfuse the blood, which we expect to have about ten infectious doses per mL in it. We transfused two mLs of that to a recipient hamster. We would do a cannulation of the carotid, remove two mLs and then replace it with two mLs of this donor blood.
So essentially we're moving the clinical infection from an infected animal to an uninfected animal via the bloodstream at about a third of the blood volume of the animal. This is, on the basis of blood volume, this is a massive transfusion.
These are difficult to do, and over the course of four or five years we did about 100 of them, which are summarized here in this figure.
Early on, we had a transfusion transmission, but we only had one. We had the same problem that has occurred with the variant CJD transmission. What kind of statistic can you attach to that? Is that one in a million or what?
And that has encouraged us to go on and do additional transfusions. At the end of this study, this is where it stands at this point. We've seen three transfusion transmissions, but when we look back to see what we've done, we have over this period of time transfused a total of over 200 mLs of hamster blood by the transfusion route two mLs per hamster.
Well, if this had been brain-derived infectivity at somewhere between four to 20 infectious doses per mL, we would have had these kinds of titers in this 200 mLs, this amount of infectivity total. Even at a tenfold reduction in efficiency, which is probably more than is warranted for blood ?- it's less than brain, but it's actually quite an efficient route of transmission. It's quite an efficient route of transmission of brain- derived infectivity -- we still would have had 80 to 400 infectious doses. We should have seen most of these animals infected as opposed to what we actually saw.
So there is something different about the transfusion route of transmission compared to the IC route and compared to the introduction of brain-derived infectivity by the IV route.
On the other hand, had we been able to put the entire 200 mL volume into a single hamster, sort of the question that came up earlier from Dr. Bailar, we would have expected an infection for sure because an infectious dose is, by definition, the amount needed to cause an infection, and we had three of them.
What can we take from this? Well, it doesn't seem to us that blood plays a very important role in the pathogenesis of the disease in the hamster. We know that transient exposures to blood-borne infectivity in the right context by this transfusion route, at the highest titers that can be achieved naturally in blood, i.e., during clinical disease, did not transmit the disease efficiently. On a per animal basis, it was rare.
At earlier stages the titer would be even lower and the transmission would be even less efficient. So if blood-borne infectivity does play a role in the pathogenesis, it has to be because of chronic exposure to the very low, early preclinical levels of infectivity.
Nevertheless, it still may be a problem, a public health problem if, by transfusing large volumes, you can actually transmit the disease.
And this data contrasts sharply with the experience that has been obtained with sheep. Nora Hunter and Fiona Houston and their colleagues at the Institute for Animal Health in Great Britain or Scotland have done a number of sheep transfusions now where they have successfully transfused from experimentally infected sheep, experimentally infected with BSE, bovine spongiform encephalopathy, and from sheep that are naturally infected with sheep scrapie, showing that either by an experimental route or natural infection they can get these transmissions.
They're seeing them at a fairly high frequency in this flock, a higher frequency than we saw in the hamster model, but the model differs in some important ways from the one we're using. They're only transfusing four to six percent of the blood volume, even though they're transfusing large volumes, and they're seeing frequent transmissions.
By comparison, we were transfusing 33 percent of the blood volume, but at a low volume and rare transmissions. What this is telling me is that it's the total amount of infectivity that's transfused that's important. It has nothing to do with blood volume.
Okay. I'm going to discuss now an experiment that we've done and just very recently completed and are preparing at the moment for publication, and this is an evaluation of leukoreduction using this same endogenously infected blood model.
When the first variant CJD cases emerged in Great Britain, there was immediate concern for the blood supply, and that's because there did seem to be more peripheral involvement in this disease, and a likely source of that peripheral involvement was some sort of hematogenous spread of the infectivity, and so measures were taken to mitigate the risks from this.
One, the British stopped fractionating their own domestic plasma, but the other measure that was take is leukoreduction, and there were good reasons for doing this. A lot of laboratories besides our own had identified buffy coat as a source of infectivity in blood. And PrP scrapie and infectivity had been demonstrated in the lymphoid tissues of the variant CJD cases and in some other TSE infections as well.
And then at almost this same time, Aguzzi had published a paper showing that B lymphocytes, using knockout transgenic mice deficient in B lymphocytes, he showed that they were absolutely required for the propagation of the infectivity from peripheral sites.
Now, it was presumed that that was because B lymphocytes might either be replicating or transporting the infectivity. It has since been shown that their role is an indirect one. They are absolutely required, but indirectly, and so this isn't necessarily a relevant reason anymore, but it's part of the reasoning that went into the measure.
Once this was implemented, we knew about our component separation and had presented that several times and were concerned that leukoreduction might not be able to do the job because we only saw about half of the infectivity in the buffy coat.
Some other groups, Paul Brown and Larisa Cervenakova and their colleagues, and a group at the Scottish National Blood Transfusion Service did some direct experiments on leukoreduction. This experiment involved endogenous infectivity and a filter, a scaled down filter supplied by Paul, which showed no removal from plasma.
These people used brain-derived infectivity to spike all of the major manufacturers of leukoreduction filters and so no loss of infectivity by passage through any of these filters.
We decided that if we were going to contribute to this that we needed to do a different type experiment. We would use endogenous blood-borne infectivity. We didn't want to scale down because there would always be issues about the relevance of the scaledown, which meant using a full unit of blood, the commercial filters at their rated capacity, and we had a partner in this experiment in the Canadians.
Health Canada was proposing to also implement a universal leukoreduction, and they wanted to know whether this would have any effect on their risks to CJD. So they supported us financially, and we used their protocols and equipment to do the experiment and their personnel.
We ended up testing two Pall filters, next, which you'll see in the next, and logistically this is a difficult experiment. We had to get a large cohort of animals at the same stage of disease on the same day, collect the blood within a few hours, get it into a blood bag, do the leukoreduction, take our samples, and get it into animals, and get the infections underway.
We had everyone in the lab involved, plus a number of people from Health Canada, and it was a big party actually. But it was very nicely orchestrated by Luisa Gregori in my lab, and we were able to do this.
We were interested in meeting the AABB specifications for leukoreduction. We did a bunch of prototype experiments with normal blood to make sure that we could do this. We were within specs on everything except platelets, where our platelet recoveries were a little low.
And that's because the platelets enhancers are somewhat more dense than they are in humans and a larger fraction of them ends up with the red blood cell fraction.
So we collected this within two to four hours, did the whole experiment.
The first experiment we did was with this whole blood filter right here, the WBF2. We titered an aliquot of whole blood, an aliquot of the leukoreduced blood.
We then subsequently carried this through a hard spin to produce an RBC concentrate and platelet-poor plasma. We have these thing stored.
A few days later, the rest of the cohort was at a stage where we could bleed it, and so we collected another unit of whole blood and tested this plasma filter and RC filter right here.
We did not titer these. We did not have the funds to do that, but what we did do is determine that the blood behaved and met the AABB standards in this model, showing that this is an excellent model for doing this type of experiment.
They operated within specifications both with respect to white blood cell removal and red blood cell and plasma recoveries. Platelets were low.
This is the actual data. These are the recoveries over here, and these are the AABB specifications down here, and as you can see, we're right on for all of these things.
This was the second set of experiments and, again, a similar story.
This is the titration data. The prefiltration whole blood came out to about 12 infectious doses per mL; post filtration, about six. This is actually a little higher now because we've completed the Western blots on this data, and we found a couple more infections in the post-filtration group.
But what it's telling us is that we're only removing about 50 to 60 or 40 to 50 percent of the infectivity by leukoreduction.
Interestingly enough, this is exactly consistent with what we found earlier in our component separation by ultracentrifugation. Again, we saw about 45 percent of the infectivity in the white blood cell fraction and the rest in plasma and red blood cells.
So both of these experiments are highly consistent, and these are two completely independent measurements.
What would this mean for a unit of blood? Well, in this particular unit, we would have had 5,500 IC infectious doses in the in-going blood, by IV route at ten percent efficiency maybe 550, and the red blood cell component, this is our estimate. We would have had about 138.
Post filtration, we dropped both of these things by a little less than a half, but we still end up with significant amounts of infectivity in those fractions.
The implications here are leukoreduction is necessary, but not sufficient to eliminate the risk. Whatever measures we do take, I think, to get rid of the infectivity in these components, leukoreduction will have to be part of that solution.778
The infectivity in leukoreduced blood is in a different state. It appears to be in a more soluble state, and as a consequence, it may be harder to get rid of; may or may not, depending on the technology that's used.
And we haven't titered the post-filtration components. We'd like to do that just to see, you know, how it distributes farther down the line.
So in summary for the entire presentation here, from the animal models of blood-borne infectivity, I think we can say that we've had unequivocal demonstrations of blood-borne infectivity in rodents, sheep, and possibly now in monkeys. We've had diverse strains of agent that have been looked at, and this effect has been seen with familial Creutzfeldt-Jakob disease, the Fukuoka strain, variant CJD ?- this is Larisa Cervenakova's work ?- BSE, our work, and scrapie.
We've seen it in natural TSE infections, as well as experimental infections, and this is the Institute for Animal Health work with the sheep transfusions.
We've seen unequivocal demonstrations of transfusion transmission in hamsters. Larisa has seen some of these transmissions in her mouse system; and in sheep; diverse strains of agent, again; and in natural infections.
Moreover, there's a credible explanation for the difference in susceptibility to transfusion transmission that we saw between the hamster and the sheep.
So what we get down to is that all of the experimental data are consistent with and predictive of transfusion transmissions of TSE diseases in humans.
So in some ways we shouldn't have been surprised to see this though I, frankly, have to tell you I was surprised. It was quite a shock to hear this had happened just before Christmas.
But this is the time line. Bob Will has already gone over this, but I just want to reiterate it. This donation occurred three years before the donor died. This is preclinical. This is consistent with what we see in the hamster. We see infectivity, preclinically, halfway through the incubation period of the disease and beyond.
That's not to say it's not there earlier. It just means it's at titers lower than our assay is sensitive enough to pick up. My guess is it is probably there, but you'd have to inoculate 10 mLs or 50 mLs of blood in order to pick it up.
So it was a preclinical exposure, and we had a six-year incubation time, which is actually quite short compared to the incubation times that we typically see for iatrogenic cases due to dura mater or human growth hormone.
So if we take the presumption, and the FDA has just told us that they will presume that this was a transfusion transmission, then it fills in most of the missing gaps in this story. There can be TSE infectivity in human blood. It is present preclinically, and it is transmissible by transfusion. It may even have a virulence greater than might be expected from the incubation time in rodents, based on the incubation time in this particular case.
The only thing that's inconsistent with this story, and it is a major inconsistency, is why we haven't seen transfusion transmissions from classical cases of Creutzfeldt-Jakob disease. That has been discussed by a number of people already today. I can't really add much to that. Is it that we?re missing them, our surveillance isn't right? Is there something really truly different? We just don't know.
I just want to acknowledge the members of my lab that helped produce this data, in particular, Luisa Gregori and Claudia MacAuley ?- Claudia MacAuley is responsible for these surgeries that are involved in the transfusion experiments ? our collaborators at Health Canada, and Pall Corporation for the leukoreduction experiment.
Next? I think that's the end. Forget that. Go back. We're going to stop here.
CHAIRPERSON PRIOLA: Are there any questions for Dr. Rohwer from the Committee? Dr. Wolfe.
DR. WOLFE: Bob, now that it is clear or even clearer that cell-free plasma has some infectivity, have there been any efforts at filtering and things like that? I mean, we keep hearing about filters that will filter this stuff out. Have you looked at that or has anyone else looked at that?
DR. ROHWER: We have been working with nanofiltration, but we have not done nanofiltration on plasma.
DR. WOLFE: Are you planning to try that or is someone else?
DR. ROHWER: We've been working mostly with the Asahi people, and they are interested in that experiment, and I think getting it together logistically will be -- it's taken time, let?s put it that way. But it's something we're very interested in doing.
There are other ways you can get at this. We're very interested to know whether that infectivity is big or small. Also, there's always the possibility that it's there just because it's floating, and it's not being brought down by centrifugation, and there are ways we can get to that, at that directly by centrifugal methods, and those are more accessible to us, and we do have that underway, yes.
CHAIRPERSON PRIOLA: Dr. Hogan.
DR. HOGAN: Bob, thanks.
I'm very fascinated by the age issues with both variant CJD and sporadic CJD and the fact that the index case for blood transfusion was older. Is there any data either from your studies or others that age has anything to do with susceptibility relative to IV or IC inoculation, for that matter?
And it's also interesting that, of the 17 recipients in the U.K. that are still living, only three are younger than 40.
DR. ROHWER: Yes. That's hard information to generate in these rodent models because we need the whole lifetime of the animal to detect the infectivity. So, you know, if we started inoculating these animals in their adult, senior years, we don't have a hope in seeing it.
Personally, I think that's probably true for the human population as well. I don't personally feel particularly threatened by transfusion transmissions or any transmissions of TSEs, considering that it would take, you know, 20 years or more to develop.
So, yes, for technical reasons it's difficult. I would have to say in the sheep model most of that work has also been done with young animals, and you might have a little more flexibility there for getting at that question, but I don't think we're going to get it out of the rodent system.
CHAIRPERSON PRIOLA: Dr. Bracey.
DR. BRACEY: Yes. Thank you for the presentation.
Would you attribute any of the residual infectivity in the red cell component to that small amount of residual plasma that exists within the red cell? Could you speculate on that?
DR. ROHWER: Yes. We presume that all of the infectivity in the red blood cell concentrate is coming from plasma and residual white blood cell contamination. However, we have not proven that. Because of that, we put on an experiment I guess it was last May where we have tried to do the same thing we did for platelets. We've made a very highly purified preparation of red blood cells just to ask the question directly: Is there infectivity intrinsically associated with red blood cells?
I highly doubt it, but we haven't actually made the measurement. You know, another eight months or so from now we'll have an answer to that.
CHAIRPERSON PRIOLA: Dr. Khabbaz.
DR. KHABBAZ: Yes. First of all, thank you very much for a very elegant presentation of fascinating data.
I have two questions. One, in the experiments where you measured the preclinical infectivity you alluded to some experiments where you did oral inoculation and said it was the same pattern that you observed in terms of days-preclinical-to-clinical.
Is the absolute number of days the same or was it different?
The oral inoculation is very inefficient compared to the intracerebral inoculation. There's an interesting aspect of this. In the case of the intracerebral inoculation, we can reduce the titer down to ten to 50 infectious doses and get a reliable infection of the animals knowing that we introduced a very low titer.
To get the infection to go at all by the oral route, we have to infect with enormous amounts of infectivity. So we infected these animals with -- I forget. I think it's a milliliter of a ten percent brain homogenate, which means that they're getting approximately ten to the ninth infectious doses by the oral route.
We titered this material at the same time. We know that the efficiency of infection by that route looks like it's going to be about ten to the minus six compared to brain. So the actual measurable titer by that route is low. The incubation times are long. So the experiment is strung out for 150 days or something like that before we get to clinical disease going by that route.
But I just wanted to throw in that caveat. The actual exposure, in a way, is higher. So you kind of need both experiments to get a clean interpretation of the result. That was our feeling.
But in terms of percent of incubation time, they seem to be right on. About halfway through clinical disease, we're seeing infections. It just needs to go another, I think, four or five months before we can actually conclude the experiment and do the actual, you know, substantive quantitation of it.
DR. KHABBAZ: Thanks.
The other one, when you summarized the animal experiments, you mentioned the strains and I didn't see classic CJD there or did I?
DR. ROHWER: You didn't. The reason for it is we don't have a good animal model of it. It's not as readily transmissible to mice. Moira Bruce has some strains that she's trying to develop into a decent model. But it's a curious aspect of variant CJD, for example, that it's idiosyncratically relatively easy to transmit this disease to the R3 mouse and a couple of other readily available mice. It doesn't seem to transmit at all well to humanized transgenic mice. Exactly the opposite is true for sporadic cases, but we don't have those models in the laboratory, and so we haven't actually looked at those yet.
DR. KHABBAZ: Does that qualify the conclusion of transmissibility to all TSEs?
DR. ROHWER: Well, I tried to qualify that in my last slide. There is a big unanswered question here about why we don't see these things in sporadic Creutzfeldt-Jakob disease, and personally, I think that needs to be done, and we are developing the tools to do it actually. But it is an unanswered question at this time.
My own personal perspective on this is I'll be very, very surprised to see anything different in variant CJD, and part of the reason for that is that there's a very big difference between, for example, the hamster 263K model in the hamster and the variant CJD model in the mouse.
Hamster also has relatively limited peripheral involvement compared to some of the mouse models, and yet we don't see any difference between them in terms of their blood-borne infectivity.
CHAIRPERSON PRIOLA: Dr. DeArmond.
DR. DeARMOND: You made the comment that the increasing amount of titer in the blood was probably not related to release from the brain because it's an exponential increase in the brain and a linear increase in the blood.
But my feeling there is that a lot of the prion protein or the infectivity stays in the brain and that the mechanism of exit from the brain into the vascular system may be a linear system not related to the accumulation because a lot of it stays with cells or as amyloid-like deposits around the ventricular system.
DR. ROHWER: Well, there has to be an explanation, and I think we're going to have to invoke something like that, but in terms of just a direct relationship between the two sources of infectivity, there's a disconnect there, and so something like that is going to have to be invoked in order to explain this.
And that kind of thing is going to be difficult to access experimentally, I think, and our own approach to this was to do these splenectomy experiments that I alluded to earlier, and I'll just say something about that.
I was concerned that another potential artifact in the rodent model is extravasation of the blood when you handle these rodents, if they become alarmed at the time that you're bleeding them or something like that.
So we did a bunch of splenectomies, infected these animals by the oral route, the IC route, the IP route, and then we looked for blood-borne infectivity. And we didn't see any effect on the titers of blood-borne infectivity after splenectomy or by route or by any other of those parameters, which makes me feel like probably we're looking in the wrong place for the explanation.
CHAIRPERSON PRIOLA: Dr. Gambetti.
DR. ROHWER: Just a minute. Steve, it may well be that we have to go back to brain, you know.
DR. GAMBETTI: I may have missed something, but it is not clear to me how your model, which is extremely interesting, actually applies to the sporadic CJD simply because if I understood correctly, with the intracerebral inoculation, you essentially, by inoculating, disturb or destroy the blood-brain barrier. So you would expect that, at the time of the intracerebral inoculation, if you have a certain amount of PrPsc of the inoculum, that it will go in the general circulation, and therefore may start a very slow, general, systemic infection or PrPc along with the one much more rapid, much more florid in the brain.
If you do, of course, the intraoral administration and infection, you already are out from the sporadic CJD. At least, theoretically, you are not reproducing the sporadic CJD models.
So I wonder how you see this, how one could translate your data that are very interesting into the sporadic CJD that, of course, account for the largest number of cases.
DR. ROHWER: Well, we are very aware of that caveat associated with the work, and that's why fairly early on we started first going to low titer IC inoculations, because we didn't want to put very much infectivity in, and I actually have some very nice data showing how the infectivity is distributed after an IC inoculation, and a large proportion of it goes directly into the bloodstream and is transported systemically, as you say.
It's also the reason why we've moved towards this oral inoculation model, but it has also been rather reassuring to us that every time we've applied the oral model now, both in these splenectomy experiments and these incubation-time experiments, we're getting a consistent result. You know, it doesn't seem to have a big impact on the infection in the hamster at least.
But I agree with you. It's a practical matter in terms of using the oral inoculation because it's just inefficient, and it also makes me nervous applying this huge amount of infectivity to these animals. You have to care for them very carefully over the next month or so because they're shedding this stuff in their feces and everything else as well. So you have to do a lot of cage changes and you're relying on high- level dilution just to get it out of the environment. They have to be handled very carefully, and so it's a difficult model to work with.
On the other hand -- and it takes much longer for the infection to develop -- on the other hand, the benefit of eliminating these types of caveats is so strong that we are moving more and more to that model just for the reasons that you've mentioned.
On the other hand, I'm not convinced that there's really any real difference, you know.
DR. GAMBETTI: Just a point of clarification. You think it is possible, or is it possible that at the time of the inoculation you have a wave of PrPsc in the blood that may infect another organ and, therefore, there is an expansion of that PrPsc locally. So you have a fast-growing PrPsc formation in the brain, along with a very slow PrPsc formation systemically.
DR. ROHWER: Absolutely, and as far as I'm concerned, that's the explanation for the loss of the dose response at limiting dilution. In a limiting dilution case, you have a high probability that the infection will originate in some peripheral site instead of the brain because you're only inoculating one infectious dose.
So if that's the dose that ends up in your foot, the infection starts there. If it ends up in the brain, it starts in the brain.
But because you have a high preponderance of these peripheral sites dominating, suddenly you see a loss of incubation time, and what you're looking at actually are these very low-dose peripheral infections.
That's a hypothesis. We haven't proven that in any way whatsoever, but it seems to me like a very reasonable explanation for what's going on there. And it's well known. I mean, it has been known from ‑- there is some beautiful work in the '60s actually by Nims and Kearns (phonetic) looking at IC inoculation of rodents with respect to the development of the polio vaccine, where they show that the way it's typically done ends up with really an IC/IV inoculation where the vast proportion of the infection is IV, not IC.
And we've confirmed that actually with bacteriophages studies that I did, you know, 15 years ago or something like that. You can see it just instantly. It goes all over the place.
CHAIRPERSON PRIOLA: Dr. Petteway.
DR. PETTEWAY: Yes, thanks.
Just a comment, getting back to Dr. Wolfe's question concerning filtration or looking at filtration. A couple of weeks ago at the EMEA TSE workshop in London, there was quite a bit of data presented. A lot of labs are working on removal by filtration, including nanofiltration, and depending on the type of filter, depending on the process, it can be fairly efficient at removing PrPsc and infectivity, but it is a process- dependent issue.
CHAIRPERSON PRIOLA: Dr. DeArmond.
DR. DeARMOND: I'd like to follow up on my question and Pierluigi's because I think it's very important to identify the source of the infectivity in the blood, and certainly in our own experiments you inject into the brain, and the next day you see the spleen has a lot of infectivity in it. So we know that the inoculation does spread outside.
But in this case, one way to look at it is from your data with the presenting orally. Are the curves for the increase of infectivity titer in the blood -- do they occur in the same time point if you give it orally? That is ?- I can't remember. You start at about 60 ?- 51 days is where the breakpoint occurs and you start having your linear increase.
If you give it orally, do you get it at the same time point or is it delayed out to 100 or 150 days? Does it correspond to the then-exponential increase in the brain that results from oral, which should also be displaced in time?
DR. ROHWER: Well, I'm beginning to regret bringing this up because this is work in progress. So I don't want to be held to a definitive statement. We haven't seen the final results of this experiment.
But all I'm saying is that from the data that we've seen to date, we're seeing infectivity appear at the mid-clinical point. Realize that the infection is over. We've collected these pools. The pools are now incubating in animals, but the pools are also staggered because it took almost half a year for all of the infections to get to clinical disease in this model.
So the data is somewhat staggered, and we know what the incubation time was because the incubation time of the primary disease is over. We're waiting to see what the blood titers are.
As we look at those pools, we're seeing infectivity appear, mid-clinical disease just as it did before at very low titer, and then it looks like we're getting more cases down as we go up later in the infection, which is consistent with what we saw by the IC route, and that's by percentage of incubation time, not actual day values because the incubation time by the oral route is longer. It was 155 days or something like that.
DR. DeARMOND: So that would argue though -- so what you're saying is the blood titer looks like it's increasing at a later time from the oral route compared to the IC route. So that it's not --
DR. ROHWER: Yes.
DR. DeARMOND: So it is not congruent with the oral route or the IC route. It's displaced away from it.
DR. ROHWER: Yes. In absolute terms, that's true, yes.
DR. DeARMOND: And the only question then is --
DR. ROHWER: Yes. The interpretation would be if you shorten the incubation time, it will take -- whatever the incubation time happens to be -- it will take about halfway through for us to pick up the infectivity by these methods, and again, I emphasize that that's by these methods. That means we have to see at least one infection per five mLs of blood inoculated.
DR. DeARMOND: So the only question is what its timing is with the exponential increase that is occurring in the brain with the oral route.
DR. ROHWER: Right.
DR. DeARMOND: Whether it follows it or precedes it.
DR. ROHWER: And I have to say we don't have that data for the oral route.
CHAIRPERSON PRIOLA: Dr. Bracey.
DR. BRACEY: Currently, we are not universally leukocyte-reduced in the U.S. I don't know the exact figures, but it may be as many as 30, 40 percent of units are routine units.
Given the current state of information in your studies, I would present that you would make a recommendation for use of universal leukocyte reduction.
DR. ROHWER: I think that has to be modeled pretty carefully. It's not clear to me whether removing half the risk does anything.
CHAIRPERSON PRIOLA: Dr. Nelson.
DR. NELSON: Yes. I was very interested in your data on when, during the incubation period, you could identify infectivity. And it looked like for the hamsters it was about halfway through. I?m trying to correlate that with the tonsil data where there was one out of 8,000. I wonder if we could use, you know -- they are different data. Obviously, one is a bioassay and the other is demonstrating the prion protein in tissue.
But I wonder if we could use -- if we could merge those two data to predict the theoretical risk, you know, over time. I think the fact that you were able to show when infectivity occurred during the incubation period is pretty important and probably transferrable to the human case, but I wonder if you'd comment on that.
DR. ROHWER: It would be good to get Bob Will's comments on that as well, but my own perspective on this is the appendix results are just like the transfusion results. You know, one is not a good number to base a statistic on, and you can do it, and the prevalence rate that comes out of that number ranges from one in 8,000 to hundreds in 8,000 depending on how you interpret it.
What's really needed is another number, and so what needs to be done is to ramp up these surveillance programs so that you get the data you need to actually make a deduction.
There is something that has bothered me about the appendix result, however, and that is my guess is that the ascertainment rate for picking up variant CJD by this route is probably less than one, and if you look at it that way, it makes it even less reassuring.
And the ascertainment rate for picking up the transfusions, I suspect, is a lot better just because the program is in place for doing it.
But in terms of actually doing that kind of modeling, I hope that people like Steve Anderson and Cousins and people like that are doing that kind of modeling because I think it's important, yes.
I think Susie El-Saadany is here. She works on that kind of thing, as well.
CHAIRPERSON PRIOLA: Okay. I think we'll move on then to the next speaker. Thanks very much, Dr. Rohwer.
Our next speaker is one of the former chairmen of this Committee, Dr. Paul Brown.
DR. BROWN: Thank you, Chairman Priola. I feel a little bit like I'm coming home, maybe for the last time, but it's a nice feeling.
I was asked by David Asher to present the results of the study which several years ago was undertaken by us with the funding of the Baxter Pharmaceutical Company, and it has henceforth become known as the Baxter study.
Before I do that, assuming I have my full complement of 15 minutes and I'm not down to six and a half, I wanted just to make a comment or two about one or two of the interesting questions that have been raised in the course of the morning.
The difficulty of proving that sporadic CJD could be transfusion-linked I think is probably only going to be solved by exactly the reverse of the situation that is so compelling as evidence for variant CJD transmission; and that is, instead of having a young, typical variant CJD donating blood to a person who is elderly -- when I say "elderly,? that's my age -- you're going to have to have a classic sporadic elderly patient transmitting blood to an unusually young patient, and then you'll have the same kind of certainty which is not totally certain, but you'll have some confidence that that has happened. And that's not going to be easy to find.
I wanted also to say something about the 50 percent reduction of infectivity, whether or not that's worthwhile. The fact is we don't know obviously if it's worthwhile. My guess is that if I'm a recipient, anything is going to be worthwhile even if it hasn't proven to be worthwhile practically speaking. But a 50 percent reduction does reduce the risk by 50 percent, presumably, and that I mention in the context of this issue that came up in a very interesting way earlier in the morning about dilution.
Is there a point where you can dilute infectivity to the point of extinction? The question is not whether a dose that is measured by intracerebral inoculation is sufficient to transmit disease by some peripheral route like blood or orally. We already know that. That's a done deed.
Just to give you one example, BSE, for example, is 10,000 times less efficiently transmitted by the oral route than by direct IC inoculation. So by definition we know in terms of the route of infection that we can extinguish transmissibility.
The question is whether all things being equal and giving the infective material by a given route, shall we say, IC or IV, whether you can extinguish that by dilution, and that is a question that comes up time and time again. It's an experiment that actually I've been trying to do for some time, but nobody wants to do it, and yet it's an important question to answer, and it bear son the question as to whether or not a 50 percent reduction is enough to get below the threshold of transmissibility.
So that's an experiment that really cries out to be done, and I hope that someone will do it.
Now, it's always a mystery whether this technology is going to work or not. I use a Mac, and not only do I use a Mac. I use a Keynote program, which doesn't seamlessly transfer to anything.
DR. BROWN: I think we are probably going to be okay. The previous trial gave us a bilious green color for everything.
I was asked by David -- and with the kind permission of Corinne Lasmezas ? to also give you a summary of her studies, the studies of her group, directed by her now on what the French are up to with respect to primates.
But the first thing is our own study, and as I mentioned, it's a Baxter primate study, and those are the major participants. And the goal was twofold, and here is the first one: to see whether CJD, either sporadic or familial -- actually it turns out to be the familial CJD is incorrect. It really should be the Fukuoka strain of Gerstmann-Straussler-Scheinker disease. So it's really GSS instead of familial CJD ‑- when passaged through chimps into squirrel monkeys using purified blood components, very pure blood components.
So this addresses the question that was raised just recently about whether or not red cell infectivity that's been found in rodents is really in the red cells or is it contaminated.
We prepared these samples with exquisite care, and they are ultra-ultra-ultra purified. There's virtually no contamination of any of the components that we looked at ? platelets, red cells, plasma, white cells -- with any other component.
These are a sort of new set of slides, and what I've tried to do is make them less complicated and more clear, but I'm afraid I haven't included the build. So you'll just have to try and follow what I explain with this little red pointer.
There were three initial patients. Two of them had sporadic CJD. One of them had Gerstmann-Straussler-Scheinker syndrome. Brain tissue from each individual patient was inoculated intracerebrally into a pair of chimpanzees. All right?
From those chimps, either plasma or ultra purified -- in fact, everything is ultra-purified. I'll just talk about purified plasma, purified white cells -- were inoculated intracerebrally and intravenously to get the maximum amount of infective load into a pair of squirrel monkeys.
The same thing was done for each of these three sets. This monkey died from non-CJD causes at 34 months post inoculation.
Let me go back for a second. I didn't point out the fact that these were not sacrificed at this point. These chimpanzees were apheresed at 27 weeks when they were still asymptomatic. In this instance, we apheresed them terminally when they were symptomatic.
And before I forget, I want to mention just a little sidelight of this. Chimpanzees in our experience -- and I think we may be the only people that have ever inoculated chimpanzees, and that's no longer a possibility, so this was 20, 30 years ago -- the shortest incubation period of any chimpanzee that we have ever seen with direct intracerebral inoculation is 13 months.
So we chose 27 weeks, which is about seven months, and incidentally typically the incubation period is more like 16 or 18 months. The shortest was 13 months. We chose the 27th week, which is about six and a half months, thinking that this would be about halfway through the incubation period, which we wanted to check for the presence or absence of infectivity.
But within four weeks after the apheresis, which was conducted under general anesthesia for three or four hours apiece, every single one of the six chimpanzees became symptomatic. That is another experiment that I would love to conclude, perhaps because this is simply not heard of, and it very much smells like we triggered clinical illness. We didn't trigger the disease, but it certainly looks like we triggered symptomatic disease at a point that was much earlier than one would have possibly expected.
Maybe it will never be done because it would probably open the floodgates of litigation. There's no end of little things that you can find out from CJD patients after the fact. For example, the neighbor's dog comes over, barks at a patient, makes him fall down, and three weeks later he gets CJD. So you have a lawsuit against the neighbor.
I mean, this is not an unheard of matter, but I do think that physical stress in the form of anesthesia and four hours of whatever goes on with anesthesia, low blood pressure, sometimes a little hypoxemia looks like it's a bad thing.
So here we have the 31st week. All of the chimps are symptomatic, and here what we did was in order to make the most use of the fewest monkeys, which is always a problem in primate research, we took these same three patients and these six chimps. Only now we pooled these components; that is to say, we pooled the plasma from all six chimps. We pooled ultra-purified white cells from all six chimps because here we wanted to see whether or not we could distinguish a difference between intracerebral route of infection and intravenous route of infection.
With respect to platelets and red blood cells, we did not follow that. We inoculated both intracerebral and intravenously, as we had done earlier because nobody has any information on whether or not platelets and red cells are infectious, and so we wanted again to get the maximum.
This is an IV versus IC goal. This one, again, is just getting the maximum load in to see whether there is, in fact, any infectivity in pure platelets, in pure red cells.
And of all of the above, the only transmission of disease related to the inoculation was in a squirrel monkey that received pure leukocytes from the presymptomatic apheresis. So that goes some way to address the question as to whether or not it's a matter of contamination. To date the red cells have not been -- the monkeys that receive red cells have not been observed for more than a year because that was a later experiment.
So we still can't say about red cells, but we're about four and a half years down the road now, and we have a single transmission from purified leukocytes, nothing from plasma and nothing from platelets.
That was the first part of the experiment. The second part was undertaken with the cooperation of Bob Will and others supplying material to us. These were a couple of human, sporadic cases of CJD and three variant cases of CJD from which we obtained buffy coat and plasma separated in a normal way. That is, these are not purified components.
The two cases of sporadic CJD, the plasma was pooled from both patients. The buffy coat was pooled from both patients, and then inoculated intracerebrally and intravenously into three squirrel monkeys each. This is a non-CJD death five years after inoculation. The other animals are still alive.
For variant CJD we decided not to pool. It was more important to eliminate the possibility that there was just a little bit of infectivity in one patient that would have been diluted to extinction, if you like, by mixing them if it were to so occur with two patients, for example, who did not have infectivity. So each one of these was done individually, but the principle was the same: plasma and buffy coat for each patient was inoculated into either two or three squirrel monkeys. This is, again, a non-CJD related death.
In addition to that, we inoculated rain as a positive control from the two sporadic disease cases of human -- from the two human sporadic cases at ten to the minus one and ten to the minus three dilutions. We have done this many, many times in the past with other sporadic patients. So we knew what to expect, and we got exactly what we did expect, namely, after an incubation period not quite two years, all four monkeys developed disease at this dilution and at the minus three dilution, not a whole lot of difference between the two.
Now, these are the crucial monkeys because each one of these monkeys every three to four months was bled and the blood transfused into a new healthy monkey, but the same monkey all the time. So this monkey, for example, would have received in the course of 21 months about six different transfusions of blood from this monkey into this monkey, similarly with this pair, this pair, and this pair. So you can call these buddies. This is sort of the term that was used. These monkeys are still alive.
In the same way, the three human variant CJD specimens, brain, were inoculated into four monkeys, and again, each one of these monkeys has been repeatedly bled at three to four month intervals and that blood transfused into a squirrel monkey, the same one each time. Ideally we would love to have taken bleeding at three months and inoculated a monkey and then let him go, watch him, and then done the same thing at six months. It would have increased the number of monkeys eightfold and just unacceptably expensive. So we did the best we could.
That, again, is a non-CJD death, as is this.
This was of interest mainly to show that the titer of infectivity in brain from variant CJD is just about the same as it from sporadic. We didn't do a minus five and a minus seven in sporadic because we have an enormous experience already with sporadic disease in squirrel monkeys, and we know that this is exactly what happens. It disappears at about ten to the minus five. So the brain titer in monkeys receiving human vCJD is identical to the brain titer in monkeys that have been inoculated with sporadic CJD.
That's the experiment. All of the monkeys in aqua are still alive. They are approaching a five-year observation period, and I think the termination of this experiment will now need to be discussed very seriously in view of a probable six-year incubation period in the U.K. case. The original plan was to terminate the experiment after five years of observation with the understanding that ideally you would keep these animals for their entire life span, which is what we used to do when had unlimited space, money, and facilities. We can't do that anymore.
It's not cheap, but I think in view of the U.K. case, it will be very important to think very seriously about allowing at least these buddies and the buddies from the sporadic CJD to go on for several more years because although you might think that the U.K. case has made experimental work redundant, in point of fact, anything that bears on the risk of this disease in humans is worthwhile knowing, and one of the things we don't know is frequency of infection. We don't know whether this case in the U.K. is going to be unique and never happen again or whether all 13 or 14 patients have received blood components are ultimately going to die. Let's hope not.
The French primate study is primarily directed now by Corinne Lasmezas. As you know, the late Dominique Dromont was the original, originally initiated this work, and they have very active primate laboratory in France, and I'm only going to show two very simple slides to summarize what they did.
The first one is simply to show you the basis of their statement that the IV route of infection looks to be pretty efficient because we all know that the intracerebral route of infection is the most efficient, and if you look at this where they inoculated the same infective load either intracerebrally or intravenously, the incubation periods were not substantially different, which suggests but doesn't prove, but doesn't prove that the route of infection is pretty efficient.
Lower doses of brain material given IV did extend the incubation period and presumably it's because of the usual dose response phenomenon that you see in any infectious disease.
With a whopping dose of brain orally, the incubation period was even lower. Again, just one more example of inefficiency of the route of infection and the necessity to use more infective material to get transmissions.
And they also have blood inoculated IV which is on test, and the final slide or at least the penultimate slide shows you what they have on test and the time of observation, that taken human vCJD and like us inoculated buffy coat, they've also inoculated whole blood which we did not do.
So to a great extent their studies are complementary to ours and makes it all worthwhile.
We have about -- oh, I don't know -- a one to two-year lead time on the French, but they're still getting into pretty good observation periods. Here's three-plus years.
They have variant CJD adapted to the macaque. That is to say this one was passaged in macaque monkeys, the cynomolgus, and they did the same thing. Again, we're talking about a study here in which like ours there are no transmissions. I mean, we have that one transmission from leukocytes, and that's it.
Here is a BSE adapted to the macaque. Whole blood, and then they chose to inoculate leukodepleted whole blood, in both instances IV. Here they are out to five years without a transmission.
And then finally oral dosing of the macaque, which had been infected with -- which was infected with BSE, but a macaque passaged BSE, whole blood buffy coat and plasma, all by the IC route, and they're out to three years.
So with the single exception of the leukocyte transmission from our chimp that was inoculated with a sporadic case of CJD or -- excuse me -- with a GSS, Gerstmann-Straussler, in neither our study nor the French study, which are not yet completed have we yet seen a transmission.
And I will just close with a little cartoon that appeared in the Washington Post that I modified slightly lest you get too wound up with these questions of the risk from blood. This should be a "corrective."
DR. BROWN: Thanks.
CHAIRPERSON PRIOLA: Yes. Any questions for Dr. Brown? Dr. Linden.
DR. LINDEN: I just want to make sure I understand your study design correctly. When you mention the monkeys that have the IV and IC inoculations, the individual monkeys had both or --
DR. BROWN: Yes, yes, yes. That's exactly right.
DR. LINDEN: So an individual monkey had both of those as opposed to some monkeys had one and some had the other?
DR. BROWN: Correct, correct. Where IC and IV are put down together was IC plus IV into a given monkey.
DR. LINDEN: Into a given monkey. Okay.
And the IC inoculations, where were those given?
DR. BROWN: Right parietal cortex, Southern Alabama.
DR. BROWN: Oh, it can't be that clear. Yeah, here, Pierluigi.
CHAIRPERSON PRIOLA: Dr. Epstein.
DR. BROWN: Pierluigi always damns me with feint praise. He always says that's a very interesting study, but. I'm waiting for that, Pierluigi.
I think Jay Epstein --
DR. GAMBETTI: I will say that there's an interesting study and will say, but I just --
DR. GAMBETTI: -- I just point of review. You talk about a point of information. You say that ‑- you mention GSS, I guess, and the what, Fukuowa (phonetic) ‑-
DR. BROWN: Yes, Fukuoka 1.
DR. GAMBETTI: Fukuowa, and is that from the 102, if I remember correctly, of the --
DR. BROWN: Yes, that is correct.
DR. GAMBETTI: Because that is the only one that also --
DR. BROWN: No, it's not 102. It's 101. It's the standard. It's a classical GSS. Oh, excuse me. You're right. One, oh, two is classical GSS. It's been so long since I've done genetics. You're right.
DR. GAMBETTI: Because that is the only one I know, I think, that I can remember that has both the seven kv fragment that is characteristic of GSS, but also the PrPsc 2730. So in a sense, it can be stretching a little bit compared to the sporadic CJD.
DR. BROWN: Yeah, I think that's right. That's why I want to be sure that I made you aware on the very first slide that that was not accurate, that it truly was GSS.
There's a GSS strain that has been adapted to mice, and it's a hot strain, and therefore, it may not be translatable to sporadic disease, correct. All we can say for sure is that it is a human TSE, and it is not variant. I think that's about it.
DR. GAMBETTI: I agree, but this is also not perhaps the best --
DR. BROWN: No, it is not the best. We understand --
DR. GAMBETTI: -- of GSS either.
DR. BROWN: Yeah. If we had to do it over again, we'd look around for a -- well, I don't know. We'd probably do it the same way because we have two sporadics already on test they haven't transmitted, and so you can take your pick of what you want to pay attention to.
DR. EPSTEIN: Yes, Paul. Could you just comment? If I understood you correctly, when you did the pooled apheresis plasma from the six chimps when they were symptomatic at 31 weeks, you also put leukocytes into squirrel monkeys in that case separately IV and IC, but in that instance you have not seen an infection come down in squirrel monkey, and the question is whether it's puzzling that you got transmission from the 27-week asymptomatic sampling, whereas you did not see transmission from the 31-week sampling in symptomatic animals.
DR. BROWN: Yes, I think there are two or three possible explanations, and I don't know if any of them are important. The pre-symptomatic animal was almost symptomatic as it turned out so that we were pretty close to the period at which symptoms would being, and whether you can, you know, make much money on saying one was incubation period and the other was symptomatic in this particular case because both bleedings were so close together. That's one possibility.
The other possibility is we're dealing with a very irregular phenomenon and you're not surprised at all by surprises, so to speak so that a single animal, you could see it almost anywhere.
The third is that we, in fact, did just what I suggested we didn't want to do for the preclinical, namely, by pooling we got under the threshold. See?
You can again take that for what it's worth. It is a possible explanation, and again, until we know what the levels of infectivity are and whether by pooling we get under the threshold of transmission, we simply cannot make pronouncements.
CHAIRPERSON PRIOLA: Dr. DeArmond.
DR. DeARMOND: Yeah, it was very interesting data, but the --
DR. BROWN: I just love it. Go ahead.
DR. DeARMOND: Two comments. The first one was that the GSS cases, as I remember from reading your publications -- I think Gibbs was involved with them -- when you transmitted the GSS into animals, into monkeys, perhaps I think it was chimps, the transmission was more typical of CJD rather than GSS. There were no amyloid plaques. It was vacuolar degeneration so that you may be transmitting a peculiar form, as I criticized once in Bali and then you jumped all over me about.
DR. BROWN: I may do it again.
DR. DeARMOND: Calling me a bigot and some other few things like that.
DR. BROWN: Surely not. I wouldn't have said that.
DR. DeARMOND: So there could be something strange about that particular --
DR. BROWN: Yeah. I think you and Pierluigi are on the same page here. This may be an unusual strain from a number of points of view.
DR. DeARMOND: The other question though has to do with species barrier because the data you're showing is kind of very reassuring to us that it's hard to transmit from blood, but the data from the sheep and from the hamsters and some of the work, I think, that has been done by others, that it's easy in some other animals to transmit, hamster to hamster, mouse to mouse.
Could you comment on the --
DR. BROWN: That's exactly why we went to primates. That's exactly it, because a primate is closer to a human than a mouse is, and that's just common sense.
And so to try and get a little closer to the human situation and not totally depend on rodents for transferrable data, that is why you would use a primate. Otherwise you wouldn't use them. They're too expensive and they cause grief to animal care study people and protocol makers and the whole thing.
Primate studies are a real pain.
DR. DeARMOND: But right now it's inconclusive and you need more time on it.
DR. BROWN: I believe that's true. I think if we cut it off at six years you could still say it was inconclusive, and cutting it off at all will be to some degree inconclusive, and that's just the way it is.
DR. DeARMOND: So what has to be done? Who do you have to convince, or who do we all have to convince to keep that going?
DR. BROWN: Thomas?
Without trying to be flip at all, the people that would be the first people to try to convince would be the funders of the original study. If that fails, and it might for purely practical reasons of finance, then we will have to look elsewhere because I really don't want to see those animals sacrificed, not those eight buddies. Those are crucial animals, and they don't cost a whole lot to maintain. You can maintain eight -- well, they cost a lot from my point of view, but 15 to $20,000 a year would keep them going year after year.
CHAIRPERSON PRIOLA: Dr. Johnson.
DR. JOHNSON: Yeah, Paul, I'm intrigued as you are by the shortening of the incubation period. Have you in all of the other years of handling these animals when they were transfused, when they were flown out to Louisiana at night -- a lot of the stressful things have happened to some of these chimps. Have you ever noticed that before or is this a new observation?
DR. BROWN: Brand new.
MR. JOHNSON: Brand new. Okay.
CHAIRPERSON PRIOLA: Bob, did you want to say something? Dr. Rohwer.
DR. ROHWER: The Frederick fire, wasn't that correlated with a lot of --
DR. BROWN: Not that I k now of, but you may --
DR. ROHWER: Well, that occurred shortly after I came to NIH, and what I remember is that there were a whole bunch of conversions that occurred within the few months following the fire. That was fire that occurred adjacent to the NINDS facility, but in order to protect it, they moved the monkeys out onto the tarmac because they weren't sure it wouldn't burn as well.
DR. BROWN: Well, if you're right, then it's not brand new, but I mean, I'm not sure how we'll ever know because if I call Carlton and ask him, I'm not sure but what I would trust the answer that he gives me, short of records.
You know, Carlot is a very enthusiastic person, and he might say, "Oh, yeah, my God, the whole floor died within three days," but I would want to verify that.
On the other hand, it may be verifiable. There possibly are records that are still extant.
DR. ROHWER: Actually I thought I heard the story from you.
DR. BROWN: You didn't because it's brand new for me. I mean, either that or I'm on the way
CHAIRPERSON PRIOLA: Dr. Bracey.
DR. BRACEY: I was wondering if some of the variability in terms of the intravenous infection route may be related to intraspecies barriers, that is, the genetic differences, the way the cells, the white leukocytes are processed, whether or not microchimerism is established, et cetera.
DR. BROWN: I don't think that processing is at fault, but the question, the point that you raise is a very good one, and needless to say, we have material with which we can analyze genetically all of the animals, and should it turn out that we get, for example, -- I don't know -- a transmission in one variant monkey and no transmissions in another and a transmission in three sporadic monkeys, we will at that point genetically analyze every single animal that has been used in this study, but we wanted to wait until we could see what would be most useful to analyze.
but the material is there, and if need be, we'll do it.
CHAIRPERSON PRIOLA: Okay. Thank you very much, Dr. Brown.
I think we'll move on to the open public hearing section of the morning.
DR. FREAS: As part of the advisory committee process, we have open public hearings to allow members of the public to address the committees on any issues pending before the committee. There will be three such open public hearings at this meeting, two today and one tomorrow.
At this time I've received two requests to address the committee at this morning's meeting. These presentations will be limited to six minutes. The Chair has been required to read a statement regarding conflicts of interest at these open public hearings.
S, Prior Priola, would you read the public statement?
CHAIRPERSON PRIOLA: Both the Food and Drug Administration, FDA, and the public believe in a transparent process for information gathering and decision making. To insure such transparency at the open public hearing session of the Advisory Committee meeting, FDA believe that it is important to understand the context of an individual's presentation.
For this reason, FDA encourages you, the open public hearing speaker at the beginning or oral statement to advise the committee of any financial relationship that you may have with the sponsor, its production, and if known its direct competitors. For example, this financial information may include the sponsor's payment of your travel, lodging or other expenses in connection with your attendance at the meeting.
Likewise, FDA encourages you at the beginning of your statement to advise the committee if you do not have any such financial relationships. If you choose not to address this issue of financial relationships at the beginning of your statement it will not preclude you from speaking.
DR. FREAS: Thank you.
Our first speaker this morning is Dr. Michael Fitzpatrick. He's the Chief Policy Officer, America's Blood Centers.
DR. FITZPATRICK: Good morning. I want to thank you for the opportunity to speak, and as Bill said, I'm the Chief Policy Officer for America's Blood Centers, which represents 75 community based, independent collecting agencies in the U.S. and Hema-Quebec in Canada. So my salary is related to blood collection, and I think for disclosure that probably covers it.
We wanted to take this opportunity not to provide written comment, but just to remind the committee of a few things, and make a couple of comments on the morning.
One, that the impact of deferrals for vCJD can't be lessened. We lost eight to ten percent of our donors based on the precautionary principle and were able to compensate for that through recruiting efforts, but at best the inventory today in the U.S. is tenuous. We have a two to three-day supply of blood as opposed to at least a five-day supply of blood that we would like to be.
No one wants to sacrifice safety for supply, however. So we would ask that the committee take into consideration the safety of the patient, which of course is the paramount issue.
We don't have a way to measure the resiliency of the population at this point. How many more donors can we defer before we hit a recruitment plateau that we can't go beyond?
Dr. Epstein and other speakers have given you an excellent overview of the implications in sentinel populations of transfusion transmission of variant CJD, and those populations would be the hemophilia group, the sickle cell group, and the thalassemia group.
That dovetails very well with Dr. Brown's presentation, I believe, on his animal experiments. Those animals who received chronic transfusion and have not developed a disease would appear to mirror what's going on in the population. A single purported transmission in the U.K. is just that, a single purported transmission. At this point one positive is one positive, and it may or may not be positive. That patient was subject to the same living conditions as all the other individuals in the U.K. and could be a coincidental event, although statistically it looks unlikely, but we don't know that for sure because there isn't enough data.
So as you go through these considerations, we would ask that you consider first, of course, the safety of the patients, as we do. We would ask that you consider the data that you have seen and the data that you will see. Having been involved with this for a long time, I can only say that it appears we have more data. I'm not sure we have conclusive data yet.
The actions we have taken have resulted in no provable transmission, and we have yet to see a human case in the United States.
So I would ask that as you consider these things, that you consider all of those implications.
And can I ask Paul a question?
CHAIRPERSON PRIOLA: Sure, go ahead.
DR. FITZPATRICK: Dr. Brown. Did he leave?
CHAIRPERSON PRIOLA: Well, you could have. Dr. Brown, are you still in the room?
DR. FITZPATRICK: Oh, there he is.
CHAIRPERSON PRIOLA: Oh, there he is.
DR. FITZPATRICK: Paul, the animals that died of natural causes or on autopsy, were there any clinical sign of brain involvement at all?
DR. BROWN: They have not all yet been done, but those that have have no signs of infection.
DR. FREAS: Thank you very much.
Our next speaker this morning is Dr. Hatte Blejer. Forgive me if I'm mispronouncing your last name.
DR. BLEJER: Yeah, it's Blejer, Blejer or Blejer.
I represent myself. So I pay my own salary and I don't owe anybody anything.
I'm going to read my statement.
My husband died about a month ago of CJD. He was 52 years old, and he had numerous neurosurgeries in the late 1970s. Possibly he became infected at that time, possibly from a dura mater graft. He had shunt surgeries and revisions in the '70s in two states and a pineal tumor resection in Boston, Massachusetts. The CDC is investigating Daniel's case on their initiative.
I became concerned about the safety of blood products and medical devices when he was diagnosed in September of 2003. Daniel was B negative, and he donated blood three times a year for 25 years beginning in the 1970s.
I became more concerned in December of 2003 as he lay dying when I read of the suspected case of vCJD via blood transfusion.
Now, CDC has talked about the fact that they're getting these cases reported, and I want to give you some personal information. When I heard the diagnosis, which is supposedly 90 percent probable, I asked the hospital to contact various organizations, the Red Cross, the CDC, and the Virginia Department of Public Health. They told me I should report it. So I started trying to report it while driving 120 miles round trip to my dying husband's bedside.
So I did get the Red Cross. It took me four phone calls, and they were very helpful, and they contacted other organizations that have received blood or plasma from Daniel, and I believe there was a recall of albumin, I believe.
If I had not contacted the Red Cross, they would have never known that a frequent blood donor had CJD, and it's not optimal for the family member to be having to contact the public health officials.
Okay. My husband was in Maryland when he had a somewhat definitive diagnosis. That's not reportable in Maryland. He died in D.C. It's not reportable in D.C. Okay? But he's a resident of Virginia.
So more concerning to me actually than the blood is the neurosurgeries. I know that's not the topic, but because it's FDA and CBER and we're talking about biological devices, dura mater grafts, and we're talking about neurosurgical instruments, Daniel had seven neurosurgeries this year, in 2003, while his CJD was active, and the reason that was he had aqueductal stenosis.
So he had a shunt, and when he went into a coma in January of 2003, from the time he went into a coma they thought it was due to the shunt. When he didn't retain and his mental and gait status started deteriorating, they presumed that his shunt needed adjusting.
So various parts were replaced. It was internalized, externalized, in seven surgeries, and as far as I know, there's no indication that the surgical instruments were destroyed. So when you talk about that kind of a process, you ought to talk about at least being able to track surgical instruments so that when you have a case like my husband, you can get rid of those surgical instruments afterwards.
I did report Daniel's case myself to Virginia, to the Department of Health, Epidemiology. They did not contact me. CDC tells me they are aware, and again, he died in D.C. So Virginia is not aware that a Virginia resident has had CJD.
Anyway, in conclusion, his complex case illustrates that our public health system may endanger the public, and I realize that it does depend upon whether it's transmissible via blood products and medical devices, but since he might have been infected by a biological and medical device over two decades ago, when our knowledge and our safeguards were less than today, but when we suspected the cadaver material was not risk free, it is my hope that the U.S. government and the FDA are taking the utmost precautions in light of recent research and the recent possible case -- and I'm talking about the kind of animal models that we've heard about -- and the recent possible case of variant CJD transmitted via blood to safeguard against future infections.
It's a long incubation period. We have little numbers, and we don't know. So with deference to the blood supply issue, I know there's an issue, but we need to do everything we can because unless you have seen someone die over 12 months like I have, you don't know what the human impact is.
Okay. So one of the ideas I had was that people who have had neurosurgery. So you don't let people from Great Britain come in and donate if they've lived in Great Britain for more than six months, but someone who had neurosurgery in the '70s may, in fact, be higher risk. So that is one of the suggestions I have that's very concrete.
People don't know whether they got dura mater grafts. They have no idea. The doctor barely mentions it in the 1970s. The records are destroyed likely. So you have some high risk patients who are donating blood 70-plus times over 25 years, probably 35-plus times in the ten-year possible infectivity stage.
So that's all I have. Thanks for letting me talk.
DR. FREAS: Thank you very much.
I believe we have --
DR. FREAS: -- a couple of questions for you.
CHAIRPERSON PRIOLA: Dr. Wolfe.
DR. WOLFE: Thank you very much with the difficulty you must have had presenting what has happened to you.
You may know we have been attempting for five or six years to get the FDA to ban cadaveric dura mater from grafts. Britain banned it, Bob, 15 years ago, right?
DR. WILL: A long time ago.
DR. WOLFE: More than 15 years ago. Japan has banned it. Canada has banned it. It doesn't make any sense.
That does not steep backwards to the time when your husband may have gotten a graft, but certainly it does not make any sense knowing what we know now to allow in this country, unlike the other four mentioned ones, these grafts to occur.
You certainly raise a number of logistical questions about reporting and what happens where instead of having one National Health Service, as in Britain, we have a number of state sort of non-organized health services, and so what has happened to you is entirely predictable, unfortunately and sadly.
DR. BLEJER: I have heard it from 50 other families.
DR. FREAS: I'm sorry. We can't record you unless you're at a microphone, and we would like to record your --
DR. BLEJER: I wanted to just mention that I'm in contact with 50 to 100 families who have lost family members. So the things I said about frequent blood donation and about difficulty of reporting, I've heard this over and over again.
I mean, I had to fight to get a diagnosis. I had to drag my husband to about five different places, and that's in Washington, D.C. So think what it must be like out in the hinterlands.
CHAIRPERSON PRIOLA: Dr. Bailar.
DR. BAILAR: I find this story very disturbing. Is there anybody here who will defend the difficulty of getting this thing reported?
I'm not the one to look into it, but I think somebody really should. It may be a job for a tenacious investigative journalist or somebody, but somebody ought to be looking into this to find out what the problem is in getting a simple report in and fix that problem.
DR. GAMBETTI: May I?
CHAIRPERSON PRIOLA: Yes, Dr. Gambetti.
DR. GAMBETTI: What do you mean by "reporting," that it has been referred to, for example, the center like the National Prion Disease Pathology Surveillance Center? Is that what you mean by reporting?
DR. BAILAR: Well, that, plus the state authorities, plus the CDC.
DR. GAMBETTI: Yeah.
DR. BAILAR: These things, every one of them, should be widely known and widely investigated, and that did not happen
DR. GAMBETTI: I can tell you for the National Prion Disease Pathology Surveillance Center essentially probably 60, 70 percent of our time is spent in trying to get these cases referred to us, and it is extremely difficult. It is difficult because many institutions are reluctant to perform an autopsy on these cases.
So the center has to struggle to find other institutions around to have the autopsy performed for a fee. So there is constantly a search for other locations to do the autopsies. There is constantly trying to raise awareness in neurologists and pathologists to submit cases to us.
So it is really an uphill battle. It looks like we are making some inroads in the number of cases reported as compared to the number of cases expected. It is increasing. We are 50 percent about and now it looks like we are going up to maybe 60 percent, but still it is very difficult.
So this is the point of view of the surveillance center, but I don't know about other issues that you raised.
DR. BLEJER: Yes, Dr. Gambetti is right. I failed to mention that the hospital told me that there was no need for a biopsy or autopsy, and this is a regional teaching center in Baltimore.
I'm Jewish. I didn't want to have an autopsy on my husband, and I had an autopsy only because there are family members out there who through the E-mail told me that this was really, really important.
When you have a family member dying, you need those neurologists, neurosurgeons counselors to help you because this is a painful situation altogether. To have them tell you not to get an autopsy and then to actually have to figure out how to get the autopsy yourself is ridiculous.
CHAIRPERSON PRIOLA: Okay. For just one moment we'd like to make sure there's no one else who wants to speak at the open public hearing, and then we'll move on to the discussion.
DR. SCHOENBERGER: This was just to help answer some of the issues.
CHAIRPERSON PRIOLA: Okay. Dr. Gambetti and then Dr. Schoenberger if you want to.
DR. GAMBETTI: I really sympathize with your case because unfortunately I have heard similar stories over and over. I have a simple question. Was an autopsy finally performed in your late husband and was sent to the surveillance center or not?
DR. BLEJER: I directly contacted --
DR. FREAS: I'm sorry. You're going to have to come to a microphone. Otherwise we won't be able to put your word on the transcript.
DR. BLEJER: I personally contacted the National Prion Disease Pathology Surveillance Center on my own. I contacted the office manager because the family network of CJD families, CJD Voice, helped me come to that decision. So I arranged for the autopsy myself, and I had lots of help from your office manager, yes.
DR. GAMBETTI: So he eventually was examined. The case was sent.
DR. BLEJER: He only died recently. It's only about five weeks since he died at the age of 52, yes.
DR. GAMBETTI: It was sent. It was sent. That's my question.
DR. BLEJER: Yes, yes, yes. All the medical records, too.
CHAIRPERSON PRIOLA: Dr. Schoenberger, did you want to clarify something?
DR. SCHOENBERGER: No, I just wanted to mention that CDC is very much aware of this type of problem and is the basis for our, in fact, funding Dr. Gambetti's group to promote increased autopsies so that they can get these cases documented quickly.
We also have recently provided some funds to the CJD foundation and the president of that foundation is here today, Florence Kranitz, and they run a telephone hot line for families, and they can call and get guidance as to how to proceed when somebody in their family gets this disease, and they can do that in a very sensitive way and at the same time encourage such an autopsy to be done.
I think it's important for people who are making policy to understand that what Mr. Blejer has experienced is not totally uncommon, and I have found myself in meetings where people will get up and have said, "You know, there has never been a case transmitted by surgical instruments," and then the type of case that Mr. Blejer represents comes to my mind, and I'll say, "How can we know that for sure?"
I mean our data comes to us, and in fact, Mr. Bleger will come to us through many mechanisms. First, the doctor is going to put CJD on the death certificate. That makes it reportable in a sense to CJD, but as you pointed out, that will come later.
We also got a report from the American Red Cross on Mr. Blejer. We got a report from FDA on Mr. Bleger. That is probably due in part to many of the people that Ms. Blejer has contacted.
So we are getting these reports from multiple groups. The State of Virginia, the State of Texas, the State of Massachusetts have all gone to try to find records on this particular patient, and as Ms. Blejer indicated, they're having difficulty finding a lot of the records, although I can say that the operation, as I understand it, was done in Boston, removal of a pineal tumor, and that surgical records that you can get does not indicate that a dura mater was used at that instance.
Now, that's 1979. The death is relatively recent. Most of the dura mater cases indicate an incubation period that would be a little bit sooner than that. I think the longest on record is 23 years. So 24 years would be the longest ever. So it may well be that based on interval that the 1979 surgery was not really responsible for the illness in this case.
We've talked to the American Red Cross and have many of the blood donations that Ms. Blejer has reported in their records. They are going out and identifying them. They don't have all 70 of them yet, but we have enrolled Mr. Blejer into the study that I think Dr. Sejvar described before, and so we should get a lot of benefit from the fact that Ms. Blejer has reported this to us and we're very grateful to her and to the rabbis that permitted this individual to undergo the autopsy to confirm it one way or the other.
I know that the secretary at the National Prion Disease Pathology Surveillance Center has worked -- Eileen was involved in making lots of calls, trying to arrange for the transfer of the body. There's been problems with ice and tissue mix-ups, but it's ultimately going to get to Dr. Gambetti, and Dr. Gambetti's analysis may shed some more light onto what the etiology is here, whether it's a typical sporadic case or whether there are some other issues going on here.
DR. BLEJER: I want to make sure you know. This is not about my husband or his case. This is not. When I was talking about the reportability, I want to make you understand that I'm a fighter and I fought to get it reported, but that actually it's really difficult to get it reported.
If you want to fund somebody, you fund something national. First of all, you make reporting mandatory in all 50 states and the District of Columbia.
Number two, you educate the neurologists and neurosurgeons. Don't leave it up to the CJD Foundation or all the other family foundations. You have to do this as a government because it doesn't make any sense to be relying upon the individuals who are suffering to do the reporting.
This wasn't about my husband, and I don't actually care about what comes out of it, other than to save a life by telling you what you have to do so that you actually don't have under reporting and so that Dr. Gambetti does have autopsies because otherwise you're not going to find out what's happening with the transfusions, with the BSE or anything else because if you don't autopsy them, you don't know.
DR. FREAS: Again, thank you very much for bringing your comments.
We would like to see if there's anyone else in the audience at this time who would like to address the committee.
DR. FREAS: If not, Dr. Priola, I turn it over to you.
CHAIRPERSON PRIOLA: Dr. Linden? No? Would you like to make a comment?
DR. LINDEN: I'd like to clarify the issue about reporting of communicable diseases.
CHAIRPERSON PRIOLA: Oh, please. Go on. This is open committee discussion.
DR. LINDEN: I have some passing familiarity with reporting of communicable diseases, and I'd just like to comment.
Well, for one thing, as with many, many other issues in life, it is partially a resource issue, and I'm not defending the current situation by any means, but I can just provide some explanation as to why we have the patchwork situation that we do.
For one thing, reportability of communicable diseases basically is a state-by-state issue so that we're going to have 50-plus, you know, different jurisdictions as to what is reportable as a communicable disease, and it is based on where the patient lives, not where the patient is treated.
So if somebody is treated in New York City but they live in New Jersey, that disease is going to be reportable to the New Jersey Health Department, not to the New York State Health Department, and likewise if they live in Nassau County and, you know, they're treating in New York City, it's going to be reportable in Nassau County Health Department, which will then come to the New York State Health Department. So it's really confusing as to where it goes, and if somebody is very far from home, it may not get back to their home health department.
And likewise in this case, I assume the same thing would apply. If somebody is treated in Washington, D.C., if they live in Virginia, it's reportable in Virginia, and those reports may not get always back to the jurisdiction of residence of the patients. So that can be really confusing. Different jurisdictions may have different types of cases be reportable, and the different jurisdictions may have different amounts of resources available to follow up on cases.
And I would also say the reporting to the CDC is voluntary. I'm not aware of anything that's mandatory to be reported to CDC, with the exception that we heard about the death certificate reporting earlier, and I believe we heard that there's not 100 percent reporting with that either, but I'm talking about just communicable disease reporting, morbidity cases, you know, as separate from deaths.
So I just wanted to explain a little bit more how communicable disease reporting works, and that, indeed, it's a real patchwork and it's not well understood. We get questions about it all the time.
CHAIRPERSON PRIOLA: Dr. Bailar. Oh, are you finished? I'm sorry.
DR. BAILAR: This is a problem that has to be fixed. Ms. Blejer's presentation and the discussion that has followed here show that the system is just broken. It isn't working.
It brings me straight back to my earlier question about the completeness of reporting. The bottom line is we don't know nearly as much about this disease, its frequency, its distribution as we think we do.
CHAIRPERSON PRIOLA: Dr. Nelson.
DR. NELSON: Yeah, I picked up on another issue that Ms. Blejer raised, and that was the issue of that her husband's neurosurgical history and possible dura graft, although it's unclear, but in terms of screening of blood donors, there is no question about past neurosurgical history. The only thing that is asked is do you have a family member with CJD, and they ask about dura mater grafts or growth hormone.
But possibly, I mean, the committee has spent the last two or three years, I think on revising and hopefully improving the donor history questionnaire, which has, you know, over 50 questions already, but it seems to me that somehow this should have been picked up at some point, you know, Mr. Blejer's history as a frequent blood donor.
And I think that our donor screening questionnaire, though long an cumbersome, is still not perfect, far from it. And I think we could ask a question about neurosurgery during a given period. Most people aren't awake when they have neurosurgery and, therefore, don't know what went into them or what didn't, but you know, it's not everybody that has had neurosurgery. I don't know what number, but I would suspect the number of donors with a history of neurosurgery during a certain interval is probably pretty small.
But nonetheless, and the risk of transmission of classical CJD is probably small, too, but from what we've heard today, I think we could improve the selection or deferral of donors with regard to this risk.
CHAIRPERSON PRIOLA: Dr. Wolfe.
DR. WOLFE: I know we're not supposed to have votes or questions, but I would just like to ask the question and maybe even subject it to a vote as to why, in the wake of this incredibly irrationally disparate reporting of this disease and the importance of the reporting, why by regulation or, if necessary, by law this country couldn't decide that there is mandatory reporting all over the country for this disease.
CHAIRPERSON PRIOLA: Dr. Sejvar, you had been waiting. Would you like to go ahead?
DR. SEJVAR: Maybe just to make a very quick comment on the issue of reportability, and this is frankly something that we hear quite often from families of people with Creutzfeldt-Jakob disease. You know, I mean, a couple of issues, one of which was raised a little bit earlier, that the reportability basically is a state domain.
I think the other issue is to have a condition be reportable is one thing. To have the physician come and make the diagnosis and then, you know, follow through and make the report is another, and so, you know, unless the diagnosis is made and then unless that person who has made the diagnosis actually follows through with the reporting, you can make a condition reportable all you want.
You know, I think that's one of the reasons that we have focused on several additional mechanisms for surveillance, in addition to, you know, making the condition reportable, but I think that it's important to keep in mind that simply making a condition reportable is one thing. Actually having the diagnosis made and then followed through is quite another.
CHAIRPERSON PRIOLA: Dr. Khabbaz.
DR. KHABBAZ: Yes, let me just add that I agree. I think Dr. Sejvar has articulated it well. Let me just add on that CDC is on record encouraging states to make reporting mandatory if based on their data they feel that that improves reporting.
There are some states where it is mandatory, and there's some experience with states where it's mandatory. Looking at the data, and Jim or Larry might correct me, where because of what Dr. Sejvar has told you, the reporting based on mandatory reporting is not as complete as in other instances where it is not, and it has very much to d o with diagnosis and other factors.
CHAIRPERSON PRIOLA: Go ahead.
DR. GAMBETTI: Again, I can give you the perspective of the center. I think that what Dr. Sejvar said is correct. I think we need a double approach, and this is the one that we have tried in collaboration with the advisor of CDC, but we have largely tried on our own to obtain, one, to raise awareness in the neurologists and pathologists of America, and that we have, therefore, sent a letter through the professional organizations, both pathologists, and we use five of these organizations, and the American Academy of Neurology.
Essentially should the membership of this association -- should essentially cover a large proportion of the pathologist and neurologist in the United States, emphasizing the need to report very early in the course of the disease as soon as the diagnosis is made, to report it to the state's health department and to us so that always through the caring physician we can follow the patient.
And if unfortunately the diagnosis is correct and the family concerned, we can arrange for an autopsy.
On the other hand, we have tried to contact the health department of all the states, believe it or not. We started with some states like Ohio, New York, now Washington, and California, and Oklahoma, I believe, and all agree, all agree to send the letter on behalf of the -- well, again, the states in which the disease is reportable, 26 states out of 50, agreed to send out a letter to the physicians of the state, especially to the neurologist, recommending on their own that as state health departments, that the disease or that the cases be reported to the state health department and to the surveillance center as soon as diagnosed so that it then can be followed.
This other state in which the disease is not reportable have been more kind of careful and, therefore, they have allowed us to send a letter on our own to the physician of the states, which we have done in some states.
And we are now in the process. Essentially we have covered about six states so far in which essentially we have an agreement that the letter will be sent and in another state it has been sent out already.
For the other states, we are working with the President of the state and territorial epidemiologist to send a letter or to ask the state to send the letter to all the physicians of the state. So we are working, trying to have this in all of the states.
However, my experience is that whether the disease is reportable or not, that is, whether we are dealing with the state and with the diseases are reportable or with the state in which the disease is not reportable, it makes a difference.
If the disease is reportable, the state will feel more motivated to really support the initiative of the National Prion Disease Pathology Surveillance Center, actually to endorse it.
In states in which the disease is not reportable, there is more caution because, of course, this is not something that can be easily endorsed if the disease is not reportable. My personal opinion is if there were a way, and I would really think I would support if there is a way to do it and perhaps there is a way. The disease should be reportable in all the states, and that would help, along with raising the awareness of the physician.
CHAIRPERSON PRIOLA: Dr. Wolfe.
DR. WOLFE: This is an interesting discussion, but I go back to what I'm saying. I think we really need to propose that either by regulation or by law it be reportable, and as everyone has said, and I agree, it isn't enough just to have it reportable. There need to be sanctions against these institutions.
These people die generally in hospitals, and there is no reason why as part of a reporting requirement there couldn't be some sanction that encouraged people to report.
I think this country has tried too many times to do important things on a voluntary basis and has shied away from making them mandatory, and this is an excellent example. If you think about all of the money, time, resources, brilliant people involved in this, and yet a very fundamental piece of it, namely, raising from 50 to 60 to 95 or 100 percent, which you know, who knows what sort of selection bias there is in the cases that are not getting reported. They may yield more information.
I mean, I don't want to dwell on this, but I really would proposed that we suggest that there be either by regulation or, if necessary, by law, mandatory reporting with sanctions for those that don't report.
CHAIRPERSON PRIOLA: Before we go too much further with this, I have to remind everybody that this is not something that's regulated by the FDA. So we can't really --
DR. WOLFE: We can make recommendations though.
CHAIRPERSON PRIOLA: Well, there are people listening who are hearing this conversation, but we can't do that, what you just suggested.
Dr. Schoenberger and then Dr. Linden.
DR. SCHOENBERGER: Let me just make a couple of comments. One is that CJD, because of the nature of CJD, is one of the better reportable diseases to CDC, and I say that because 100 percent of these cases die, and it's unusual in this country for people who die not to have a physician put down on a death certificate that they died of CJD.
We don't get them all, but as Dr. Sejvar pointed out, probably 85 percent plus come to CDC's attention, and there is the delay.
The other issues you should know about CJD, and it's illustrated by, I think, Ms. Blejer's experience, is she had trouble getting a diagnosis, and that is, in part, the nature of the clinical disease. When these patients come to the neurologists initially, they don't make the diagnosis of CJD right away. In fact, CJD, since it is 100 percent fatal, they often wait until they have a chance to see the entire picture of the illness, and the CJD disease and diagnosis is probably best made at the time of death.
And even then, after death, if you'd ask Dr. Gambetti how many of the cases that are submitted to him on autopsy of suspected cases actually get confirmed as prion disease, and I'll bet you he'll say, what, 40 percent or so?
DR. GAMBETTI: Sixty.
DR. SCHOENBERGER: Sixty percent do what, get diagnosed?
DR. GAMBETTI: Are confirmed.
DR. SCHOENBERGER: Are confirmed. So 60 percent are confirmed, 40 percent are not confirmed. So given that situation, to have this reportable in the same way that people, say, report measles or hepatitis, it sort of requires a different system, and the important thing is not whether it's reportable or not, but whether the state has the resources to follow up on cases to make sure it gets the full kind of work-up that it needs, and you need an extra bit of work-up in these particular cases.
And so we encourage states who are at least willing to put that extra energy into it to make it reportable if that will help them get the autopsies done and get the tissues in and so on.
In general, whether we get cases or not get cases is often a relationship issue between Gambetti and the various networks of pathologists and the states and their relationships with many of the states.
The proof of the pudding is, I guess, that many of the states where it's reportable don't do a whole lot better than those that it's not reportable in terms of the total number of cases that we get.
DR. WOLFE: There are no sanctions.
DR. SCHOENBERGER: Okay, and that may deal with a whole other issue of whether there are sanctions or not.
One of the real problems that I'm struck with is the whole problem of autopsies in this country. I know that when I went to medical school, you know, in training and so on, I'd say half of the cases that died would get an autopsy and we'd learn about, you know mistakes and what happened, and my sense is that today in the average hospital the number of people who die and get autopsied is well below ten percent, you know, maybe well below five percent, and I think that's a quality of care issue.
And so I'm dealing with a disease where autopsies are right now the only real way to definitively make the diagnosis and to confirm the case, and so in a sense, I feel like we're fighting a secular trend trying to go opposite, and I'm in a sense very pleased that we've been able to raise the number of cases that Dr. Gambetti has been able to see. If you look at his charts, they've been going up very nicely, and we want to continue that trend.
But, again, we've left it to the states to tell us whether making it reportable will help get the kind of information that we need, and we've been telling the kind of information that you need in this particular disease. And we've gotten funding for Gambetti. We've gotten funding for the CJD Foundation and all of these other ways to try to encourage this increased surveillance and the getting of this kind of information.
CHAIRPERSON PRIOLA: Dr. Linden and then Mr. Bias.
DR. LINDEN: In my experience, the compliance with reporting by hospitals is excellent. That's not where the problem is. The problem is with the local physicians in the community not reporting communicable diseases in ambulatory patients. So I don't think going after hospitals would be beneficial at all.
And I basically agree with what Dr. Schoenberger has said, that the reporting and finding the cases for this particular disease, actually we're doing a very good job, and I don't think the authority is remotely within the realm of this committee or FDA to be looking at a nationwide type of reporting. So I don't think it would be fruitful for us to really even get into that type of issue.
But I do agree that it might be fruitful to, you know, somehow recommend further efforts in the area of trying to get more tissues from these types of patients. You know, it seems like that has been a very fruitful type of effort and to do more of these epidemiologic investigations because we've been getting some very valuable information. If we can try to continue those efforts with the cooperation of the states, that's something that we could continue to encourage, you know, and recommend.
MR. BIAS: This is a little off the topic of reporting, but I wanted to bring it to the group's attention. Two of the presentations earlier spoke about how we hadn't seen any cases in the hemophilia or bleeding disorders population related to CJD, and I wouldn't expect to with the manufacturing processes today.
What I would suggest to the CDC is that you look at the group prior to the current fractionation processes. The individuals with bleeding disorders who received components prior to the current level of intermission is for the first time in the bleed disorders community that we're not the canaries in the coal mine, so to speak; that the rest of the blood supply is, and if you're going to find clues, you're not going to find it in the group of children and young adults who have been raised and using recombinant or monoclonal products. You're going to find it in those of us who are using component prior to that.
So I would suggest seeing some figures on that the next time the CDC presents what's going on with that group. It has got to be a small group because most of us haven't survived HIV and Hepatitis C and so forth, and it should be easily taken out of the data based on that.
And then in terms of the reporting issue, I'd like to remind everyone that the best way to encourage accurate reporting, it's a partnership between public health agencies and private family or nonprofit groups. You can't impose reporting. That won't work. You have to work at both sides of it and do it through collaboration, and that's what the CDC tires to do by supporting these various foundations.
So it's a partnership between family and public. If you simply levy sanctions and try and force people to report, they'll simply retreat. It just won't work.
CHAIRPERSON PRIOLA: Okay. Thank you.
I want to try to refocus this discussion back on the blood and blood products issue since we can't do anything about the reporting issue with this committee, but we can discuss it and bring up the problems, and I think where it perhaps overlaps a bit with FDA interests is in communication between blood suppliers and the various public health agencies enabling you to track any danger to the blood supply.
So maybe Dr. Epstein has some things he wants to clarify for us.
DR. EPSTEIN: Well, yes. I wanted to make a comment in that narrower context. Ms. Blejer pointed out the difficulty of identifying the case where an individual who later develops CJD had been previously a blood donor.
Almost always that information is learned from the family. We simply don't have a system in which there is any automatic tracing of records from the hospital back to donor centers. So that's not at all unusual.
We do, however, have required reporting. If a blood establishment becomes aware that a previous donor later develops CJD, the previous collected units are regarded as subject to what we call biological product deviation reporting, meaning that they did not meet a standard. Had the information been known at the time of donation, the unit would have been on unsuitable.
In that circumstance the blood establishment must report the fact of those units to the FDA. Additionally, when units are taken off the shelf, if donation was more recent, as has in some cases occurred, then they also are obliged to report these product withdrawals to the FDA.
We routinely will make that information known to the Centers for Disease Control. When the information comes by the other route, when the Centers for Disease Control becomes aware of a case of CJD, the CDC is well aware of the need for investigations to include the question whether the individual previously had been a blood donor, and that triggers an investigation of donation records.
So we do at least have a handle on that element of the reporting system, and we do have communciations that are needed so that the different components of the health system become aware of at risk units and of the need to enroll such index cases in the ongoing studies that we call "look-back" to try to find out outcomes in recipients, and those studies were already described by Dr. Sejvar and Dr. Schoenberger.
And then just one additional point. Ms. Blejer again mentioned the issue of screening donors for a history of neurosurgery. There was over the last three or four years a major effort to reexamine the standard donor questionnaire. The American Association of Blood Banks has sponsored what's called a uniform donor history questionnaire that has been submitted to the FDA for review and which we have accepted that can now be adopted by any blood collecting establishment.
The specific question whether to modify a current donor screen which asks if you have ever had a dura mater or brain covering graft was not modified in the recent update to the proposed uniform donor history questionnaire, and that was an outcome of an effort to determine whether it was practical to ask a more broadly stated catchment question about surgeries.
And it should be noted that brain surgery is not the only surgery where dura mater has been used. It is also used in tympanoplasty and various other neurovascular procedures.
But it was looked at, and unfortunately those who were doing the studies concluded that it was not going to help our system. I don't know the exact reason that was found. It may have been that it just yielded a very high false positive rate of reporting. So I can't clarify that except to say that that issue was examined, and we do remain today with a donor question specific to dura mater.
CHAIRPERSON PRIOLA: Dr. Nelson.
DR. NELSON: Which in this case failed.
DR. EPSTEIN: Well, we understand that it has low sensitivity. Not everyone will recognize or even know that they had a dura mater graft, but the flip side is whether a more general question about neurosurgery would be sufficiently accurate to be used on 14 million donors a year, and it has to do with, you know, sensitivity and specificity of questioning.
So I don't have the data in front of me. We can reexamine that, but that's how you'd have to frame the issue.
DR. NELSON: Yeah, I think it should be looked at again, you know, as to how sensitive and specific a broader question as a lead-in might be.
DR. EPSTEIN: Right. My only point here was that we haven't ignored the potential utility, but we could examine the reasoning that led to no current change.
CHAIRPERSON PRIOLA: Are there any other questions or comments from the committee?
I think all of this speaks to the importance of -- Bob, would you like to say something?
DR. ROHWER: This is back to an earlier topic, but I did want to clarify one point, and that is we discussed the issue of dilution at several points during the session, and I just want to point out that this method of limiting dilution titration does get at that question.
Some of these samples have one or two infections per hundred animals inoculated. This method absolutely could not work if we could dilute the infectivity away because, in fact, that's what we're doing here. We have less than -- in that particular case you have something like a tenth of an infectious dose per inoculum, and yet we're still picking it up.
You could take it a step farther, and we have always wanted to do the experiment and make another tenfold dilution and see if you could pick up the same titer again. This time you'd have to inoculate 1,000 animals to see it.
But my guess is you would see it because none of these titration methods, even the endpoint dilution titration method would work if you could dilute the stuff away.
CHAIRPERSON PRIOLA: Okay. All right. I think that we'll get ready to break for lunch here until about 1:30, unless anyone else has any other comments or questions.
CHAIRPERSON PRIOLA: Okay. So 1:30 we'll reconvene.
(Whereupon, at 12:48 p.m., the meeting was recessed for lunch, to reconvene at 1:30 p.m., the same day.)
CHAIRPERSON PRIOLA: If I could ask the committee members to take their seats please, we'll get started.
Our first speaker for the afternoon session is a very busy person even though she's retiring. She's on the committee and now she's giving a talk. Dr. Lisa Ferguson.
DR. FERGUSON: Good afternoon. I'm assuming this is on.
Okay. I was asked to sort of summarize our investigation and at least APHIS' part of the response to the finding of a case of BSE in the State of Washington just before Christmas, as we call it, "the cow that stole Christmas" because there were several of us who really did not have a holiday.
Anyway, so I'll go through some of our response, and then I believe my colleagues with FSIS and FDA are also going to address their part of the issue.
So next slide, please.
This is a very brief time line sort of of the whole event, and all of this actually started on the 9th of December 2003, when a Holstein cow arrived at a slaughter plant in the State of Washington, and we obtained a sample from this animal because she presented a non-ambulatory animal or as a downer.
That sample proceeded to our National Veterinary Services Lab, and on the 23rd of December we announced that we had a presumptive positive case of BSE.
We immediately began our epi investigation even though we were calling that presumptive at that point in time, but we sent the samples with one of our pathologists to the U.K. to one of the reference labs in Weybridge, and they graciously agreed to meet us on Christmas morning and looked at the samples and confirmed that, yes, we did have BSE.
On the 30th of December, our Secretary, USDA Secretary Veneman, announced a series of additional preventive measures that we and the department would take.
On the 12th of January, we actually declared an extraordinary emergency. For those of you who aren't familiar with out regulatory process that's really not quite as drastic as it sounds. That's really a mechanism for us to obtain some additional authorities and some additional funding that we had needed.
And then this, for the committee. You don't actually have this on your handout, this last bullet point I would change right before lunch because actually on Monday of this week we did announce that we have closed out our active field investigation in the State of Washington.
So let's talk a bit about the investigation and what animals and what we did. The index case, we based our presumptive positive diagnosis at NVSL on both immunohistochemistry and histopath, and my colleague Al Jenny, I believe, has copies of those slides, and he's up next. So we won't go into great detail there.
And as I said, this was confirmed in the U.K.
This animal was a Holstein dairy cow, about six and a half years old; was sent to slaughter due to calving complications. She calved towards the end of November and then was having some difficulty. She would fall down and she couldn't get up. She had some posterior weakness.
Actually in talking with the folks on site, it really does sound like in many ways sort of truly what you would expect for BSE with the way that she presented, but she actually presented at the slaughter plant as non-ambulatory, and as part of our routine surveillance, she was sampled due to the non-ambulatory status.
Our trace-back investigation determined that she was actually born in Alberta, Canada, moved into the U.S. as part of a disbursal sale from this herd in 2001. The herd in Canada was disbursed due to health issues of the owner there. He just wanted to completely get out of the business; so did a complete herd dispersal sale, and many of those animals did actually come to the U.S., and that's what we've been investigating since then.
She initially went into a dairy finishing herd there in the State of Washington and then moved shortly thereafter into the dairy herd in Mabton.
She had had four offspring over her lifetime both in Canada and in the U.S. that we know of, one a heifer calf born in Canada, but we were concerned about what had happened, what she had had after she had entered the U.S., and she had a stillborn calf in 2001 shortly after she entered. She had a heifer calf in 2002. That heifer was till in the index herd, and then she had a bull calf in 2003. This was the calf that she had right before she went down and before she was slaughtered.
And this calf had gone to a bull calf raiser close by there in Sunnyside, Washington.
Now, this next slide is a very busy chart, but this just shows you -- I don't know if I have a pointer or not -- shows the investigation actually on both sides of the border. So the big, black line there is the 49th parallel with north of it being Canada and south of it being the U.S.
The red is the investigation in Canada, and the blue is our side of the investigation, but as you can see -- I don't think this one is working. Okay? Okay.
This is the index herd in Calmar, Alberta with the dispersal sale in 2001. There were actually 81 cattle that we know came across on one certificate in September 2001, and these were the ones that we were primarily trying to track down.
I won't go through all of this detail. You can read a lot of this on our Website of the various different towns and where we found animals, but these were primarily the ones that we were tracking down.
There were some other animals dispersed from this herd, specifically up here in blue. There were 17 heifers that went through some of these dealers, and we weren't specifically looking for these heifers because we did not have specific information that said all of these animals came into the U.S.
The Canadians never really -- we're still working on some of that, but as we did our investigations and were doing herd inventories and different things, we did find some of these animals through the traces.
So when you see a little note in blue here that says "heifers found," that's part of these 17 heifers, and these were fairly young animals when they came into the U.S.
This just, so that you don't have to look at the busy chart, tells you exactly what animals we found and where. There were 81 animals in this shipment, and we found 29 of them, including the index animal.
This number tells you how many of the 81 that we found in each facility, but then this tells you the total number that we euthanized on each of those premises.
Now, this has gotten rather confusing. Everybody says, "Well, if you found this one, why did you euthanize 15?"
This was part of our epi investigation where sometimes it was a challenge to find these specific animals. We were dealing with different types of identification and different types of records. We were dealing with cattle dealers who sometimes -- they're not the top notch operators one would hope to see. So we were dealing with some real sketchy traces at times, and we would have sale yard records that said, "Yep, I sold, you know, eight animals over here, and I think she was one of them." That would cause us then to go to that herd, look at every animal in the herd, record all of the identification and then go back.
So in many instances we could say, "Yes, we know that that one is one of the 81 we're looking for." In some instances we could say, "Well, I know she's one of those three. So we're going to take all three."
So that's why you get these differences in numbers.
So out of the 81 in that index herd, 29 accounted for, as I said. We tried to do some estimates based on the age of these animals and normal culling practices in dairies, how many would we expect to find, and we tried to use that to help us decide when it essentially was not worth our time to continue the investigation.
So based on normal culling practices, we estimated that between 17 to 36 of these 81 animals might still be alive, and we found 29 of them. So we felt like that was doing very well.
The OIE, which is the World Animal Health Organization, actually identifies the animals born within one year, either before or after an infected animal, are considered to be at higher risk. These are the birth cohorts, pretty wide definition.
But in this 81, there were 25 animals that would fall into that OIE definition of birth cohorts, and we accounted for 14 of those 25 higher risk birth cohorts, including the index cow.
Again, based on normal culling practices, we estimated that 11 of those 25 higher risk animals might still be alive.
So just total numbers of animals that we depopulated, we did take out a total of 704 animals that we euthanized. We paid indemnity for the owner, and we disposed of them appropriately. Four hundred and 49 of those were on the bull calf premises. You remember that I said that the bull calf born to this animal had been sent over there, and 255 were what we called animals of interest. So these are the specific animals out of the 81 and then those others that could have been part where we couldn't narrow it down, and seven were part of that additional group of 17 heifers that I referred to.
In line with just tracking down the animals, we actually did some other parts of the investigation. Our colleagues in FSIS on Christmas Eve announced that they would do a Class II voluntary recall of meat. This included meat from all ten animals slaughtered on the same day as the index cow.
And our colleagues in FDA did a very extensive investigation for rendered product and feed. This animal when she was slaughtered, obviously, the meat from this animal went into the human food chain. The rendered product was picked up and rendered. FDA did find all of the rendered product that could have remotely contained any of the parts of this animal. Over 2,000 tons of rendered protein were disposed of, and they also did an investigation with the dairy farm and the rendering and feed facilities and found that they were all in compliance with the feed regulations.
As part of our investigation, we followed the lead of our colleagues in Canada, and we did invite an international review team to come in. We asked the team to review what we had done with our epi investigation and also to give us recommendations on policies that we perhaps should consider.
That's a very brief explanation of what their literal remit was. I believe a lot of that is still on our Website also if you want to read the actual remit to the committee.
So they were chartered as part of the Secretary's Advisory Committee for Foreign Animal and Poultry Diseases. So they delivered their report to the Secretary's Advisory Committee on February 4th, and what they said in this report, first of all, they commended us for the open and transparent manner in which the investigation was conducted and commended us on the way that we had handled some of the communication aspects of it.
But they did essentially say that both this case and the Canadian case from A-2003 are indigenous BSE in North America.
As I said, we had asked them to specifically look at our epi investigation and what we had done, and they did that and gave us these recommendations. Essentially they said we had conducted a very comprehensive epidemiological investigation that conforms to international standards, and they suggested that really all of the relevant information that we could get from that investigation we had already gotten, and they recommended that we stop all of our active tracing efforts, which we were already in the process of reaching that same conclusion. So we took their recommendation there and concluded our investigation.
They did commend us for the tracing and the recall of the meta and bone meal or the tendered product, and they also said that the trading and recall of the meat was consistent with WHO recommendations.
Then we got into policy recommendations, and they looked at various aspects of policy. Start off with specified risk materials, and they recommended that SRMs be removed from human and animal feed.
They did recognize that the interim rule that our colleagues in FSIS had already put out there removes the highest risk tissues. However, they did recommend extending that definition and essentially bringing that down in age. FSIS' regs. refer primarily to tissues from cattle greater than 30 months of age. The committee recommended we look at cattle greater than 12 months of age.
They commented on our non-ambulatory cattle issues and actions, and essentially what they said there, they strongly recommended that we maintain access, that that's a crucial population in our surveillance and encouraged us to maintain access to that population for surveillance.
Which leads into surveillance. They did confirm that targeted surveillance, looking in the high risk population, is the most efficient way to find disease if it is present, and they recommended that we make an attempt to test all cattle greater than 30 months in the targeted high risk population for a one-year period; so make an all out, intensive effort.
They did say that testing of all cattle slaughtered for human consumption was unjustified. However, they did say that random sampling of slaughter cattle greater than 30 months could be considered primarily to encourage disease reporting at the farm level. They also recommended that we adopt rapid screening tests and decentralize some of our laboratory facilities.
They looked at feed restrictions. They did recognize that we have had a feed ban in place in the U.S. since 1997, but they recommended that all SRMs be excluded from all animal feed including pet food, and they also recommended that all mammalian and poultry protein be excluded from ruminant feed.
Traceability, they recognized as we have that we need to improve our animal identification system, and the department has already made a commitment to do that.
And then last but not least, they recommended that a strong educational effort needs to be maintained essentially. We have done very strong educational efforts since 1990, but they felt like that needed to be strengthened and maintained.
So now I'm going to summarize a bit of what we have done in surveillance over the past several years and kind of what we're looking at or perhaps looking at.
Our surveillance has been targeted surveillance where we have tried to focus on adult animals in the highest risk population. Specifically, this is where we think the disease would be most likely to be found if it was here.
So that's where we have focused our efforts, and this has been done with non-ambulatory animals or downers, dead stock, those animals that are out in the field that have central nervous system signs or on farm suspects.
We work with various state veterinary diagnostic labs as they examine neurological cases. We also work with public health laboratories. If they're testing an animal for rabies and it's negative, they can forward that sample on to us.
And then we work with our colleagues in Food Safety Inspection Service, and if they condemn an animal that is presented for slaughter on an antemortem inspection for central nervous system signs, they will call us, and we will get samples from that animal.
Our surveillance goals. We've attempted to do our surveillance and set those goals at a level sufficient that we would find one case per one million adult cattle at a 95 percent confidence level. Now, we've done these calculations based on estimates of our targeted high risk population, and previously we were using an estimate primarily of the non-ambulatory cattle population.
We worked with the American Association of Bovine Practitioners several years ago to try and get an estimate of the non-ambulatory cattle population in the U.S. at any given time, and what came out of that survey was 195,000. So we were using that as our targeted high risk population for these calculations.
Last fall, in response to the finding of the case in May in Canada, we decided to broaden that definition and to try and do a wider estimate and tried to come up with numbers of animals that die on the farms, other animals that are condemned, and came up with an estimate of 600,000 animals that would be in that targeted high risk population.
It's really somewhat of a challenge to try to come up with those estimates, and we feel like that figure probably has a lot of overlap in it, but we wanted to be somewhat broader rather than too narrow.
And just as a reminder, we estimate that the adult cattle population in the U.S. is about 45 million.
So based on sort of those assumptions that I just gave you, we calculated our goals, and when we did that calculation based on the non-ambulatory animal estimate with 195,000, the goal -- and we used this for our goal in FY '02 and '03 -- was 12,500 samples.
When we used that broader estimate of the targeted population, and we did that to try to set our goals for FY '04 before disaster struck, and we came up with a goal of at least 40,000, because if you run that same calculation with this higher estimate, the actual statistical calculation is 38,462 samples, and we just rounded that up to be 40,000.
So these are our surveillance numbers for the past several years. We have been doing active surveillance since 1990. In '02 and '03, once you put those numbers on this slide, it really skews the slide. So you lose a lot of this detail down here. But in fiscal year '02 we had 19,990 samples; in '03, 20,543 samples.
Now, this bar for 2004 is actually the start of fiscal year 2004. For those of you who are not in a regulatory agency, the fiscal year starts in October. So this is essentially the first quarter of fiscal year 2004, and we had 8,150 samples.
We have tried to focus our surveillance and set our goals based on regional estimations. Early on when we started surveillance, we were reporting things out on a state-by-state basis. We recognized that was somewhat misleading because many times if you're obtaining a sample from a slaughter plant or from a rendering facility in a given state, it's reported as coming from that state, but the animal had actually moved in from the state next door or the state two states over.
So we tried to work with our field people to define regions based on what we knew of adult cattle movements and then set goals for each of these regions based on the adult cattle population in the region.
Very busy slide, and I won't go through all of the numbers, but this just shows you what the goals here in the darker were for each of the regions in fiscal year '01 through fiscal year '04, and then the samples that we had obtained to meet those goals.
And in most regions, we exceeded our goals, with one exception that I know everybody always points out if I don't do it beforehand. In fiscal year '03, our northwest region goal was 1,200, and we got about 781 samples.
So let's look at the different populations that those samples are obtained from, and a significant proportion of our samples have been obtained from the non-ambulatory cattle population. So this purple bar are the non-ambulatory or the downer animals.
And as you can see, in fiscal year '02, out of about 20,000 samples total, about 15,000 of those were non-ambulatory animals. About 2,700 of them were dead stock.
A similar type thing in '03. Out of approximately 20,000 samples, a little bit more than 16,500 were non-ambulatory animals, and a little bit more than 3,000 were dead stock.
Let me make one point here, however, that I think has gotten somewhat confused in a lot of the discussion over the past several months. Not all of those non-ambulatory animals are those at slaughter, and there has been a lot of concern about how we will maintain access to that population.
Now, we recognize that a significant proportion of them have been obtained at slaughter because that's a convenient way to do that. You have a captive population right there, but there are other outlets for those animals with salvage type plants and rendering facilities, and we have been obtaining samples at those facilities also.
So we are committed to maintaining access to that population, and as we develop our plans for the future, we'll build on that experience that we already have in working with those alternative outlets for those animals.
Next slide, please.
Future policy changes. We continue to evaluate the international review subcommittee recommendations, and we are working with our colleagues in Harvard, with the models that they have done to compare the conclusions of the two different groups, I guess.
We're also considering a range of options on surveillance. We recognize that there's lots of different things that we could do. We have made no final decisions yet, but we are looking at a wide range of those.
In the meantime, our field folks are still continuing to get samples, especially from deads and downs as they can find them.
And we're also, as I said, continuing to work with the states, industry, and others to maintain access to our targeted population, and we recognize that all of those affiliated industries and our colleagues in the states will really be crucial in helping us maintain surveillance at whatever level we finally decide will be our final goal.
I believe that will wrap it up for me for now.
CHAIRPERSON PRIOLA: Thank you, Dr. Ferguson.
Are there any questions from the committee? Dr. Bailar.
DR. BAILAR: Over the period of a lot of years there have been many suggestions that the U.S. have a system for identifying individual animals. As far as I know, nothing has been done along those lines.
Would such a system have helped here?
DR. FERGUSON: Well, in some ways that's a difficult question to answer, and actually I wouldn't characterize it that nothing has been done. I mean, we've been making efforts towards a national identification system. Those efforts have now been significantly speeded up.
DR. BAILAR: As a result of this, yes, and you know, having a national ID system and having computerized databases with, you know, 100 percent recording of each and every piece of ID that was on an animal, yes, that would have helped. You know, that's not something that's going to happen overnight.
I want to make a point. These animals did have identification. It's just that they had a metal ear tag. They had a bangle tag. You know, they had different other numbers, and sometimes one number got recorded on one piece of paper and another number got recorded on another piece of paper.
DR. BAILAR: As far as I know, there is no national system for tracking these things, and showing when they move out of the population as slaughter or dead.
DR. FERGUSON: Well, that's what we're working on with the national animal ID program.
CHAIRPERSON PRIOLA: Dr. Gambetti.
DR. GAMBETTI: Lisa, is it fair or not to say that you examined essentially ten percent of the downers or you were examining ten percent of the downers at the time that the BSE case was discovered? Do I understand correctly the data? It looks to me that the downers are estimated to be 200,000, and you were examining about close to 20,000, 16,000 or so.
So is it fair to say or not that if you had examined all of them, now we would have ten cases rather than one or BSE?
DR. FERGUSON: I don't believe that would be necessarily fair to say. Actually I think about all we can say about our surveillance and the calculations that we have done is we believe we are doing surveillance and continue to do surveillance at a level sufficient that if there were one case per one million adult animals, we would find the disease. We're not saying we're trying to identify true prevalence or even any prevalence. All we're saying is if it was out there at that level, we're pretty confident we would have found it, and we did find it.
CHAIRPERSON PRIOLA: Dr. DeArmond.
DR. DeARMOND: I don't know how to ask questions with regard to this because it's very complicated, and I talk to a lot of people, both cowboys, guys who run ranches, people who have computerized microchip systems that they can subcutaneously put into animals, consumers, the whole group, and they're all frustrated.
Certainly the pharmaceutical industry continually calls and asks, "Well, we got our tallow," or, "we got our collagen from a certain place." They can't even identify the place usually. They're worried that it's contaminating their products, and they've already invested huge amounts of money into it. The public are aware of this, and they're upset about it.
Those of us who still eat beef are upset that we are never sure of whether the beef is BSE free or not. It goes on.
There's lots of concern, and no one is confident that they can be assured that the products even in the United States are free at this stage because of this one event, nor is it clear what the difference is between sporadic BSE and acquired BSE, and how we're ever sort that out, we don't even know what the incidence, unless you can tell me the incidence of sporadic BSE in the cattle population is and how we would even identify it, and even if we could identify it, is it transmissible to humans or is it like sheep scrapie? It just doesn't seem to go across.
So as I say, it's more a frustration that I'm sort of venting, but I don't know. There are lots of questions, and there are lots of ways of solving this. For instance, are there certified ranches and processing plants in existence in the United States where people could be assured that they have BSE free cattle, where cattle are universally tested so that the pharmaceutical company could go to them and get whatever parts they wanted, that even a Mexican restaurant in San Francisco could get brain and serve it in a tortilla, whatever they serve it in?
Is there anything like that? And how could we get to that stage, and shouldn't we get to that? Should there be tax benefits to ranches that do this and to processing plants that go the extra mile to assure the public that their product is free of BSE?
So I'm just asking for a simple --
DR. FERGUSON: Yeah, right.
DR. DeARMOND: But is your answer yes?
DR. FERGUSON: That's about the least simple question I've ever heard.
DR. DeARMOND: But it is the frustration of the public.
DR. FERGUSON: Well, no, trust me. I recognize that, you know. I mean, we've been dealing with this since December 23rd with the public, and actually I do have to make one point though, that you know, really consumer confidence in the U.S. has not dropped significantly, which is very encouraging.
And in the Canadian situation, a similar type thing. Consumer confidence really did not drop, and I believe that reflects on, you know, control measures that had either already been in place, educational efforts that have been in place for many years, and then subsequent actions that we have taken.
I think your question about, you know, defining free herds, defining free whatever, actually I think some of that gets into the next topic, Topic No. 3. I think some of that about risk based sourcing.
I guess while I have the microphone, I'd just caution everybody to be very careful about what do we mean when we say BSE free. That's a very difficult distinction to make with any of the TSE diseases. That's a very difficult point to make.
And, you know, it will be interesting to see how a discussion goes.
Your question about sporadic BSE, that's still an unanswered question out there, you know, in the whole TSE community. On the one hand, you can make the argument, well, wait a minute. If there were spontaneous cases of BSE in the U.S., we had all of the appropriate conditions to really propagate an epidemic and see a similar type thing that happened in the U.K., yet we didn't.
You know, does that mean that spontaneous BSE doesn't occur? No, I don't think anybody can say that. You could say spontaneous BSE is something different than the agent that they had in the U.K., and it's not transmissible in this same way. That's one of those unanswered questions that will either be out there for a while or will depend on the researchers to answer it for us.
DR. DeARMOND: But the public wants us to answer those questions, which means, I think, increased testing to try to sort out these questions.
CHAIRPERSON PRIOLA: Okay. One more question from Mr. Bias.
DR. GAMBETTI: Just echoing what Dr. DeArmond was saying, there is also another issue that is not only the American consumer, but also the country that imports from United States, which may really at a certain point require a kind of reciprocity in the level of testing that they do in order to import American beef.
And I don't know what your ideas are about this issue.
DR. FERGUSON: Well, we are also well aware of that. I mean, we've been dealing with the trade issues actually even before the 23rd. We had some of the fallout from the Canadian case.
I guess the way we have looked at it in our department, our surveillance has been an animal health measure, and it has been geared to identify the presence of the disease in the U.S. at a certain level, and that's really all our surveillance program is set up to do.
I would caution everybody at leaping to the assumption that testing equals food safety. I think that's really a bit of a challenge to make that leap. There are other measures that are really more accurate in assuring public health safety, and that such things as the feed ban to prevent spread of the disease, removing specified risk materials, those are relief of things that are primarily assuring public health and food safety.
MR. BIAS: I'm not surprised consumer confidence hasn't dropped considering the amount of McDonald's, Wendy's, BurgerKing, and the beef commercials that are running extra specials now on TV. So that doesn't surprise me at all.
But I'm wondering -- my question is a little bit simpler. Sometimes industries that provide blood or food for the American public sometimes benefit from a little extra scrutiny with the beef industry benefit from a little extra regulation, scrutiny, attention from the federal government in the next three to five years in terms of surveillance of cows.
DR. FERGUSON: Oh, man. That question probably should be asked to the beef industry, and I'm looking out there to see who my industry colleagues are in the audience, and I think they're hiding.
DR. FERGUSON: I think what we've recognized with this case and with the case in Canada is that sort of the livestock industry in general and all of our TSE management practices can stand a bit more scrutiny, and we need to look at what our policies have been, what we think the real risk is, and what policies we need to change, and we're in the process of doing that.
I think as you've seen, you know, with the announcements that we made on the 30th, with additional measures on the FSIS side, with measures done at the slaughterhouse, those are some of the policies that are being changed.
Has that increased scrutiny? I don't know, but it's adjusting the policies to address the problem as we need to do.
CHAIRPERSON PRIOLA: Okay. I think we're going to have a period of discussion after all of the speakers. So let's go ahead and move on to Dr. Al Jenny and keep your questions in mind for the general discussion part.
DR. JENNY: Okay. I went to a planning meeting to plan a new building and came back, and the pathologist that reads the day-to-day immuno said, "Hey, I've got a slide for you to look at," and he had already had the H&E made for the histopath. The IHC slide was very positive on this animal, and there definitely was spongiform change present when we looked at the H&E.
So my nightmare has been for the last ten years that because we do both deer and sheep and elk and cattle all in the same place, that we'd get a deer or a sheep that somebody called a cow, and so my first question was: is this really a cow?
And we do have totally separate cutting areas. So the cattle are done one place and the other species are done someplace else, and we have color coded cassettes. So if it's a yellow cassette, it's supposed to be a bovine. If it's an orange cassette, it should be a sheep.
So next slide.
And this is the immuno slide from this animal, and where you see red staining is where we have the PrPsc. So this is basically white matter here. This is gray matter here. You can almost just by where the staining is, you can pick out the gray from the white, and that's with the TSE. It's like real estate: location, location, location, and so you're looking at you want to make sure that your lesions or your staining are in the gray matter and with specific nuclei within the gray matter.
So next slide.
So the first thing we did, we went back and recut from that initial block. We also cut in additional tissue from the bottle for both tests, and then we didn't have the frozen tissue. A lot of times frozen tissue is retained by the submitter and only sent in if we ask for it. So we called the submitter and asked for that frozen tissue to come in.
So both the recuts and the additional tissue process were positive by immunohistochemistry, and we had good spongiform change by histopathology.
So the next slide.
So when we say it's a transmissible spongiform encephalopathy, spongiform says sponge-like. So you're looking for basically holes, but not all holes are created equally, and not all holes are a disease. So you have to be careful, and you have to know that the hole you're looking at are holes associated with disease in the right area of the brain, and in this case we also have gliosis. So that is another feature that we see with the TSCs.
So the next slide.
Again, very nice holes, very nice spongiform change in this brain.
And when again you go back to location and you're looking at specific nuclei within the brain at a given level for these lesions and so every nuclei that you go to you could find some of the spongiform change.
This is artifact, and again, not all spongiform, not all holes are real spongiform change associated with disease. So you have to know what you're looking at and something about the tissue.
So next slide.
And now we're back to the immunohistochemistry. We've been using immunohistochemistry to do our screening for quite some time. We started out doing histopath only. Then we switched to where we do both histopath and immunohistochemistry, and then we basically screen mostly with immunohistochemistry, now with histopath on the ones that CNS or nervous system signs are reported.
So routinely we're just doing the immuno, and again, this is the gray matter. This is the vessel. This is gray matter. This is white with some gray mixed, and very, very, very distinct staining. No question that this is positive.
These are neurons, and you can see we have staining around neurons and throughout the gray matter.
More of the same.
And this is the dorsal motor nucleus of the vagus, just about as intense staining as you'd ever hope to have.
So next slide.
Again, this is a white matter track. So it's not staining. The red is the gray matter where you see the staining.
So that's it.
Oh, okay. We did get the frozen tissue. We did have Dr. Dr. Richt at the National Animal Disease Center do the Western blot. It was positive, and we are doing one of the rapid tests just on a developmental basis at NVSL. So we did it on the biorad rapid test, and it was positive on that test. I think that was it.
Okay. So according to our plan the BSE response plan, the initial case was going to be confirmed in England by pathologists that look at BSE routinely. So the immuno and histo slides were taken to Weybridge, to that lab, agency lab there, and their pathologists agreed to come in on Christmas day. They spent about ten minutes looking at the slide and said, "That's it."
And the phone call came back here that they agreed, and so that converted it from a presumptive to a confirm.
CHAIRPERSON PRIOLA: Okay. Thank you, Dr. Jenny.
Are there any questions? Dr. Bracey.
DR. BRACEY: I was just interested in what is the cost of performing the screening test per cow, per animal?
DR. JENNY: The cost of the testing?
DR. BRACEY: Yes.
DR. JENNY: The testing itself is around $20 per animal, but you have all of the other associated cost of getting the sample, getting it there and those types of things.
DR. BRACEY: Oh, okay. Thank you.
CHAIRPERSON PRIOLA: Dr. Bailar.
DR. BAILAR: If I understand the dates correctly, it took you about two weeks to do the preliminary testing before you sent the stuff to England. If you were doing this again, would you send it earlier in the process?
DR. JENNY: It wasn't two weeks. We actually didn't do the sample, didn't actually run the sample until the 22nd. The 22nd was the first day we saw that slide.
The next day we saw the tissue that came out of the bottle, and we were sure that we had the right animal. So that was the 23rd.
The sample went to England on essentially Christmas Eve, the 24th, and England gave us a positive on the 25th.
DR. BAILAR: Well, then I should change my question to ask about the long delay before you got it. Is there reason to try to shorten that a great deal?
DR. JENNY: Definitely, definitely.
DR. BAILAR: And are you taking steps to do that?
DR. JENNY: Yes, yes.
CHAIRPERSON PRIOLA: Dr. DeArmond.
DR. DeARMOND: Those are very nice slides, but why couldn't you be convinced that they were correct? Why did you have to send them to England?
And there are people all over the United States that would look at that and say they're correct.
DR. JENNY: Because the plan, which has been in place since early in the '90s, had the first case going to England. So we followed the response plan that had been developed for BSE, but we didn't wait for England to say it's positive before we did the -- we started doing the follow-up tracing on the animals.
CHAIRPERSON PRIOLA: Dr. Ferguson.
DR. FERGUSON: Actually I think Al just said some of it. I wanted to make the point that we didn't wait for the U.K. confirmation. We were extremely confident in what NVSL had reported to us, but in addition to it was in our plan, that's actually also sort of the precedent that has been established by other countries. It's general when you find that first case, you have it confirmed at one of the world reference labs. So we just followed that precedent also.
CHAIRPERSON PRIOLA: Okay. Thank you, Dr. Jenny.
Our next speaker will be Dr. Mary Porretta.
MS. PORRETTA: Good afternoon and thank you.
I'll just make one correction. I'm not a doctor. I'm actually an attorney, and I work in the Policy Group at FSIS, and I'm going to give an overview of some of the new regulations and policies that FSIS implemented to further enhance our safeguards against BSE.
Okay. Can I have the first slide, please?
The mission of the Food Safety Inspection Service is to insure that meat, poultry, and processed egg products are wholesome, not adulterated, and properly marked, labeled, and packaged.
The provisions in our regulations issued in response to the detection of the BSE case on December 23rd are intended to prevent human exposure to the BSE agent through consumption of meat and meat food products.
The next slide, please.
On January 12th, 2004, we published three interim final rules and a notice in the Federal Register. All of the regulations were issued as emergency interim final rules, and they were effective immediately upon publication. So these regulations have been in effect since January 12th.
Next slide, please.
The interim final rules have a 90-day comment period, and it closed on April 12th, 2004. After the comment period closes, and this is standard procedure for any regulations, FSIS will analyze all of the comments received in response to the regulations, and we will later publish another document in the Federal Register that would include a discussion of the comments received and any amendments that we would make to the regulations in response to those comments.
The three regulations in the policy documents, the first one is entitled "The Prohibition on the Use of Specified Risk Materials for Human Food and Requirements for the Disposition of Non-ambulatory Disabled Cattle."
The next regulation is meat produced by advanced meat recovery, bone separation machinery, and meat recovery systems. That's regulations related to the advanced meat recovery process.
Next slide, please.
The third regulation is a prohibition on the use of certain stunning devices used to immobilize cattle during slaughter.
And then the fourth document is actually a policy, a notice that we issued on informing the public of our change in policy on animals or cattle that are tested for BSE under APHIS' surveillance program that are being tested at the slaughter establishment.
Okay. So the first rule deals with specified risk materials and non-ambulatory disabled cattle. So I'm going to deal with those two aspects separately.
The prohibition on these SRMs for human food, it designates certain materials from cattle as specified risk materials, declares that those materials are inedible and prohibits their use for human food.
Next slide, please.
The materials that we designated as SRMs include the brain, skull, eyes, trigeminal ganglia, spinal cord, vertebral column, excluding the vertebrae, the tail, transverse processes of the thoracic and lumbar vertebrae and the wings of the sacrum, the dorsal root ganglia often cattle 30 months in age or older, and the tonsil and distal ileum of the small intestine of all cattle.
To insure complete removal though of the distal ileum, we are requiring that establishments remove and disposed of as inedible the entire small intestine.
Establishments that slaughter cattle or that process the carcasses or parts of cattle are required to develop, implement, and maintain written procedures for the removal, segregation, and disposition of specified risk materials, and they are to address these procedures either in a HACCP plan, a sanitation program, or another prerequisite program.
The slaughter establishments and processing establishments, we operate under a HACCP inspection system where the industry comes up with plans to insure that food safety hazards do not get into meat food products as it verifies their programs, and that's just what that last bullet is about.
Next slide please.
Establishments are required to maintain daily records that document the implementation of monitoring of their procedures, and then FSIS verifies the adequacy and effectiveness of their procedures, and that would be through reviewing their records and looking at the procedures, observing the establishment, how they are implementing the procedures, observing carcasses to make sure that specified risk materials have been removed.
Next slide, please.
Under the regulations, materials are deemed to be from cattle 30 months of age and older unless the establishment can demonstrate that the materials are from an animal that was less than 30 months at the time of slaughter. So, you know, they can choose to treat all animals as if they're 30 months of age and older and remove specified risk materials.
If they choose to segregate, they have to demonstrate to our inspectors that, either through documentation or dentition, that they can determine the age of the cattle. And, again, we would verify that they're doing that appropriately, and if they're not, they would have to take corrective actions.
All of these regulations are codified at 9 CFR 310.22.
Okay. Next slide.
Now, the second part of this regulation deals with the disposition of what we call non-ambulatory disabled cattle. In this regulation we defined non-ambulatory disabled livestock as livestock that cannot rise from a recumbent position or that cannot walk, including, but not limited, to those with broken appendages, severed tendons or ligaments, nerve paralysis, fractured vertebral columns, or metabolic conditions.
So it's really regardless of the reason for the non-ambulatory status. Non-ambulatory disabled cattle cannot go for human food.
Next slide, please.
As I said, the carcasses of non-ambulatory disabled cattle are prohibited for human food. Non-ambulatory disabled cattle that are presented for slaughter will be condemned, and under our regulations condemned cattle cannot be taken into an establishment and cannot be slaughtered or dressed in the establishment.
The other regulations that we issued are with regard to advanced meat recovery and another product called mechanically separated beef.
AMR Technology is the technology that enables processors to remove detached skeletal muscle, tissue from livestock bones without incorporating significant amounts of bone and bone products into the final product.
When properly produced, under the regulations product derived from AMR systems is comparable to hand deboned meat, and it can be labeled as meat.
Under our former and new regulations, spinal cord, which is the high risk tissue, is not considered a component of boneless meat, but under the former regulations, beef AMR product that was found to contain spinal cord was not permitted to be labeled as meat, but it could be used for human food if it was relabeled as mechanically separated beef, which is considered as a meat food product. It's not considered meat, provided other requirements for MS beef format.
The new regulations just declare MS beef inedible and it's prohibited for human food.
Other requirements that we issued for meat produced by advanced meat recovery systems is vertebral columns and skulls, which are SRMs of cattle 30 months of age and older, cannot be used in the production of AMR product.
AMR product that's identified as meat cannot contain any brain, trigenital ganglia, spinal cord, or DRG. That's for all livestock and cattle under 30 months of age.
Meat produced using AMR systems cannot contain unacceptable levels of bony solids and narrows, and that's more because that's not consistent with hand deboned meat.
Next slide, please.
Again, as in SRMs, establishments are responsible for developing, implementing, and maintaining procedures to insure that the AMR process is in control, and those procedures must include observation of bones entering the system and testing of the product that exits the system.
And FSIS, we conduct regulatory verification testing of the end product for spinal cord and DRG, and if we find spinal cord or DRG in AMR product, that has to go for inedible purposes.
The third regulation that we issued was just a prohibition of the use of stunning devices, captive bolt stunning devices that would inject, deliberately inject air into the cranial cavity of cattle, and those were prohibited because the studies have shown that they can force pieces of brain into the circulatory system of the stunned cattle, which it could become lodged, and edible tissues such as liver or heart.
So although we're not aware of any establishments that are currently using it, that's prohibited.
And then the fourth, the policy statement that we issued, it's called our test and hold policy, and basically it states that FSIS will not pass and apply the mark of inspection to the carcasses or parts of cattle that are selected for testing for BSE by APHIS until the sample is determined to be negative.
We have issued a series of notices to provide additional clarification on the rules to our inspection personnel. Our policies and rules are available on our Website at those locations.
That's really it.
CHAIRPERSON PRIOLA: Okay. Thank you, Ms. Porretta.
Are there any questions? Dr. Nemo
DR. NEMO: How difficult would it be or how easy would it be for an unscrupulous owner of a slaughterhouse to circumvent these regulations? Do you normally have people on site that inspect?
MS. PORRETTA: Yeah, right, specially at the slaughter establishments there's an inspector on site at all times. So it would be difficult.
CHAIRPERSON PRIOLA: Dr. DeArmond.
DR. DeARMOND: So as I was walking around the cowboy antique show in Phoenix about three weeks ago, I heard the people talking, the cowboys talking about that looks like it's forbidden for us now to eat T-bone steaks because there's often a little spinal cord.
MS. PORRETTA: Right.
DR. DeARMOND: So what would stop a person at the slaughterhouse from chopping off the spinal cord and giving the rest of the steak? And so wouldn't the danger still be there?
MS. PORRETTA: You could get T-bone steaks from cattle younger than 30 months of age, which is where most of that product comes from anyway. The vertebral column for the animals older than 30 months are prohibited, and bone in beef from those older animals, they have to debone it.
DR. DeARMOND: So in reality, as I understand, cattle for food are usually slaughtered at 18 months of age in the United States, 18 to 20 months?
They're younger, in general, yes.
DR. DeARMOND: So as a general rule then these rules would not apply to them, except for distal ileum?
MS. PORRETTA: Right, the distal ileum for the animals younger than 30 months.
DR. DeARMOND: So the rule is pretty general. I didn't see an age discrimination in it so that in theory then the rule only applies to older cattle over 30 months of age, these new regulations?
MS. PORRETTA: Well, the definition of specified risk materials, certain materials except for the distal ileum are specified risk materials if they're from cattle 30 months of age and older.
DR. DeARMOND: So this shouldn't have a very profound effect on the beef industry then if they slaughter their cattle in the 20-month time period?
MS. PORRETTA: Depending on, right, what their practices are for younger animals, but it does have an impact in that they have to demonstrate to us that those animals are younger than 30 months of age, and that they don't have to remove the serums.
CHAIRPERSON PRIOLA: Okay. Mr. Bias.
Sorry, Linda. Do you want to add to that?
DR. FERGUSON: Yes, actually I would like to add to that because I don't want to leave the impression here that animals greater than 30 months of age are not slaughtered in the U.S. They are.
There are about 35 million animals slaughtered annually. Probably about 20 percent of that, between seven and eight million, are animals that are greater than 30 months of age.
DR. DeARMOND: So 90 percent of the living cattle are slaughtered each year? You said there were 45 million cattle in the U.S.?
DR. FERGUSON: I said there were 45 million adult cattle.
DR. DeARMOND: Adult, adult cattle. Of those 35 million are slaughtered?
DR. FERGUSON: No. There are probably about 100 million cattle total in the U.S., and of those, 35 million are slaughtered in a year, and of that 35 million slaughtered in a year, probably about 20 percent of that or seven to eight million are adult animals slaughtered greater than 30 months.
DR. JOHNSON: Two quick questions. One was the comment was made last year that there was a concern about fewer downer cows appearing, and the concern was that ranchers were burying the cattle on the land to keep from being detected. Is that still a concern, that is, the dead stock out on the ranch?
MS. PORRETTA: Yeah, I think actually Lisa can address that one better than I can.
DR. FERGUSON: Well, let's not equate, you know, downer animals and dead stock.
DR. JOHNSON: Yes.
DR. FERGUSON: There are some differences, and there are sort of two points to that. From a disease control standpoint for BSE, do we care if an animal out on the range is buried? No, we probably don't because that's not going back into the feed supply, and so the disease isn't going to be spread.
From a surveillance standpoint, yeah, we are interested, and that's the point that I was trying to make where we're working with various industries, and we're trying to revise our surveillance and really look at all of our options so that we maintain access to those targeted high risk populations, be they, you know, dead stock on a farm or downers that are now going elsewhere. We're trying to keep track of that.
DR. JOHNSON: The other question is that in Japan where they decided that all animals should be checked, they found several positive animals under age 30 months. Does that concern you?
MS. PORRETTA: Yes, and we did acknowledge that in what you call the preamble to the rules. We had a discussion on that. We did request comments on, as I mentioned, these are interim rules, and we are going to have comments on them, and we requested comments on that and would consider that.
DR. JOHNSON: Because one of them was only 21 months, right?
MS. PORRETTA: Right.
DR. JOHNSON: That would be a tremendous change if you lowered it to 20 months, wouldn't it? That would be impossible.
CHAIRPERSON PRIOLA: Mr. Bias?
MR. BIAS: I'm just a little concerned about the inspection process. It just seems I'm not inspired with confidence here about the inspection process.
I know that industries that are regularly inspected by the same series of inspectors become collegial in some ways in compliance, and I know in the blood industry when the FDA began to scrutinize the inspection process a little bit more effectively, that's when we really began to see changes in how the industry conducted their business, where they got out in front of potential problems as opposed to waiting for them to happen.
So I don't know if I have a question as much as a comment, that you know, if we're not levying fines, if there's no repercussion from having a cow show up on your facility that has BSE, if we are going to the herd and they are saying, "Hey, I think it's one of those five cows," and then we're reimbursing them for euthanizing the five cows, I'm not exactly sure we're doing anything to facilitate their cooperation or them getting out in front as an industry of the problem.
So I don't know. I don't think that's a question. It's just sort of the inspection process is not inspiring me to go out and buy a burger tonight.
MS. PORRETTA: I guess I don't under -- is your concern that the animals -- they're sending downer animals to slaughter or the inspection procedures that are inside the establishment to remove specified risk materials?
MR. BIAS: My concern is that the inspection process may have some lapses in it, and my concern is that the industry may not have the incentive to get out in front of these problems that we're continuing to talk about.
This could be a major health crisis for the United States. It's going to cause many lives potentially and certainly cost us a lot of money and to our health care system. And I'm just not inspired by the way the inspection process has been laid out here today that the industry is motivated to make the changes that I hear a lot of the committee members around the table asking about.
And I'm wondering if it's something inherent in our relationship to that industry that maybe needs to change.
MS. PORRETTA: Well, I know, I mean, in the plant if our inspectors don't believe that the establishments and effectively complying with these regulations, I mean, they have the authority to withhold the mark-up inspection, which means that that product can't be released for commerce.
MR. BIAS: Does that happen? Are there fines, things levied?
If I have a BSE cow, what happens at my farm?
MS. PORRETTA: Well, we are only at the processing establishments. FSIS does not go back to the farm. We regulate the plants, the processing plants, the slaughter and processing plants. We don't have authority on the farm.
MR. BIAS: And the USDA has authority on the farm, and you have authority in the plant, and where do the two groups meet?
MS. PORRETTA: Well, every animal that shows up for slaughter at our plants are inspected by an FSIS veterinarian and observed for any diseases. Those that have obvious diseases are condemned and don't go into the establishment and aren't slaughtered for human food.
CHAIRPERSON PRIOLA: Dr. Khabbaz.
DR. KHABBAZ: Yes, I'm just curious with regard to the regulations that you highlighted and the additional policy recommendations from the International Review Subcommittee. What are the Canadians doing? Are they doing the same, more, less?
MS. PORRETTA: Yes. We tried to make our regulations consistent with what Canada had implemented, and the list of SRMs are consistent with the Canadian list.
DR. KHABBAZ: So they're the same. Thank you.
CHAIRPERSON PRIOLA: Dr. Egan, would you like to make a comment?
DR. EGAN: Yes. From the Office of Vaccines at FDA, I was going to ask a similar question whether with the exception of the distal ileum, SRMs are defined only for cattle greater than 30 months of age. Is this the same definition that's used by Canada and other countries, that SRMs are only defined among the cattle greater than 30 months of age, or is it for other ages?
MS. PORRETTA: No, for the materials that we are designating as SRMs for cattle over 30 months of age, they are the same ones that Canada has designated. In Europe they use 12 months for most of the countries as the cutoff, and the Advisory Committee recommended that we consider that, and we said that's something we will be analyzing.
CHAIRPERSON PRIOLA: Dr. DeArmond
DR. DeARMOND: It's a question for Dr. Ferguson. Following up on Dick Johnson's question, there were these young cows in Japan, and I think there were some other unusual cases, but I haven't seen the data or looked at any reports on them, but I understand that the pathology and the distribution of protein was different than standard BSE; is that correct, or can you enlighten us on any of the pathology on those?
Is it U.S. BSE or something else?
DR. FERGUSON: I can tell you sort of. Well, I can tell you the information that we have, which is extremely limited, and I would like to make that point, that it's extremely limited, and there are a lot of unanswered questions about those cases. Probably the Japanese need to be the ones to answer that question.
What we had seen are essentially electronic digital images of histopath slides, and actually Al has seen these also. You really can't even quit tell exactly where they're from, you know. What section of the brain are you looking at?
And then again, digital images of the Western blot test that they had run. You know, just looking at those images of the blots, yep, there could be something there, but we also don't have information on what type of process did they go through to perform that blot. What exactly is going on?
So there are a lot of unanswered questions, and I think there are a lot of unanswered questions in the international community about those. You know, you compare that to what the Italians have recently done in the papers that they have published, you know, in regards to a new strain of BSE where they have lots of information, and they have sectioned the entire brain and, you know, look at all of this, and it's a very valid case.
But there are still questions about the Japanese situation.
CHAIRPERSON PRIOLA: One last question from Dr. Bracey.
DR. BRACEY: This question is more or less for my own peace of mind. Knowing the situation with the Japanese and the findings that they have, knowing that if you slaughter 35 million cattle a year that, indeed, the cost would be prohibitive, I guess I wonder is it truly impossible to test animals, thinking about economies of scale. As you increase the testing the cost will come down. The Europeans have said, "No, you needn't do this," but it sounds like there's a lot of uncertainty, and I'm just wondering. What is the determination that we've made that says that we cannot possibly test all animals? Is it cost? Is it inability to have a throughput? I mean, has this been carefully analyzed?
DR. FERGUSON: Well, I don't think anybody has said we cannot do anything. What we have said is there are lots of options out there, and we are evaluating those options.
However, talking about, you know, testing every animal, I think what you need to do is determine what you want your testing scheme to accomplish. What are you trying to do with that scheme?
Once you set that goal, then you build your surveillance scheme around that goal, and the points that need to be considered in going into that goal are: what do you honestly think the risk is in the U.S.? You know, where, based on science, where do you think you're going to find that risk?
And you know, the point there is in younger animals what the science tells us is to have disease, you know, sufficient either to have clinical disease or to get a positive test result in an animal less than 30 months of age, you have to have a pretty hefty dose given to that animal at a very young age. Do we honestly think that that happens in the U.S.? You know, and if so, what are we doing differently if we're going out and testing animals?
Those are all of the types of things that need to go into that decision about this is what we want our surveillance program to do. Once you make that decision, this is what we want it to do.
Then you look at the logistics of how you do it and, you know, how you set it up. You know, whatever can be done, I mean, it might take significant dollars; it might take significant restructuring of our infrastructure. Again, it depends on what do you want it to do.
CHAIRPERSON PRIOLA: I'll tell you what. Let's again save some of the questions for the general discussion so that we don't go too far, much more over time.
Thank you, Ms. Porretta.
Again, keep your questions in mind and we'll get to you.
Our next speaker is Dr. Stephen Sundlof.
DR. SUNDLOF: Thank you.
I want to express my appreciation for the opportunity to speak here today and talk a little bit about what the FDA's responsibilities are on the animal side on this issue. You have heard from the USDA, and there is an FDA component, and I want to talk a little bit about that.
We should move through this fairly quickly. I only have four slides. So if we can go to the first slide, please.
We've had a ban in effect since 1997 on the feeding of certain mammalian proteins to cattle as a measure to present the spread and amplification of BSE. We consider this to be one of our firewalls, the third of three firewalls, the first one being preventing the importation of any materials or live animals that may possibly harbor the infectious agent into the United States.
The second one that you've heard about from USDA/APHIS and Lisa Ferguson, in particular, is the surveillance program to detect the presence of the disease in cattle should it occur in the United States.
And the third firewall is to prevent the spread and amplification through the prohibition of any infectious or potentially infectious material that may get into animal feeds.
Now, since this disease is only spread among cattle through contaminated feed, we're fortunate that, in fact, we have one choke point where we can really gain control over this.
So in 1997 we promulgated a rule that said that no mammalian protein can be used in the feed of ruminants, which include cattle, sheep, goats, and certain other animals. There were some exceptions to the rule. Milk and milk products were exempted from the rule because the data had indicated they were not capable of transmitting the disease. Blood and blood products, gelatin.
We also said that if a rendering firm, for instance, only renders swine or horses and no other animals, then since there have never been any TSEs reported in those animals, then those products could go into ruminant feed, but if there was any mixture of any other animals, then that couldn't happen.
So that, and then the final exemption was plate waste, and that consists of salvage from the restaurant, food that was presented for human use had been cooked, presented for human use, and then not eaten. There are firms that come and collect that material, reprocess it, and part of that can go into animal feed. We exempted that practice as well.
I will tell you a little bit about what we are proposing, but just to talk somewhat about our inspection program, one of the things about having regulations is they're only as good as your enforcement strategy, and we spent a lot of our resources, about $20 million a year in programs that are designed to inspect all of the firms that handle this prohibited material. That would include renderers, feed mills, protein blenders, and a few other industries.
Every one of them in the United States that handles those materials gets inspected on an annual basis.
We also inspect a large number of other firms, some of which don't handle the prohibited materials and others, such as on the farm cattle feeders. There are approximately a million cattle feeders in the United States, and so it's impossible to get down to that level. So we concentrate our enforcement efforts at the top of the pyramid, the rendering industry being at the very top of the pyramid, and then from there on down it is the feed mills.
This is the total number of inspections to date, 26,000 inspections, which consist of more than 13,000 firms or facilities that were inspected. The reason that that's a different number from the total inspection is because we go back to firms on a regular basis.
Of those, all of those firms that were inspected of the 13,000, approximately 2,000 actually handle the prohibited material, and as of January 20th, there were only five firms in the United States that are currently out of compliance on their last investigation or in their last inspection.
And so we have been talking about a 99 percent compliance rate, and those are the numbers that lead us to that conclusion.
We also announced the Secretary of Health and Human Services, Secretary Thompson announced on January 26th that, in addition to the feed rule that was passed in 1997, that we will remove some of the exemptions that currently existed.
One of those would be blood products. We are proposing to prohibit the use of basically it's ruminant blood products in the feed of ruminants. It says mammalian, but if you read the definition of mammalian in the Federal Register, we have redefined pure swine and pure horses as no longer mammals.
DR. SUNDLOF: So it gets a little bit confusing, especially if you're a biologist.
We've also moved to prohibit the use of poultry litter in cattle feed. This is a practice that occurs mainly in the southeastern United States and not many other places in the United States, but it is a relatively common practice.
The problem there is that prohibited protein can be used in poultry feed and the poultry feed gets spilled in the litter and the litter gets fed back to cattle. That is a potential hole in the firewall.
We also have removed the plate waste exemption. Once again, that was an area of potential vulnerability, and the final announcement, the final measure is to require dedicated facilities if, for instance, renderers or feed mills handle both ruminant protein and non-ruminant protein in the manufacture of feeds.
There is always some amount of cross contamination that can't really adequately be prevented in our view without requiring either dedicated facilities or dedicated production lines, plus some barriers to prevent any cross-contamination or carryover.
And so those are my remarks. Thank you.
CHAIRPERSON PRIOLA: Okay. Thank you, Dr. Sundlof.
DR. LINDEN: Could you please elaborate on the rationale for removing the plate waste exemption and how we have food that's suitable for human consumption that would then not be suitable for animal feed?
DR. SUNDLOF: Okay. Yeah, we get that question a lot, and thank you for asking it because it seems to be a big source of confusion. I can tell you we also get the question on blood and blood products.
Remember that cattle are exquisitely sensitive to the infectious prion protein, much more so than other animal species, including humans. The recent information that we've gleaned from the expert committee is that as little as ten milligrams, an oral dose of ten milligrams, can cause a disease in cattle. So there's a very large species difference. We also don't allow cattle to eat anything that is muscle-related. So we don't allow cattle to eat the same products that go into the making of hamburger and get rendered into cattle feed. We don't allow that either.
So there are clear scientific reasons why we prohibit certain products from cattle but yet allow those products to be used in human food.
CHAIRPERSON PRIOLA: Dr. Wolfe.
DR. WOLFE: At the risk of sounding like someone who's talking about the part empty glass instead of the part full glass, given that the vector for this whole mess in Britain was recycled cow parts or recycled animal parts, we and others have said and agree that the main focal point in terms of prevention has to be the ruminant feed ban, and you list on your slide there five places that were significantly in violation, and you know, whereas that looks fine, 99 percent okay, any one of those -- I mean, right now we do not have indigenous U.S. BSE cows. The one here is from another country, but one of those could easily have caused, because it was found in violation after it had been violated, could easily have caused in the right circumstances some cases of BSE.
But my question is simply what kind of sanctions are there against those five and (b) what further is being done. I mean, the GAO put out this report two years ago criticizing the ruminant feed ban enforcement. I'm just wondering what is being done to sort of get that number down and to really terrorize, which is what it should be, violators out of doing that by becoming one of the five, well, too bad. I mean, the damage that could be done by that is just extraordinary.
DR. SUNDLOF: Well, those are very good questions, and just to let you know that since the GAO report has come out, those numbers have really gone down. We were at about 25 percent of the industry that was not in compliance, and we're down to less than one percent, and just for a little bit further clarification and then I'll get right to your point, it is that of those five firms that are out of compliance, none of the material from any of those plants went into cattle feed. They were producing their product under conditions which could have allowed it to go into ruminant feed. Fortunately, I think four of the five were producing poultry feed, and they weren't labeling their product appropriately. So that it could have gotten diverted somehow. It could have. I mean they were selling to poultry producers.
But your point is well taken. We have taken a number of enforcement actions. We get the question a lot: why aren't you taking more enforcement actions? And my answer is, we have five firms so that there's not a whole lot, you know, that we can take because we're only dealing with five firms.
We have one firm that is under a court-ordered injunction right now. We have done 47 recalls of animal feed which constitute over 280 products. These are at the expense of the feed mills that produce them.
Those recalls are not isolated to small geographic areas. We've recalled all the way from the Middle East because these products move in commerce very quickly, and they move all over the world. The United States produces 60 percent of the animal protein in the whole world. So it is a marketable commodity, and to the extent that we have the authority, we prosecute.
You know, again, we have a graded enforcement policy in which there's first a warning letter followed up by more serious sanctions. Again, we do have one under court-ordered injunction, but I think the real disincentive, the real disincentive to the industry is not so much the FDA, but the fact that nobody buys their products anymore. We have had some examples where a feedlot accidentally fed some meat and bone meal. Not only could they not -- The feed company ended up buying the 20,000 animals, but it got worse from there. Nobody, no renderer would take the animals. It cost them millions and millions of dollars in the long run. So there are some built in incentives as well, but the point is well taken.
CHAIRPERSON PRIOLA: Dr. Hogan.
DR. HOGAN: You may have said this. I might have missed it. Are those 13-some odd firms all of the firms in the United States or is there a percentage? And are the inspections surprise or not surprise, that is, scheduled? And does that matter?
DR. SUNDLOF: They are surprise inspections. Is it the 13,000? The 13,000 represent -- they don't represent everybody in the United States. They represent everybody that is either a renderer or a feed mill that handles the prohibited material. So in that sense it is everybody.
It doesn't get down to the individual farmers, which are a million or so, but yeah, firms, absolutely, every one of them.
CHAIRPERSON PRIOLA: Dr. DeArmond.
DR. DeARMOND: Well, so meat and bone meal pellets or whatever are still being manufactured. What are they sold for now? What is kind of the range of what they're sold for?
DR. SUNDLOF: Most of the meat and bone meal that is produced does go into animal feed, and it goes into poultry feeds, swine feed, and pet food.
CHAIRPERSON PRIOLA: Okay. Thank you, Dr. Sundlof.
Our next speaker will be Dr. David Asher.
DR. ASHER: Thank you, Sue.
In previous sessions, we have just heard about a presumptive transfusion transmitted case of variant CJD in the U.K. and a U.S. cow with BSE. The next sessions are mainly devoted to the second event and its possible implications for the safety of FDA-regulated medical products.
We have asked two speakers this afternoon to present general BSE related risk assessments, and then tomorrow for the staff from several or our FDA centers to address the potential risk of BSE agents to specific classes of regulated products in responses of the agency in attempting to manage those risks.
Next slide, please.
We need no further convincing that exposure to the TSE agents in contaminated products poses a demonstrated risk to both humans and animals. Assessing the magnitude of the risk associated with the different products in situation is, therefore, very important.
Human blood risk associated with donors potentially committing CJD and of greater recent concern, variant CJD were discussed this morning and many times previously at meetings of this committee.
Now we turn to the risk posed by CJD, bovine spongiform encephalopathy, for animals and humans in the USA, taking into account the recognition last year of BSE in two indigenous North American cows originating from different Canadian herds.
First, Josh Cohen will review the assessment that he and his colleagues performed for the USDA to model risk for U.S. cattle, and it is infected cattle that pose the major risk for humans because of the ubiquity of bovine materials not only in the food supply, but also as ingredients in and reagents used to prepare drugs, biologics, and medical devices.
Next slide, please.
Steve Anderson of our Center for Biologics will then discuss the risk for humans in the USA posed by potential exposure to the BSE agent. Although he will address the possible risk to the general population, the implications for the safety of human blood and blood products, other human cell and tissue-derived products are clear.
Since 1987, the FDA has acknowledged that, based on an increasing number of studies showing infectivity in the blood of animals with TSE, there was a theoretical risk that blood of humans incubating CJD might contain the transmissible agent as well.
Aided by the advice of this committee, the FDA has recommended deferral of certain donors thought to be at increased risk for CJD, and since 1999, of donors who might be at risk of variant CJD because of substantial time spent in BSE countries.
The report of variant CJD in a transfusion recipient will not cause a dramatic change in thinking by the FDA because we've taken the theoretical risk of blood-borne infection very serious for years. It has increased concern about maintaining the safest possible human blood and similar products while assuring an adequate supply.
In view of the recent TSE-related events, we have asked Steve to reevaluate the risk of potential human exposures to the BSE agent.
Next slide, please.
And I'd like to thank Moira Ricketts and the WHO for this slide.
Until recently, the FDA has had the luxury of addressing and managing the second risk, the risk of exposure to the BSE agent through contaminated bovine materials in medical products by recommending that most such materials be attained from cattle in countries identified by the USDA as BSE-free.
The FDA did that through a series of letters and guidances starting in 1993 and informally for a couple of years before that, but now, without attempting to judge the BSE status of any particular country, I believe it's fair to say that there remain in the world only a very few countries with absolutely impeccable BSE-free status that have both general high levels of human health, including BSE surveyance programs, plus a capacity to provide the substantial amounts of superior quality bovine materials needed to support the manufacture of medical products acceptable in the United States.
So what now? Now we must at least consider the possibility of obtaining safe bovine materials from countries like ours, where the national risk of BSE in cattle, while estimated to be extremely low, possibly even negligible, is no longer universally accepted as being nonexistent, and that, after all, was the conclusion reached by the outside expert committee that was invited to review the situation by the USDA.
Our own FDA Advisory Committee, this committee, has previously discussed a similar situation. In 1999, you suggested that it should be possible to obtain material from U.S. sheep and goats safe enough to use for manufacturing injectable products even though our country is not scrapie free.
Next slide, please.
The first step in rational risk management should be risk assessment. For those of you here today who are, like me, consumers of risk assessments rather than professional risk analysts, I was asked to explain briefly in more or less ordinary English what quantitative or probabilistic risk assessments are with their advantages and limitations, and I'll try to do that.
After doing that, I'll review possible ways to reduce the risk of transmitting TSE agents through medical products, including a reminder of the general safeguards against BSE exposures provided by regulations and policies of the USDA and FDA. FDA has called those the BSE firewalls, the safeguards already in place to protect humans and animals and, of course, protecting animals from infection is arguably the single most important step in protecting humans from exposure to the BSE agent.
And there have been enhancements recently announced. Our previous speakers have just done that, but perhaps it doesn't hurt to repeat.
I oppose the talk by offering for the purpose of stimulating later discussion only, not as a proposed policy of the Food and Drug Administration, some possible additional safeguards that might be considered for bovine materials used in or to manufacturer medical products.
If additional safeguards are indicated for medical products, those should be considered seriously only if they are likely to be both necessary and effective for significantly improving product safety and practically feasible for implementation because many of the medical products involved are clinically very important so that continued adequate supplies must be available.
Next slide, please.
Risk assessment is often thought of as comprising three elements: assessment, management, and communication. Our two speakers this afternoon will assess, and tomorrow FDA staff will discuss regulatory efforts to manage risk. We won't directly address risk communication at this meeting, although perhaps we should.
Risk assessment has been described generally as including four steps: identification of potential hazards, characterization of the hazard, that is, attempting to understand the quantitative relationship between the magnitude of the exposure, and the frequency, possibly the severity of the adverse events caused, the so-called dose response.
Then estimation of the probable exposures to the hazard that might be expected in the population, and finally for information generated by the last two steps, a probable overall risk can be characterized or estimated.
Next slide please.
In assessing the risk of exposure to infectious agents in products, three elements are generally considered. The first of these is the source material or raw material, the risk that the material might be contaminated with an agent, and of course, materials from cattle that have never been exposed to the BSE agent should, absent some opportunity for later contamination, carry no risk at all for containing the agent.
The second element of risk is the manufacturing process, which may or may not have the potential to eliminate accidental contaminating agents either by inactivation or by physical removal of the agent, which then must be disposed of.
Some injectable products -- gelatin might be an example. You reviewed that the last meeting -- are highly processed, that is, exposed to chemicals like calcium hydroxide and heating that remove a substantial amount of TSE agents. Many plasma derivatives -- Dot Scott will review those tomorrow -- are highly processed by chemical and physical treatments that have a validated capacity to eliminate TSE agents from the final product.
Other products, like human red blood cells and live attenuated viral vaccines are delicate and cannot be harshly treated. A theoretical risk of processing also exists, the risk that an agent in the raw material might either bind selectively to some component incorporated into the final product or, as recently demonstrated by our committee, the Chairman and her colleagues, for cultured mouse fibroblasts exposed to strains of scrapie agent. The agent might even replicate in the cell substrate used to prepare some medical product. Fortunately, that has never been recognized to happen with cell substrates used to make medical products.
The third element of microbiological risk for products is the end use of the single dose volume, the total volume per course of treatment and lifetime use, and the route of infection.
Parenthetically, the easiest and most effective way to reduce risk by control of end use is probably to avoid inappropriate use of medical products.
A number of factors should be considered in assessing the risk of infection after an exposure to the infectious agents of TSEs. Years ago, Richard Kimberlin introduced the term "effective exposure to a TSE agent," meaning an exposure sufficient to infect an animal.
The factors resulting in such an effective exposure, and they are not really different from those affecting infections with other more conventional agents are the dose of agent, the route of exposure, and the susceptibility of the exposed host to the agent.
For discussion today, it's important to note that invasive exposures, introduction into the CNS or bloodstream or peripheral tissues, usually require less agent to infect, and injectable and implantable medical products are intentionally introduced into the body by invasive routes.
The last factor is host susceptibility. There is a so-called species barrier that doubtless conveys to some hosts a relative or even absolute resistance to infection with certain TSE agents adapted to other species.
However, one especially painful lesson of the BSE epidemic in the United Kingdom has been that the species barrier is variable, not always predictable, and not necessarily absolute. The species barrier may have protected people and their cats against infection with the scrapie agent, but it has not been completely effective in protecting both those species against infection with the BSE agent.
Next slide, please.
Now I want to introduce quantitative or probabilistic risk assessment, the kind of assessment coming up next. Such risk assessment's attempt to express risk as an overall probability by proposing scenarios, a series of steps or, perhaps better, missteps, a chain of accidents or system failures that must occur before an adverse event results, like, for instance, a human infection with a TSE agent.
The probability for failure at each step in a scenario is estimated, and then the final probability is toted up. For an assessment to be most reliable, quantitative data should be available to estimate the probability of failure at each step, and it can be very hard to estimate the probability of even simple failures.
For example, the rupture of some mechanical item like a rubber O ring, although search of quality control records or articles from engineering journals might help with that. It's even more difficult to estimate the probability of some infrequent biological event, for instance, the probability that single cow has been exposed to the BSE agent.
An assessment should take into account biological variability. For example, the possible variations in BSE infectivity content in tissues from one infected cow to another, and uncertainty, the many things, some of which we've heard about today, about BSE and variant CJD that are imperfectly understood.
One way to do that is by avoiding the temptation to estimate the probability of failure at each step as a single number, and instead to use reasonable ranges or distributions of probabilities. Doing that is often found annoying because we prefer to see simple estimates of what a risk is, rather than distributions of possible risks that might be, but the latter is clearly more realistic.
A well-constructed quantitative risk assessment has a number of advantages, one of which is that it allows a sensitivity analysis.
Next slide, please.
Not all quantitative risk assessments are structured in this way, but here's a brief, general description that may help to understand the general idea. Each failure step or assumption is described and assigned an estimated probability or, better, a distribution of probabilities. The probabilities for each assumption are varied, and then a series of final outcomes, final probabilities for the adverse outcome are computed.
When the failure pathways are multiple and complex, the number of combinations of probabilities for failure at each step is huge. That's why sophisticated risk assessments require special computer models, the concentrated efforts of institutions like the Harvard Center for Risk Analysis, and a long time to develop.
One major benefit of a well-constructed, probabilistic risk assessment is that it permits a sensitivity analysis that is systematically varying the probability of each step individually to see which steps have the greatest impact on the final likelihood of diverse outcome. Such an analysis answers the question, what might happen if the probability of some failure step has been seriously underestimated or over estimated and suggests the most effective actions to consider for risk management.
For example, the Harvard risk analysis identified ruminant feed controls as having a great benefit in reducing risk, although that was also the intuitive conclusion based on U.K. experience.
Next slide, please.
The greatest single advantage of quantitative risk assessments probably lies in their transparency. Other risk assessors can examine the underlying assumptions and scenarios used, and if they disagree they can change them, put them back into the model, which is usually made available and then compute the new results.
They also have a couple of weaknesses. If the data used to estimate the probabilities are not reliable, then the estimates may not be, and they must assume no surprises. Well, while we know that life is full of surprises, but ordinary nonquantitative risk assessments and expert opinions suffer from exactly the same weaknesses.
In my view, the single greatest weakness of probabilistic risk assessments is that they may appear to be more accurate than they really are. Presenting subjective probabilities as numbers with estimated uncertainties make them look very much like mean values with standard deviations, and they certainly are not.
Next slide, please.
A popular risk assessment used for medical products containing bovine components is one developed several years ago for PhRMA by Fred Bader and his colleagues. The FDA used it to estimate BSE risk for vaccines almost four years ago.
And I summarize here on the left side some of the steps by which the probability of BSE contamination of some material can be estimated, as well as the probability that a single dose or a total dose of the treatment with some hypothetical product might contain a human infectious dose.
The original model used single point estimates and did not account for biological variability or uncertainty, and I listed some of the uncertainties in the right-hand column to consider the next time that the model is used, but the model is transparent, and it is or at least it originally was made available to anyone who wanted to modify it. I know at least that was Fred's original intention when he developed the model.
The next slide, please.
One problem associated with all risk assessments is that they are susceptible to bias because the probabilities of failure at each step are assigned at least partially subjectively, and I list on this slide some of the common sources of bias.
But, again, nonquantitative risk assessments and expert opinions are subject to the same biases without the same transparency.
One way in which bias of a risk assessment may be balanced is to submit it for independent review by other risk analysts and to run it again using their assumptions. The Harvard BSE risk assessment was, I believe subjected to such an outside review.
Next slide, please.
Now I'll address the possible steps to reduce the risk of transmitting TSE agents in general and the BSE agent in particular through medical products. Assuring that animal-derived or human-derived source materials are free of contaminating agent serves to reduce risk, and that can be done in two ways:
First, by obtaining the material for animals or humans with a history suggesting a very low TSE risk. For human blood and plasma, that's controlled by donor questionnaire and deferral policies. For human tissues, by history, usually from a surrogate respondent post mortem.
For bovine materials, safety of sources probably has to be controlled by certification that all safety policies had been maintained. For some infectious agents, safety of source material can also be assured using a screening test, either a direct test for the presence of the agent in the material or by some surrogate test, most often an antibody test, as evidence that the host has been infected.
Unfortunately there is still no accessible and validated antemortem screening test for BSE in cattle or for any TSE in humans. Why not simply eliminate the problem at the source by removing potentially infected bovine-derived or human-derived material, replacing them completely with vegetable or synthetic reagents?
That certainly should be encouraged when feasible, but it's most appropriate during the initial development of a new product. For some established biologic products, including important vaccines, it's probably not feasible to replace traditional bovine components like fetal bovine serum. Even a one log drop in the yield of virus, something that might easily happen if calf serum were to be replaced with some synthetic substance in cell culture medium, a drop of that magnitude would probably be enough to render the modified product unusable.
Next slide, please.
Manufacturing methods that eliminate agents' contaminating source material can provide additional protection. Inactivation of agent is preferred to physical removal because of a theoretical risk for downstream recontamination of the product after the infectious agent has been removed.
In that regard, as this committee discussed during its last meeting, effective cleaning and decontamination of equipment and facilities used to manufacture medical products are also important.
Tomorrow Dot Scott will review these issues for the manufacture of blood products, but the same general risk reducing steps in the manufacturing products are also relevant to other medical products. I'll leave to Dot further comments on what constitutes acceptable validation of the ability of various single manufacturing steps to reduce infectivity, evidence required to accept the additivity of multiple steps based on different physical chemical principles, and the relevance of results from pilot studies to the full-scale manufacturing process.
We've also reviewed those issues here in the past.
Next slide, please.
One troubling question that frequently arises is this. Why spend so much effort in attempting to reduce risks that appear to be extremely small for products that have enormous benefits? I cannot pretend to understand the psychology of risk perception or management decisions, but over ten years ago, M. Granger Morgan, a well-known risk analyst, explained it this way in a Scientific American article.
In making risk-based decisions, people may operate using different sets of rules. The decision rules we ordinarily use or we think we use might be called utility-based. Estimate the benefit and the risk and accept a small risk to achieve a substantial benefit, but there is another set of decision rules that we may also be using, and those might be called technology-based rules.
Technology-based rules impel us to use the best available technology to reduce some small risks even further even when the cost of doing them is great. We are especially likely to require best available technology when trying to protect certain especially- vulnerable populations like healthy children too young to give informed consent and required to be vaccinated in order to attend school.
We want to afford children every possible protection and to maintain a high level of confidence by their parents. So we take extraordinary steps to reduce risk in products administered to them.
Next slide, please.
The BSE firewalls, a series of safeguards put in place by the USDA and the FDA and enhancement to those protections have already been summarized for you. I tried to list them together on this slide as well as reference to the series of guidances that we believe have further reduced risk issued from the FDA during the past ten, 11 years.
I also show here the agency responsible for them and the year the safeguard went into effect. At the bottom of the slide are the two planned enhancement to FDA regulations. The concept is that although no single safeguard against BSE is likely to be foolproof, taken together they should provide a very high degree of protection, reducing both the likelihood that cattle are infected, and if they are, that humans will be exposed to the infectious agent.
Several of those safeguards, those intended to reduce the risk of BSE agent infected cattle and contamination of low risk tissues with infected tissues should also reduce the risk that bovine-derived materials infected with BSE agent would enter the manufacturing process as used for medical products.
As I mentioned earlier, we might consider whether the bovine- derived materials used to manufacture injectable and implantable medical products, products administered by routes known to facilitate infection might require additional safeguards. In the past the FDA has recommended a special safeguard for bovine gelatin used in injectable, implantable, and ophthalmic products in addition to those safeguards for gelatin in oral and topical products.
So there is at least one precedent for such a special policy for medical products.
For purposes of discussion only, on the next slide are listed several possible additional safeguards -- next slide, please -- that might be considered if they're judged to be both necessary and potentially effective in maintaining safe medical products and are found to be feasible in practice.
We are interested in hearing opinions of the committee members about those and any other related issues.
At the last meeting it became clear to us that the concept of a closed herd of cattle remains without any consensus definition. So perhaps it would be more useful to consider instead whether medical products might be prepared using bovine-derived materials from cattle originating from some kind of select herds and perhaps select individual cattle and select tissues as well.
It appears that the United States is already moving towards some system of improved traceability for cattle. Perhaps it is not premature to encourage full traceability for select cattle use for medical products even before that is required for all cattle.
It is clearly desirable that select cattle have never been fed or otherwise exposed to prohibited materials. How might that be reliably certified? It certainly could not be certified unless the animals were fully traceable.
It would be even more reassuring if certified select herds had adequate surveyance, as well as active surveyance as well as passive surveyance for BSE, but how should the adequacy of a BSE surveyance program be evaluated?
Should there be additional firewalls for selecting cattle suitable for producing materials used in medical products, safeguards besides those already in place to maintain the safety of edible beef products? Is that really necessary when the risk seemed so small? If it is justified, what might those additional safeguards be?
Should we recommend using the products from cattle only younger than 30 months? If so, how much younger? Fetal calf serum, which is arguably a very low risk material is obtained at slaughter from the fetuses of older breeder cows. So age restrictions of that kind for such cows would be unfeasible and probably unnecessary.
Should removal of specified risk materials from younger select cows be required? If so, at what age? And you've just heard that the USDA outside subcommittee recommended that most specified risk materials be removed from bovines older than a year in intestines at all ages.
Should a test for abnormal prion protein be required for some cattle? If so, starting at what age? What tests should be used?
The USDA has not approved any rapid PrP test for use with bovines yet. It would certainly not be useful to test brains of very young cattle because specimens from cattle of that age have rarely, if ever, contained detectable abnormal PrP even when they came from animals infected with the BSE agent.
At any rate, we welcome a general discussion of those and other issues relating to BSE risk and the safety of FDA regulated medical products.
Last slide, please.
With that, I thank you very much, and I surrender the microphone to our next speaker.
CHAIRPERSON PRIOLA: Thank you, Dr. Asher.
Are there any questions or comments for Dr. Asher?
DR. DeARMOND: Several times you asked, are the safeguards necessary when the risks are so low, and for the small pharmaceutical company they're absolutely necessary, and again, I talk to a lot of them because one mistake, one traceable event that was related to a product they put out wipes out the company. It's gone, and so it's only because of our litigious society that the risks of having any medical procedure can destroy companies, as we saw with the silicon breast implants.
So I think it's a real risk to a lot of people who were involved in their livelihoods and so forth, even though the risk is very small to the individual population. In the quantitation of risk assessment, very little is placed upon importation of beef, although there was some alluding to it, and yet that was the main problem here in December. It was a cow that came in and some cows that came in from Canada.
Should those be treated differently? Should those be tagged somehow with a subcutaneous implant that can be followed anywhere so that we could understand which cows actually did come from other countries. So mostly it's kind of that second issue. What about importation?
In this, the United States tends to be a free trade type of country with a lot of trading partners. If we just were very strict about following a cow from a friendly country like Canada, should we do that so that we can continue to trade with them?
DR. ASHER: Someone, Lisa, might answer this. The likelihood of importing actual identified contaminated bovine products, identified bovine products, I think, has been relatively small since the import prohibitions on ruminant products from BSE countries were put into effect by the USDA.
Now, the importation of products containing bovine materials that are unknown to the importer and to the USDA is another issue, but of course, in controlling the source importation, as well as internal controls are very important.
At the moment, of course, we're left with only two countries in the world that are considered impeccable BSE-free countries and also have sufficient capacity and general level of animal health to provide the United States.
To me, one of the problems is going to be as we deal with a changing view of the situation in our own country is keeping consistency with other countries. Obviously I can't comment on specific trade policies with regard to Canada. I believe -- Lisa may correct this -- that boneless beef is now, at least from younger animals, is now permitted into the United States. Other bulk products are not.
The level of concern with regard to Canada was, I think, revealed at the last TSE advisory committee when it was made clear that we weren't proposing any new blood donor deferral policies for Canada, and there have not been substantial changes in importation of medical products from Canada that I'm aware of, although there has been some concern about that.
DR. DeARMOND: And yet a lot of the new regulations and restrictions on use of bovine products is a result of the events of December 23rd. It has nothing to do with what was going on in the U.S. It was what was brought into the U.S.
DR. ASHER: Yeah. Well, the concern with Canada, of course, arose on May 17th with their recognition of BSE in a breeding cow. To me one of the greatest concerns is that there have been two different herds, albeit both in Alberta, that have been implicated in BSE, and in Canada. Fortunately both of those are born before the feed ban so that there's still some hope that the feed bans in Canada and the United States, which are arguably inside the country the single most effective disease control mechanism might have -- they should have -- reduced the risk markedly, although it is one of multiple firewalls, and they're, of course, not foolproof. That was the impetus behind the enhancements that are planned for the feed ban.
DR. DeARMOND: I only make these comments because we saw lots of slides, lots of risk assessment and very little about importation.
DR. ASHER: Yes. Well, you're absolutely right. In insuring the quality of the source, the importation is very important, and that's why we stopped importing from BSE countries as soon as the magnitude of the problem became clear.
CHAIRPERSON PRIOLA: Okay. Thank you very much, Dr. Asher.
I'd like to just reinforce, I think, to the committee that what Dr. Asher just discussed is sort of at the heart of what we're supposed to be considering and discussing today, and that is looking at the adequacy of the current safeguards and then based on the scientific merit trying to determine the risk benefit and feasibility of any additional safeguards that might protect products regulated by the FDA.
Now, we're running a bit behind time. Dr. Asher's talk was actually scheduled for 30 minutes, but we're running behind time. So my question is this: should we go on through or should we take a ten-minute break? This will be the only thing the committee will vote on this committee meeting.
CHAIRPERSON PRIOLA: What would you prefer do? A ten-minute break?
Okay. We'll take a ten-minute break and reconvene at ten till four.
(Whereupon, the foregoing matter went off the record at 3:44 p.m. and went back on the record at 3:59 p.m.)
CHAIRPERSON PRIOLA: Okay. If we could get all of the committee members back at the table, we'll start with the next presentation, which is Dr. Joshua Cohen, and since these next two presentations are both associated with risk models, maybe we'll do the two talks and then ask questions after both talks have been completed.
So if Dr. Cohen is ready.
DR. COHEN: Well, I'm glad Dr. Asher gave a lot of the background on some of the general issues dealing with quantitative risk assessments, which we usually don't have the luxury of going into all of those issues. If you can keep them in the back of your mind, of course, it's pretty relevant to what we did.
If you could proceed to the next slide, please.
Just first, I want to recognize a bunch of the folks who worked on this project with me and George Gray, who are still at the Center for Risk Analysis. We had a group of us up at the Center for Risk Analysis, also a team of investigators down at the College of Veterinary Medicine at Tuskeegee University.
So first some background, now, this model. How did this come to be? Why were we asked to do this?
Well, USDA was interested in the following questions. First, they were interested in identifying the possible sources of introduction of BSE into the United States cattle population. Of course, there was a good idea of what that was, but they wanted us to go through and review that.
And then to get more to the heart of what we were looking at, they wanted us to identify and quantify the relative importance of pathways by which BSE infectivity might spread among U.S. cattle. So the real question was: what happens once it gets here?
And to evaluate the implications over time of possible introductions of BSE into the U.S. agricultural system, in particular, this is how we expressed the question was really about was this co-called reproductive constant of the disease. If you're familiar with epidemiology, this is sometimes designated the R0 constant, and all it is is if you have one diseased animal, on average how many more diseased animals are going to result from that index case or any case in general actually?
If that number is less than one, then of course, the disease tends to die out over time. It may blow up temporarily if something unlucky happens, but the law of averages comes into play over time and the disease tends to die out if that constant is less than one.
If that constant exceeds one, then of course the disease tends to grow over time, and you can get a situation like that in the U.K. in the 1980s. So that is the real key question that we were after.
And then second to that at least causally is once you figure out how the disease circulates in the cattle population, what is the extent of human exposure going to be.
Next slide please.
So in terms of what the report history was, we first got involved in this in 1998. About three and a half years later, we released the report with USDA at the end of 2001.
During 2002, the report was reviewed under an independent contract with Research Triangle Institute through USDA, and they had some four primary investigators on that review, including John Wildsmith from the U.K., who was intimately involved with the U.K. outbreak during the 1980s, and the revised report was accepted by USDA and released several months ago.
So all right. What do we mean -- well, I'll get a little later to what we mean by a simulation model, but why did we use a simulation model rather than using statistical analysis, such as what was done in the U.K. by some of their investigators over there, or a qualitative analysis, something like that?
Well, you can't really do a statistical analysis for the United States because, well, until this past December, there are absolutely no data, and even now there has been only one case. So there's no information, no quantitative information on which one can model, statistically model the behavior of the United States agricultural system in response to a challenge, a BSE challenge being introduced into it.
Now, there are certain mathematical techniques that one can use rather than building a simulation model, but first, a simulation allows you to characterize the evolution of the disease over time, both within animals so that the disease moves from one part of the animal to another and the disease load increases and so on, and then, of course, through the cattle population over the years.
As I began to say just a moment ago, BSE is not amenable to conventional epidemic disease modeling. There are a series of complications, and, in short, the spread depends on how and when the animal was slaughtered, for example, and because of these particular issues that you need to keep track of, the math just becomes intractable or at least it became too hard for us.
Next slide, please.
A model allows you to quantitatively compare the importance of different pathways by which the disease spreads, and it allows you to evaluate different risk management strategies. You can turn things on and off. You can say, no specified risk material fed back to cattle or into any feed at all, and hence, could not get back to cattle through leaks in the feed ban.
And finally, through the use of sensitivity analysis, it allows us to identify where we need more information to better understand how the agricultural system would behave if BSE is introduced, which apparently it has been.
Next slide, please.
So what did we do? We started with the basic model, which is that somehow -- we don't know how -- in the U.K. scrapie may have crossed over into cattle or spontaneous development of BSE within cattle. Somehow BSE got started in the U.K., and then through feed and the recycling of feed the disease was amplified, and that was the basic model we started with, and we figured that if BSE came to the United States somehow, that would behave in a similar manner.
Next slide, please.
So we took that basic model, and we developed a computer model which has the following structure.
First, we consider the whole series of exogenous sources of infectivity that come into the cattle population. Cattle are slaughtered. They may die by other means as well. Some parts of the cattle go to human food. Some goes to feed. That division depends on how long it has been since the animal was been infected, again, because the disease moves from some tissues to different tissues as the incubation period progresses.
It depends on slaughter plant practices, and finally it depends on the animal's age because the animal's age is going to influence what the slaughterhouse does with the animal.
The material that goes into feed, some of that is going to go to uses that pose no risk to cattle in the United States, such as export, at least from the U.S. cattle population that becomes a non-risk or to pet food, and then there's going to be some feed that manages to get back to the cattle population through leaks in the feed ban.
Next slide please.
So what were some of the key assumptions we made? And this is very brief. The report is available on the Web where there is a lot more detail, but in brief, the exogenous sources we considered were imported cattle, imported feed, sporadic disease, that is, a spontaneous development of disease in cattle with no apparent outside source or cross-species transmission, for example, from scrapie.
In terms of the spread of the disease among cattle, we did assume imperfect compliance with the feed ban. We considered contamination of non-prohibited materials in mixed use facilities, both rendering facilities and feed plants.
We considered mislabeling of prohibited materials, and we considered misfeeding.
Next slide, please.
In terms of the infection probability, so now the material has gotten into cattle; what's the probability that an animal is going to become sick, given a certain dose?
We considered changes in exposure and susceptibility with age. So, for example, young animals are often the ones that have the greatest consumption of meat and bone meal. They also happen to be the animals that it's believed are the most susceptible to disease just, again, because of the biology of the animal early in its life.
In terms of the disease course, as I've been suggesting, the agent moves from some tissues to other tissues at the beginning of the disease process. It's in the gut and it moves to the central nervous system over time, and while that's happening the total infectivity load grows especially rapidly in the months prior to the development of clinical signs.
In terms of human exposure, we considered contamination of advanced meat recovery products and consumption of variety meats.
The model is probabilistic, as Dr. Asher was explaining, that is, a way of taking into account variability and uncertainty. What's illustrated in this slide is how we took into account variation, and here I mean variation in how history might unfold. So if you imagine infected cattle being introduced into the United States, different things might happen over time.
Those animals might be slaughtered before much disease or much infective agent develops in their body. That would be a good thing, or you might get unlucky. They might happen to be slaughtered at an advanced age when there's a lot of infectivity. They might go to a plant where there is both prohibited and nonprohibited material being processed. That material might be contaminated, or the material might end up on a farm where there is misfeeding.
And because of all of these different possibilities, when you run the computer model over and over, and for each scenario we looked at we ran it 5,000 times, different things can happen, and so you get a range of different results. So one of our key outputs, for example, was the number of infected cattle or the number of cattle that become infected in the United States during a 20-year history, and there were a range of values.
So this is what the output looks like, for example. So the horizontal axis is time going from zero years out to 20 years. This is the number of infected cattle, and it's a log scale, and so when you start out in that first year, you're almost certain to have ten infected cattle, and as time goes on different things can happen.
These are box and whisker plots of the output of the output of the 5,000 runs. The middle mark right here is the median outcome. The box represents the range, the interquartile range. So 25th percentile to 75th percentile for this particular output.
The whiskers are the fifth to 95th percentile, and then the Xes are values that lie outside that range.
So as time goes on, you get a spread. Different things can happen, and in the worst cases -- this happens to be an introduction of ten infected animals -- you get as many as 100 infected animals at some point, but over time that tends to die out. On average, if you average all of these results and add up all of the infected animals over 20 years, you get something like four new cases in the 20-year period.
Even if you increase the number of animals introduced, the number of infected animals introduced to 500 animals, you get a similar result. It takes longer for it to die out, of course, but the disease tends to die out.
Now, the important point here is that that key parameter, the reproductive constant, R0 almost certainly seems to be less than one. That means that we almost certainly would not get a U.K.-type situation, an epidemic blowing up in the United States.
Could you get additional animals infected? Yes. Will we get a million additional animals infected like in the U.K.? No. It doesn't seem that way.
The next slide.
In fact, here's the behavior of the system in terms of what's the probability that BSE is still present in the United States after 20 years as a function of the number of infected cattle that you introduce at the beginning of that period?
Well, if you introduce one infected animal, there is only one chance in 1,000 in these computer runs that after 20 years the disease is still present.
If you introduce 500, the chance is as much as ten percent, but that means that even if you introduce 500 animals, you end up with a 90 percent probability that BSE would be eliminated if that's the only introduction within 20 years.
And I should say that all of these introductions are hypothesized to occur after the 1997 feed ban was implemented. Talk about what happens if that isn't the case a little later in this talk.
In terms of human exposure, what's the total number of cattle oral ID-50s, which is our accounting unit for looking at infectivity. A cattle oral ID-50 is the quantity of infectivity which, if orally administered to a bovine, has a 50 percent chance of producing disease. The risk in humans is thought to be much, much less. Nobody knows exactly how much less, but substantially less.
The total number of ID-50s to humans in our base case where we introduce ten animals was 40 ID-50s to humans over that 20-year period, and this is how it splits out so that we also know which types of food are the most important sources. Advanced meat recovery is the largest source, and that's because, well, lots of people eat AMR meat.
But this number, you've got to remember, we don't know exactly how many ID-50s went to humans in the U.K., but it has got to be many orders of magnitude larger than that since there were 200,000 animals there that displayed clinical signs and perhaps a million that were infected overall, and it wasn't for many years that the U.K. and the scientific community in general understood that this was something that we needed to worry about in terms of human exposure.
We also looked at risk management scenarios to see how they would decrease the number of additional infected cattle and how they would decrease human exposure; so a ban on specified risk material. So, in other words, we're just going to incinerate that material or something, totally get rid of it. That reduced the number of additional infected cattle by 90 percent. It reduced human exposure by 95 percent.
A ban on the rendering of animals that die prior to slaughter. That was a surprising one for us. That reduced the number of additional infected cattle by 80 percent, human exposure by only 20 percent, and that's because these animals weren't going to human consumption anyway, but they do potentially have a lot of infectivity because they're animals that die on the far. One reason they might have died is that of BSE, if they died of BSE, that means they had a full infectivity load.
We conducted a sensitivity analysis, a pretty extensive one, as Dr. Asher described. So here are a whole bunch of parameters that we looked at, and what we did is we looked at what happens to the results if we take the worst plausible value for each of these parameters one at a time in this particular slide, and the good news is that this happens to be the result, the total number of cattle infected, excluding those ten initial imports, and the result. Here's the average.
And remember in the base case, the average was around four, which is right here, and so for most of these assumptions you put the worst case value in, and it barely budges the result.
However, there are a couple. This one, I think this was -- I can't remember which one. This is the render factor. I'm sorry. Yeah, perhaps it's the render factor. That's how efficient rendering is at reducing the amount of infectivity in material that increased the projected number of animals a little bit, like four up to six or seven.
But the ones that made a big difference were leaks in the feed ban. When you have leaks in the feed ban, things are not nearly as good.
You get a similar picture when you look at potential human exposure. Again, and remember, this is a log scale over here. So a little move up in this direction, you know, like from here to here, is a factor of ten, and so, again, leaks in the feed ban lead to substantial changes.
So here are the key findings. First of all, following an introduction, the incident tends to decrease over time. R0 is less than one. After 20 years, BSE is most likely eliminated from the United States, and the results hold regardless of the source, whether we're talking about live animals being imported, contaminated feed, whatever.
After you get that initial insult, the number of animals with disease tends to decrease.
Now, I will say the sensitivity analysis, if you put some worst case assumptions together, especially with regard to the feed ban, you can get R0 greater than one, but you have to make a number of pessimistic assumptions for that to happen.
Human exposure is limited. As I said, it seems to be orders of magnitude less than the U.K., and here are the sources most responsible for human exposure.
The risk mitigation measures that we looked at that seemed to be most effective were eliminating CNS material from animal feed and human food, and stopping the rendering of animals that die before slaughter.
The key sources of uncertainty, as I mentioned, have to do with compliance levels with the feed ban.
I will say that we were coming up with these parameters in like the year 2000 or so, and it seems just based on some of the information I've seen at this meeting that the FDA and USDA, they've gathered some much more extensive information about compliance, and it looked pretty encouraging to me, at least what I saw in thee slides. So perhaps the feed ban is in pretty good shape.
I just want to spend a few slides here. I think it's four slides in all, talking about some work we did this past year looking at the Canadian BSE case.
We considered here various introductions of BSE into the U.S. from Canada, both live cattle imports, contaminated feed imports, and we also considered introductions from time before the feed ban. We ran the model out through the year 2020.
And this slide describes how the results, how the number of infected cattle from introducing five infected cattle, how the number of additional infected cattle depends on when the introduction occurred. If the introduction occurred here in 1998, most likely you get very few additional animals. However, if it occurred as early as 1990, well before the feed ban, and things had a chance to get going when R0 was greater than one, then the number of infected animals can be much greater, in the very worse cases even up in the area of 1,000.
Human exposure, a similar type of picture. Again, if we are fortunate and the introduction occurred later in time, the number of animals or the total amount of human exposure is quite limited.
So our findings were timing of introduction matters a lot. Contaminated feed produces more cases than imports of infected animals, and that's because if you imagine five cattle being imported and then slaughtered, well, not all of their remains is going to go to cattle feed. Even in the era before the feed ban was put into place, there were other uses for meat and bone meal.
Virtually all of the introductions -- and this is, you know, the not so happy part -- virtually all of the introductions yield too few clinical cases to be confident that they would have been found by surveillance. So, you know, what does that mean?
Don't forget those animals that I was showing you in those plots on the preceding slides, those weren't necessarily all clinical cases. A bunch of them were likely slaughtered before they developed signs. So they had disease, but there's no way they could have been detected by surveillance.
The introduction of the feed ban in 1997 reverses the growth and starts the prevalence of disease towards zero. So again, even with those early introductions, if you trace out what happens over time, the disease goes up and then it turns around a little after 1997 and starts heading back towards zero.
And I think -- is there another slide? I think that's it. That's is.
CHAIRPERSON PRIOLA: Thank you, Dr. Cohen.
DR. EPSTEIN: Dr. Cohen, could I just ask, if I could, have you attempted to validate the model by putting in input parameters compatible with the U.K. to see if it predicted the bovine epidemic curve in the U.K.?
DR. COHEN: What we did do, we did not do that with the U.K., but we did do it with Switzerland because there was information that we could use there to trace what happened with the outbreak, and with our very first shot, in other words, we did not play around with the parameters at all. Our first guess, we were within a factor of two of the total outbreak, which is really close in this business, and we had the timing down really well. And with changing some parameters which are certainly within the range of uncertainty, we are easily able to reproduce what happened.
Now, does that mean that the model is valid? It certainly doesn't guarantee it at all. You know, in this business, you can easily be right for the wrong reasons, and you can't necessarily generalize the results.
But we felt that it at least gave us comfort that the model wasn't completely out to lunch, and we're not either, I guess.
CHAIRPERSON PRIOLA: Dr. Linden.
DR. GAMBETTI: I wonder whether you can clarify for me this statement that you have in the findings. Virtually all intervention into too few clinical cases to be counted, that they will be found by surveillance.
Now we know that by testing what is ten percent of the highest risk animal, one was found. So in view of this, you would say that your model is not valid anymore or has to be corrected for this finding?
DR. COHEN: No.
DR. GAMBETTI: Can you explain it for me? Probably I missed something somewhere.
DR. COHEN: All I meant by that is that ex ante, so before December when all we knew was there were cases up in Canada or a case up in Canada and there were a lot of cattle moving across, there could be an introduction in to the United States. If that happened, would we know that it happened?
In other words, if it happened and our model correctly predicted what happened, would we be guaranteed of finding it?
And the answer as far as we could tell was, no, we couldn't be absolutely sure that we would find it. Does that mean that we absolutely wouldn't find it? No.
Now, actually if I can just take this moment, I want to say one thing about that animal that was discovered because I've gotten a lot of calls, especially from the media, people trying to figure out, well, what does this mean in terms of the total number of animals in the U.S. that might have BSE.
And I'm sure that's something that's on a lot of people's minds, and it's very hard to say. As Lisa Ferguson said, the purpose of the surveillance is not to nail down exactly how many animals are infected in the United States. It's to detect a certain number.
But you know, that said, I think someone in the meeting said, "Well, if we tested ten percent of the animals and one was sick, does that mean that there must be around ten?"
Well, that depends on extrapolating from this animal to the rest of the 200,000 nonambulatory animals that are slaughtered each year, and there are problems with that. This animal may be at particularly high risk because it was born before the feed ban.
Now, I don't know what the distribution of ages is among other downer cattle, but if they tend to be younger, then they would, I think, tend to be at lower risk, but that's just sort of a, you know, don't hang your hat on that. I just want to say that extrapolating from that one animal to a total number in the United States is tricky business.
DR. GAMBETTI: Well, wouldn?t it make sense then to test all of them so eventually you know?
DR. COHEN: Well, I think, first, you know, I completely agree with what Lisa said. What you have to do first is figure out why are you doing this, and if your purpose of doing this is to figure out what the prevalence is, then you have to have a plan for figuring it, for nailing that number down.
But then you have to ask yourself, well, why do you want to know the exact prevalence. I mean, isn't it good enough to know that the disease is here at some modest rate and based on that, we are taking these steps?
If we knew that there were ten animals or 100 animals, would that change the risk management actions that FDA is taking already? I don't know. We're not in the risk management business. I just throw that out as the type of question that, you know, folks like you and FDA need to be thinking about in terms of trying to figure out, well, what's the right way of going about surveillance.
CHAIRPERSON PRIOLA: Dr. Linden.
DR. LINDEN: Thank you.
Did you look at your key assumptions and attributes of the U.S. system to question, try to determine which of those were most significant in contributing towards the R0 being less than one in terms of like the feed ban, for example? I.e., if we had not had that, if you took that out of the equation, would we have been at risk? Does your model then turn out to have us be in the same situation as the U.K.?
I mean, did you try that modeling using a different set of assumptions and see what happens?
DR. COHEN: During our original project, well, actually there were some scenarios that we ran without the feed ban, not necessarily to see what would happen without the feed ban, but because the scenarios we were running just historically involved times before the feed ban, and what we found was that, you know, things blew up.
So although we didn't set out to answer that question directly, you know, the answer was really clear, just as a byproduct of the other scenarios we were running. Yes, without the feed ban, things blow up and, you know, you could have the U.K. here.
CHAIRPERSON PRIOLA: Dr. Bailar.
DR. BAILAR: A couple of comments. First, the extrapolation from a ten percent sample to the hole depends critically on how that sample is selected.
DR. COHEN: Absolutely.
DR. BAILAR: If the inspectors are picking the animals that look like they might have BSE and ignoring the ones that are downers because they have a broken leg or whatever, then that may be a better sample than if it's just higgledy-piggledy.
The second comment is that if you're interested in trends, and I think we are, then there is a need for much more precise data. The difference between one, ten and 100 may not be critical for a single shot, but if you want to know is it going up or down, then you need much better estimates.
DR. COHEN: Well, first, I totally agree with your first comment, and that was the whole point of what I said. There are attributes of this animal that was selected that make it different from the other 200,000 downers.
As to your second comment, I think first the decision makers, the policy makers, the interested parties need to lay out, all right, what options are we going to be considering in terms of risk management. How is our selection among these options going to depend on what we know about the trend?
And if our selection among options depends critically on whether the trend is ten to 100 or, you know, whatever the result it, it's only then that you need that degree of resolution. In other words, the degree of -- you can always get more resolution by having more sampling, and the question is: how much resolution do you need for the decision you have to make?
There are other ways, in fact, of getting at whether things are getting better. If we understand whether compliance with the feed ban, for example, is improving or not improving, that would, I think, give us a pretty good handle on whether things are getting better or not getting better, and it might be easier to do that than looking for the needle in the haystack.
Now, again, I have not studied the sampling problem and, you know, the pluses and minuses of surveillance. That is outside of what we looked at, but I'm just trying to say that the solution needs to be tailored to the question, and the question is, what risk management strategy should be selected and what information do we need to know in order to select among them.
CHAIRPERSON PRIOLA: Dr. DeArmond.
DR. DeARMOND: It seems to me there are two important questions though. There is the one question from the agencies that overall incidents and the up and down of incidents, and then three is the perspective from the public, from the consumers, whatever. It's like the CDC. It would be very nice to know the incidence of SARS in the United States, but the public, they only care if the person next to them has got it, who is coughing on them.
So there is a reason to test widely in a sense to find those individuals that are right next to you or the beef products that you are going to have or the pharmaceutical agent that you are going to use.
As I say, there are two different questions, and they should have two different approaches.
DR. COHEN: You know, I agree with you completely. You know, there is a perception issue, and certainly with respect to our foreign trading partners, you know, that has been made real clear. I mean, if tomorrow we could demonstrate with 100 percent certainty that there's no BSE in the United States, that would be worth a lot to the beef exporters. So there is value to the information there.
So, I mean, that's exactly right. Now, I was not thinking about that, and again, this isn't my area, but you're right. If someone can sit down and say, "Hey, if we could show with this level of certainty that the prevalence is below X, then you know, these countries would open up to our imports again and that would be worth a lot to us," well, then you can say if we need to demonstrate that the prevalence is below X, our surveillance needs to be tailored in the following way.
So, again, you go from your objective to the surveillance program you need in order to address that objective, and there might be other reasons why we need to know beyond the two that you just identified.
CHAIRPERSON PRIOLA: Dr. Gambetti.
DR. GAMBETTI: Just for the record, the issue of one BSE animal versus ten was a question. I raise it as a question, not as a statement.
DR. COHEN: What -- what --
DR. GAMBETTI: You asked this question. I didn't make the statement.
DR. COHEN: The question?
DR. GAMBETTI: I didn't make the statement that if you find one animal and you test ten percent of the high-risk animal you'll find ten if you test all of them. I asked the question whether this was possible or not.
DR. COHEN: Oh, okay.
DR. GAMBETTI: Just for the record, just for the record.
DR. COHEN: All right, fine, and the answer is you don't know because it's not a random sample. So you can't extrapolate, and you have to make assumptions, and that's what makes it hard.
CHAIRPERSON PRIOLA: Dr. Schoenberger, do you have a comment?
DR. SCHOENBERGER: Yeah, I would say that there's a very important, but expensive risk management decision that has yet to be made in the United States, and that's whether to ban the specified risk materials from animal feed altogether, as has been done in Europe and the U.K. Their experience has been that without such a ban altogether, you do get occasional cross-contaminations.
So in making that decision, it may well be important to know the difference between one, ten or 100 infected cattle.
DR. COHEN: Maybe. I mean, I guess, you know, you'd have to structure out, you know, again what the decision problem is. We will take Option A if we know X is true, and we will take Option B if we know Y is true, and if we make a mistake, then our penalty is going to be this. So it's worth the following for us to be this certain, and as a result, we should do this kind of sampling.
So it's that sort of thinking that, I think, needs to be done, you know, because it's very easy to say, "Well, you know, if we just test more animals, then we'll know."
Well, why do you want to know exactly? Because you might find out that in order to know what you really want to know, you should have even tested more or fewer. You need to map out the problem. That's all I'm saying.
CHAIRPERSON PRIOLA: Dr. Will, do you have a comment?
DR. WILL: Yes, I would just like to ask a question, a short preamble. In 1996, when variant CJD was identified in the U.K., it caused major public concern, although we believed that the exposure to BSE probably happened years before in the 1980s, prior to the introduction of any measures to protect public health, though we couldn't be sure about that, and we still believe that.
The risk assessment you showed very clearly relates mainly to the events after the introduction of the feed ban in 1997. However, if a case of variant CJD was identified in the United States this year, it's highly likely that the exposure took place in the 1990s prior to the introduction of the feed ban in 1997.
So one of the questions I have to ask you is: what was the input into the risk of exposure of the United States to BSE? The reason I ask the question is that in Europe the GBR risk assessment originally suggested there was some countries, mainly in Central or Eastern Europe that were at very low risk of getting BSE because they had imported very little directly from the U.K.
But it then became apparent that they were at risk, and the reason was that there had been imports form other countries in Europe that were then BSE-free that exposed these countries.
When you look at the U.S. exposure to BSE, do you look just at the exports from the U.K. in the 1980s and 1990s or do you look also at exports to the U.S. from other countries, such as Germany, France, Italy, et cetera?
DR. COHEN: The response to that question, in general, is that we did not estimate the probability that BSE came into the U.S. We assumed that it came in. We assumed that as many as 500 animals came in because we really couldn't quantify what the probability of an introduction was from all the myriad of sources.
I mean, it appears that Canada is the one that we know about now. We just said if it gets here, what will happen.
Now, I said in general. There was one particular country that we considered in terms of probability of an introduction, and that was the U.K., and what we found -- I think these numbers are correct -- we estimated that there was around a one in five chance to some infectivity from the U.K. was introduced into the U.S. cattle supply and that there was some considerably lower chance, few percent -- again, I'm doing this from memory. I might be wrong ‑- that that actually resulted in a case here.
But, you know, the details of that are in the report, but again, the main point to keep remembering was our focus wasn't figuring out what's the probability that it got here. We assume that it would get here and what will happen if it does.
CHAIRPERSON PRIOLA: Okay. Thank you, Dr. Cohen.
I think we'll move on to the next speaker, who is Dr. Steven Anderson.
DR. ANDERSON: Okay. I'm going to talk about the work that I've been doing on looking at Canadian and U.S. BSE risk.
The next slide.
Actually this analysis I'm going to talk about is actually two sort of mini risk assessments in one study. So I was approached with two different questions. The initial question in May was: what is the BSE risk for the U.S. and Canada? So in Part 1 of the talk I'm going to talk about estimating the BSE risk by evaluating these potential exposure pathways in the U.S. and Canada, and I'm just going to sort of summarize things right now and say that this is mostly a qualitative analysis similar to the reasons that Josh pointed out.
It's really difficult to say when you're importing in animals and feed materials, et cetera, what the probability of actually introducing the BSE agent into the country is. So I'll talk more about that in a minute.
And then the second question of importance to us is what is the risk for the general U.S. population and what are some of the implications for the blood supply.
And we're doing this by estimating BSE exposure, human exposures, and the risk in the U.S. Now, this is a focus a little bit different from what Dr. Cohen was speaking about. We're focusing more on the human health side of things.
So next slide.
I thought I would give just an overview, and you've seen this before, and we've talked about cattle statistics and beef statistics, I think, earlier in the day. Total cattle in the U.S., about 96 million, 13 million in Canada, slaughtered population annually about 35 million, and about a tenth of that in Canada.
I think the one important fact on this that I'll point out is that we export approximately ten percent of our beef. Canada exports about 60 percent or more of their beef, and it's important to remember that about half of that beef comes into the United States.
The next slide, please.
Now, starting on our first part of the exercise, estimating the BSE risk, the exposure pathways that we're interested in are imports from BSE countries of these two things: live animals that we looked at and then mammalian-derived feed ingredients, mostly meat and bone meal and animal meals, et cetera, animal-derived meals, et cetera.
And then finally, a question about the U.S. and Canada. What are the things that are coming across the border and switching back and forth? And that has implications for the movement of potentially infected cattle and contaminated products back and forth. So if you have an infected animal or infected meat and you import or export that, you're actually moving the risk around and shifting it from one country to the other.
Now, in the actual imports, I'm going to focus mostly on the U.K. imports that came in since 1980, since from about 1980 to the early 1990s was the major portion of the BSE epidemic, and then BSE countries, mostly in Europe, since 1986.
The next slide.
I'm going to gloss through a lot of this information. I think we've seen it in some forms and just because of the lateness of the hour, but this is looking at cattle imports from the United Kingdom, and this is mostly before 1990 that these cattle were imported.
Total animals imported into the United States, 334; into Canada, 288. Disposition of about 50 percent of the animals was known. Disposition of the others are unknown mostly.
And I think one important thing to remember is that there was a BSE positive identified in one of these cows from the U.K. in 1993, and Canada, I think, has accepted imports from U.K. farms with known BSE cases, and those animals numbered ten animals, ten cows from U.K. farms with known BSE cases.
So I think just looking at this, you can see that there is a potential for importing risk into this country of the BSE agent, but looking at this, you can't really tell what the probability is. You know, are all of these animals infected? It's likely not the case. It's only about .1 percent was the incidence in animal herds in the U.K.
So it's very difficult to predict from looking at these was an animal actually imported or not. It's hard to say.
I think one thing we can draw, the conclusion that we can draw is the risk at least seems to be fairly low.
All right. Expanding our analysis and looking at total animals imported from BSE countries, and these include the animals from the United Kingdom we just talked about.
The United States received an estimated 1,671 animals. Canada received just over 600, and here is the number breakdown. One important thing is some of these imports from Europe and Ireland are thought to be low risk. That accounts for about 500, 300, and then from other BSE countries, mostly European countries, Japan, of this total we got 800. Canada got 47.
So, again, you can see that there is potential here, and we don't know how much.
Okay. Now, shifting over to the next potential pathway, feed meal imports since the 1980s from the U.K., a total of approximately 81 tons. Here at the numbers per year. USA imported, again, about 10,500 metric tons of animal meat byproducts from BSE countries during 1980 to 2000.
So, again, potential pathways by which infectivity could have been introduced. Canada reported no meat and bone meal import since 1980, but there were imports of, of course, 8,500 metric tons of flours, et cetera, from these BSE countries, and I think other countries in Europe as well.
So, again, just looking over this, again, there is a potential. It's highly uncertain, especially for feed, figuring out what the probability of that feed will actually cause the disease, although we know that it is an efficient vector for transmitting the disease.
The next slide.
So now we get to the question about the U.S. and Canada and what's coming across the border. So we looked at cattle and beef, and what was coming across the border for each country. So considerable movement of animals and feed ingredients and beef products across the border, and I'm going to show you those data in a moment.
Trade and production practices, actually this should just be production practices, are very similar for each country. In fact, many of the companies collocate both in Canada and the U.S. So there are operations in both countries.
And there is an exchange, definitely, of animals between those companies, and then it's just important to remember from this that import or export, again, as I mentioned before, can be a mechanism by which to introduce or spread infected animals or contaminated products.
The next slide.
So these are data showing cattle trade in North America. We're going by U.S. cattle imports and exports, and what this shows is that here's the one million mark. We're basically importing in from Canada a significant number of animals. In 2002 it was about 1.6, 1.7 million animals coming in. Again, far fewer animals going out and being exported to Canada.
So we're actually importing a fair number of animals into this country from Canada.
The next slide.
And just to show you beef imports and exports, again, the red is Canada. Imports have been increasing into this country, about 350,000 metric tons, actually 370,000 metric tons came in in 2002, while about 60 or 70,000 tons was exported to Canada from the United States.
So, again, a big disparity between products, and especially food products coming in. Canada is by large shipping much more of its product to us than we are to them. So a tremendous change, and actually if you look at that, this is one mechanism by which we're actually accepting -- I mean, these aren't high risk products, most of them, but if they were, we'd be accepting that risk from Canada as well. They would be accepting some risk from us as well.
The next slide.
So conclusions in Part 1. Now, this is a qualitative assessment that I use to answer the question. It's really difficult to estimate absolute risk for U.S. and Canada. Again, it's very difficult to predict how many of those animals that came in could have been infected, and the feed as well. You know, when did it come in and was it infected? Did it contain infected material or not?
It's very difficult to note that with any sort of confidence. And again, and now as we sit here almost 15 years or more after those events happened because many of these animals and products were introduced into the U.S. prior to 1990, you've had all of this time for these numerous chance events to occur in the production system, and that means animals might have been rendered. They might have been rendered properly, not rendered properly. Feed might have been fed; infected feed might not have been fed feed. An infected cow might have died on the farm; it may not have died on the farm. It may have been in the system, et cetera.
Let's see. So I think just in conclusion, basically, considering the size of the production systems just from looking at what was brought into the country, both countries, imports with live animals and feed materials occurred since 1980 but was relatively small. A qualitative estimate that we would use would say that the risk that we would predict from this is that the risk would be low, but again, it's difficult to estimate with any uncertainty. So we're giving it this qualitative: we think the risk is low.
Let's go on to the second part. Okay. The second part, we're looking more at the human side of the equation, and I think Josh and the Harvard Center for Risk Analysis have done a really nice job of looking at animal production and then what goes into beef, but I think into the beef production cycle, but the issue with that is it just sort of stops there, and so this is somewhat of an extension of that work. It's like, who's eating what? We're trying to begin to estimate who's eating what and how much people are eating of these risk materials to get a better estimate of the risk.
Again, many potential routes for human exposure to beef and bovine products. Now, the primary source of potential BSE exposure in this country or in any country is probably through the food supply, mainly through consuming these high risk tissues. Again, these two account for about 90 percent of the total infectivity in a cow, and then eyes and dorsal root ganglia and small intestines have somewhat less infectivity.
Other sources include dietary supplements though, and those should be considered, and then medical products as well, devices, biologics, and drugs, and you're going to hear more about those tomorrow.
And I should emphasize that what we've got is sort of a narrow focus here on some of the higher-risk products. So what we're trying to do is estimate risk for some of the higher risk products, but what we then need to do is take those estimates and sort of slowly work out and look at the risk, for instance, for the other products. For instance, we need to include dietary supplements in our risk estimates because those are responsible for exposure, and then eventually the risk for medical products, which are probably lower in many cases.
So we need to have a more sort of holistic picture, and what we're trying to do is get a start on that by looking at the larger items responsible for risk.
The next slide.
All right. I always think it's interesting to talk about some of these products that people eat because organ meats and the types of things that are consumed are very unusual.
So we looked at BSE exposure pathways for the U.S. population by beef products, and we're looking in the first instance. We divided it into two things. We divided it into bovine brain or potentially spinal cord, but mostly focused on bovine brain, and what this is is consumption of potentially large amounts of high risk tissue, but people don't consume brain very frequently. So there are certain populations in the United States that do consume it, but for the general population, it's a pretty rare event.
You can go into a French restaurant and get calf brains, and I've seen cow brain sandwiches in some restaurants in the Midwest. So there are opportunities, but pretty low risk.
And then the second type of food product that could offer a potential risk is consumption of small amounts of these high risk tissues in processed foods. So mainly what we're concerned about is the advanced meat recovery product in this case, and those would include advanced meat recovery, is in many products.
For instance, ground beef products can contain some beef sausages, hot dogs, processed meat sauces, et cetera. So it's in many types of foods, types of beef products, beef foods.
Let's go to the next slide.
So looking just at our overall risk, I took this as a start to start looking at this year and what the risk is for this year, and we need to also expand these calculations out to prior years and then move them forward as well, but we started with 2003 because we have a fair amount of information to offer predictions.
So one positive animal identified out of 35 million slaughtered. So we know at least that we have a one in 35 million probability at the low end, and I have to -- Josh corrected me on this. It's 3.5 times ten to the negative seven. It's probably about an order of magnitude lower than I represented here. That's not going to affect the calculations though, but I'll show you in a minute, but you're going to see this number repeated, and just remember that it's about three times ten to the negative eight.
We accepted that as a lower boundary for our risk estimate. As a higher boundary, I actually just looked at what USDA was doing, and their estimate was they were looking at about a risk of one in one million in detecting their animals. I took that, actually, as a higher end. So if we have 35 million animals slaughtered per year, as our worst case scenario we assumed that potentially 35 animals could enter the food supply.
Again, it's an estimate. It's the same that Josh is doing. Basically, he stocked his with ten, 20, 100 animals. I'm stocking mine with one or 35 animals to do my analysis.
The next slide.
All right. So, to focus just on brain consumption for a moment, we've looked at the consumption databases that we have access to that are produced by USDA, and from that -- and we looked at a few other sources, too.
We're estimating right now the brain is rarely consumed by Americans, about 100,000 to 180,000 servings. So this is about half of a percent of all the brains at most that are produced of the cows that are slaughtered. So I think it represents about half a percent, no more than one percent.
And I think one thing to remember, the databases don't distinguish between calf brains from low risk animals versus high risk animals. We know there are cow brains that are being sold in the marketplace, too. So those aren't distinguished. So we're just making a worst case assumption that those are high risk for this purpose.
The probability of an infected brain then, we assume that people would eat about -- that those servings was a whole brain, a worst case shot. But the risk of that would be one in 35 million to one in one million of the eating an infected brain potentially.
And, again, your sample, only a very small percentage of people are eating this food. So, again, the risk would be very small that somebody would happen to get a brain that was infected, given the low prevalence of this disease, the low incidence in this country.
But I think it's important to indicate that the quantity of exposure would be pretty high, about 5,000 to 6,500, a conservative estimate for the cattle oral ID-50s that they might consume. That's a pretty big hit, and it's still unclear whether that would cause an infection in a person or not.
Again, a person would have to be susceptible to the agent as well. Remember the methionine homozygous at codon 129. So presumably 40 percent of the population would be susceptible to infection if they ate that much material possibly. Again, but that's highly uncertain.
So what we did, our conclusions from this are there is a risk of exposure via this route, but the risk to the U.S. general population, the larger population, is very low.
So let's move on to the next slide to get into advanced meat recovery. Now, this is sort of the flip side of the coin where we had a low probability of consuming high infectivity. We're at the flip side of that. We have a very -- sorry. My mouth is kind of dry.
So for the brain we have a low probability of consuming -- yeah, I think I'll actually take a glass of water.
So with brain we have a low probability of consuming perhaps a high infectious dose of material, and with AMR, we have a higher probability, although not extremely high, of consuming very low amounts of infectious material if the disease is present in an AMR process.
So just to remind people what AMR processing is, it's advanced meat recovery. It removes remaining meat from carcasses, the vertebral column and bone using machinery, and I think it's important to remember the spinal cord is usually removed before this process, but the dorsal root ganglia can serve as a source of infectivity because you can't remove that very easily from the vertebral column.
And I think about 70 percent to 80 percent of carcasses annually are processed annually with AMR as an estimate. That comes from a study commissioned by the USDA by the Sparks Company, and I think the one important thing about AMR is that when I look at this process, this is a process that really would mix and dilute the residual BSE agent that's present.
So you might imagine that there's residue in the spinal canal where the cord was where it is removed. There might be a little residual material there, and then there would be the dorsal root ganglia potentially that could serve as the sort of depot for any residual BSE agent if that animal was, indeed, infected.
The next slide.
Again, just continuing on, machines based on the Sparks study, again, machines can process 4,500 to 7,000 pounds of bones an hour. We estimated that this represents material from 20 to more than 35 animals. I think the high end of that estimate we still need to work on a little bit.
And from each animal you get approximately five to ten pounds of meat recovered per carcass. Again, we're being conservative on our estimate here. These are somewhat high, but actually within the realm of reason.
We estimated, and then based on a GAO study estimate as well, that approximately as much as 250 million pounds of AMR meat are produced annually. We also estimated on the low side of this, too. I think we went down to about 100 million to 250 million pounds because the estimates are very variable in the literature.
So the next slide.
So probability of exposure to advanced meat recovery product which is consumed frequently. Dilution of BSE, now there is this, again, as I mentioned before, there is this dilution of BSE infectivity through the batch of AMR product. So what you've got is you can imagine this machine that's moving these cow bones around and material is coming off. There might be water, brushes, artificial fingers, et cetera, artificial rubber projections, pulling meat off of these bones.