Animal & Veterinary
THE SPREAD OF BSE IN SWITZERLAND-EPIDEMIOLOGY AND ONGOING ERADICATION OF A CHALLENGING DISEASE
by Lukas Perler, D.V.M
FDA Veterinarian Newsletter 2002 Volume XVI, No V
Twelve years ago, Switzerland was the first country on the European mainland to diagnose a case of Bovine Spongiform Encephalopathy (BSE) in an indigenous animal. Since then, the spread of this challenging disease has substantially influenced veterinary services and feed control officials. As a result of the ongoing eradication program the number of BSE cases is significantly decreasing and the situation improves gradually.
BSE was first diagnosed in the United Kingdom in 1986. In Switzerland, it was declared a notifiable animal disease in June 1988. The Swiss Federal Veterinary Office subsequently ensured that no further import licenses would be granted for meat and bone meal from Great Britain. In 1989, it started informing veterinarians about this new animal disease-of which there had been no recorded cases in Switzerland previously. Research on diagnostic methods and the epidemiology of BSE was specifically encouraged and from that point special attention was paid to central nervous system disorders in cattle.
In November 1990, the first case of BSE on the European mainland that could not be attributed to an animal imported from Great Britain was reported in Switzerland. Material originating from Britain was most probably given new origin labeling and then imported via an indirect route (third countries) to Switzerland. According to the Swiss foreign trade statistics only very small quantities of meat and bone meal were imported directly from Great Britain. Immediately after the first case, measures were taken, the most important being a ban on the use of risk organs for human consumption, implemented on November 8, 1990. On December 1, 1990, a ban on the feeding of mammalian meat and bone meal (MMBM) to ruminants went into effect.
The feed ban on MMBM to ruminants still represents the most important measure to prevent the spread of BSE within the cattle population. In Switzerland, the elimination of all organs that may possibly contain infectivity for BSE (mainly brain and spinal cord from cows) from the rendering process has contributed since May 1996, to further decrease the risk of BSE-transmission. As of January 2001, the feed ban of prohibited material to all farmed animals-total feed ban-has been implemented in Switzerland and the EU member countries.
The average age of the BSE-infected cattle in Switzerland at the time of their death is 5.3 years. The youngest animal was 32 months and the oldest 13 years old. Almost 50% of the affected animals were born after the introduction of the MMBM feed ban (Born after Ban cases). In Switzerland, there is no indication that vertical transmission occurred.
Up to 1994 the number of new reports of BSE in Switzerland had almost doubled each year. The peak was reached in 1995 with 68 cases. This number seems comparatively low in comparison to the annual peak of about 36,000 diagnosed cases in the United Kingdom in 1992. In 1996, as a result of the feed ban, a clear trend reversal was seen for the first time in Switzerland, and in 1998 a provisional minimum of 14 cases was recorded. After introduction of active BSE monitoring as part of the surveillance investigation program, the number of cases increased again. In 1999, 25 cows were identified as clinical BSE cases; another 25 infected cows were added to this number on the basis of the specific surveillance program. Since 2001, almost all animals over 30 months are tested for BSE at regular slaughter. Therefore, 42 BSE cases were detected last year. As of the end of July 2002, the number decreased significantly to 12 BSE cases for the ongoing year. Hopefully, this positive trend will continue as a result of the stringent eradication program in Switzerland.
Dr. Perler is a visiting veterinarian from the Federal Veterinary Office of Switzerland. He is a recognized expert on BSE.
FIGURE 1 BSE Cases Worldwide According to the Year of First Diagnosis
TOTAL WORLWIDE NUMBER OF BSE CASES UNTIL 07/05/2002
Czech Republic (2)
YEAR OF FIRST DIAGNOSIS
1986 - BSE in UK
1989 - Ireland
1990 - Portugal
1991 - France
1997 - Netherlands
1998 - Liechtenstein
2000 - Denmark
2001 - Italy
2001 - Poland
Worldwide Distribution of BSE
Geographical Distribution of Countries that Reported at least one BSE Confirmed Case from 1989 to 6 May 2002
(world map shown)
Map Legend: Dark shading indicates "Countries having reported BSE in indigineous animals"
Light shading indicates "Countries/territories having reported BSE in imported animals only"