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U.S. Department of Health and Human Services

Animal & Veterinary

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Epidemiology of Campylobacter in Humans

Kirk Smith, D.V.M., Ph.D.

DR. SMITH: Thank you. And good morning. This is kind of a daunting task to cover this topic in ten minutes. So bear with me if I speed through some things.

(Slide.)

Well, Campylobacter is the most commonly recognized cause of bacterial gastroenteritis in the United States. It is estimated that there are about two million symptomatic infections per year which is a figure you will see in the risk assessment. And this corresponds to roughly one percent of the United States population.

The most commonly identified species of Campylobacter among clinical isolates from humans is C. jejuni which accounts for 95 to 99 percent of the isolates. Most of the rest are Campylobacter coli which is clinically indistinguishable. So when you talk about the epidemiology of human Campylobacter infections, we are talking primarily about C. jejuni.

(Slide.)

Campylobacter jejuni is found worldwide. As in the United States, it is very common in other industrialized countries. It is actually hyper-endemic in developing countries. And most children will experience multiple infections by the time are a few years of age. And so it is not common that Campylobacter is a commonly identified cause of traveler's diarrhea.

(Slide.)

We will get more into the clinical signs and symptoms later. But Campylobacter causes diarrhea, often with fever and cramps and often with bloody stools. The incubation period can range anywhere from one to eight days. But it is typically three to four days. It is usually a self-limited illness. But it can cause serious invasive illness, particularly in the elderly, infants and the immunocompromised.

(Slide.)

Just to mention FoodNet briefly. Some of you I am sure are familiar with it. It is a collaborative agreement between these federal agencies and certain state health departments.

(Slide.)

And these are the FoodNet sites currently that cover a population of about 20 million people.

(Slide.)

And FoodNet does active surveillance for a number of bacterial pathogens including Campylobacter. And it does surveillance for parasitic organisms, syndromes related to food-borne disease and also food-borne disease outbreaks.

(Slide.)

Well, based on FoodNet data, again, Campylobacter is the most commonly recognized bacterial cause of gastroenteritis among the FoodNet sites. And you can see it is consistently so each year.

(Slide.)

And this graph shows the seasonality of Campylobacter infections in this country. And typically what you will see is a marked upswing in cases during May or June and then a peak in July and August and a steady decrease throughout the rest of the year.

(Slide.)

And this graph is Minnesota data, just a little different way of showing the same thing, the summer seasonality of Campylobacter infections.

(Slide.)

Well, this graph shows the age distribution of Campylobacter cases. By far the highest incidence is in infants where we will see an incidence of greater than 50 cases per 100,000 people. Children less than five years of ago also suffer a fairly high incidence, not really demarcated on this graph.

We see a second peak in incidence amongst young adults 20 to 30 years of age and to a lesser extent 30 to 40 years of age.

(Slide.)

Well, almost all human Campylobacter infections are accounted for by these sources, poultry, unpasteurized milk, inadequately treated surface water, pets and foreign travel. The specific sources of infection during foreign travel aren't really known, but are very likely to be the other sources on this list.

(Slide.)

Well, poultry is by far the most important source of Campylobacter for humans. In most surveys, you will find that 50 to 80 percent of retail products are contaminated. And poultry accounts for roughly 50 to 70 percent of sporadic human infections with Campylobacter. And this is a figure that you would also see in the risk assessment.

In evidence from throughout the world including some work we have done in Minnesota, it is apparently that poultry is a source for fluoroquinolone-resistant Campylobacter for humans, as well.

(Slide.)

This table shows outbreaks of Campylobacter that have occurred in the United States from 1978 to 1996. And first let me say that outbreaks due to Campylobacter are rare. You can see an average of about six per year in the whole country. And when they do occur, you can see they are food-borne or water-borne. The specific source for many of the food-borne ones is actually unpasteurized milk.

You can see poultry isn't implicated specifically in many outbreaks, but many of the other food items that are linked to the outbreaks have actually been cross-contaminated with poultry in the kitchen.

(Slide.)

The seasonality of outbreaks due to Campylobacter is different than the seasonality of sporadic cases. Again, sporadic cases, seasonality in the summer outbreaks. The seasonality tends to be in the spring and in the fall. And this is due to largely to the seasonality in outbreaks due to unpasteurized milk shown in yellow and due to inadequately treated water in blue.

(Slide.)

Okay. So just a brief summary. Summer seasonality. Sporadic cases are -- account for the vast majority of cases, are far more common than outbreak-associated cases. Sporadic cases occur for 99 percent of all Campylobacter cases.

Poultry is the primary source of Campylobacter for humans in the sporadic cases at least. And person-to-person transmission of this organism is rare. For some reason, we -- it just doesn't appear to be very efficient. We don't see the institutional outbreaks. We don't see the day care outbreaks that we do with some other pathogens such as Shigella and E. coli 0157:H7.

(Slide.)

Okay. Back to clinical features. Infection with Campylobacter can range from no signs whatsoever, it can be asymptomatic, or it can cause death. Diarrhea is a hallmark, of course, and it is often severe, often producing bloody stools. Fever can occur. Abdominal pain, severe abdominal pain is another hallmark of Campylobacter infection. And the nausea and malaise occur commonly, as well.

(Slide.)

Now, Campylobacter gastroenteritis is usually self-limiting. The duration is usually less than a week, although it is a pretty miserable existence for a week. It is a debilitating illness.

The duration can be up to three weeks in 20 percent of cases. Systemic infections are rare. Most isolates are from stool. Only about 0.5 percent of isolates are from blood. And the hospitalization rate for confirmed Campylobacter infections is about ten percent, ten or 11 percent. And that is really a fairly high figure when you think about it.

(Slide.)

The case fatality ratio from a couple of outbreaks is three to 24 per 10,000 cases. And it is estimated that there are 100 to 150 deaths per year in the United States. And Campylobacter not only causes gastroenteritis, but it does cause some chronic sequelae including reactive arthritis and Guillain Baret syndrome.

(Slide.)

So antibiotic treatment for Campylobacter gastroenteritis is not needed in most cases. It is beneficial to patients with prolonged or worsening symptoms, high fevers or bloody stools. And it is definitely indicated for patients who are immunocompromised or pregnant. This is very important. Our immunocompromised population is going to do nothing but grow as the baby boomers age.

(Slide.)

So the drugs of choice for Campylobacter when treatment is indicated are either erythromycin or a fluoroquinolone such as Ciprofloxacin. And fluoroquinolones are used widely for the empiric treatment of gram negative bacterial enteritis. And it is also a treatment of choice for traveler's diarrhea.

And so where as both will work fine on Campylobacter, erythromycin actually is not effective for the other causes of bacterial gastroenteritis. And that is what causes a problem for physicians, is Campylobacter needs to be treated early. And so treatment needs to be started before culture results are back.

(Slide.)

Just quickly, a little bit about NARMS on the human side. Just quickly, Ciprofloxacin resistance was documented in 13 percent of Campylobacter infections both in 1997 and '98.

(Slide.)

I just quickly want to tell -- this is the work that we had published in May. I do have reprints of this article for anybody that is interested in catching me during the next two days. But quickly, in that we show -- and these are the data -- the data from 1998 are what is in the paper. These are the percentage of Campylobacter isolates submitted to the Minnesota Department of Health that were resistant to quinolones.

In red are the yearly figures. In blue are the quarterly figures. In 1998 -- that is as far as we got published, the yearly data, the yearly percentage resistant was ten percent. In 1999, now, of course that is not counting December yet, but things won't change much. But not counting December, the yearly percentage resistant is over 17 percent now.

And you can see during the first quarter, 39 percent of isolates were resistant. And even during the trough in the third quarter of this year, over ten percent of isolates were resistant.

(Slide.)

And this is in the paper, so I won't belabor it. But we did show a clinical effect. Quinolone resistance did result in a longer duration of illness for patients that were treated with quinolones.

(Slide.)

And we did isolate Ciprofloxacin-resistant Campylobacter from poultry and -- quite commonly and showed identical DNA fingerprints in resistant isolates from chickens and domestically acquired resistant human cases.

(Slide.)

Okay. And that is my whirlwind tour. And I will stop there. Thank you.

(Applause.)

DR. BEAULIEU: Maybe one question for Dr. Smith. Tom?

(Away from microphone.)

MR. : Yes, I was curious to see if your number graphics supplied --- less --- evidence --- particular segment of the population --- Campylobacter?

DR. SMITH: Well, absolutely. I really don't think a lot of it comes directly from eating raw or undercooked poultry. I think most people know not to eat undercooked chicken.

What I think is happening is I think the vast majority of Campylobacter infections from poultry actually comes from cross-contamination in the kitchen of other food items, food preparation surfaces, utensils and so on and so forth. So that would be my best guest.

DR. BEAULIEU: Thank you. Our next speaker is Dr. Paula Cray. Dr. Cray has a whole series of degrees associated with microbiology, bacteriology, biochemistry, veterinary microbiology. She is currently the Research Leader of the Antimicrobial Resistance Research Unit at USDA's Agricultural Research Service at the Russell Research Center in Athens, Georgia.

She has a great deal of experience dealing with food-borne pathogens, particularly Salmonella and Campylobacter. And she indicates that one of her other interests is she is also proficient in fast foods. And she and Dr. Sundlof might want to compare notes there because I know he is an expert at McDonald's.