Bovine Spongiform Encephalopa... Health Article

CONTROL OF BSE

To stop the continued spread of BSE, three principle strategies are used: surveillance, preventing the exposure of ruminants (cattle, sheep, and goats) to feed made from ruminant protein, and slaughter of diseased animals. Because of the long incubation period for BSE (four to five years), cases have continued to be reported after the implementation of these measures. The peak of the epidemic was seen in 1992, at which point the UK was reporting over 30,000 cases of BSE per year.

Cases of BSE reported after the feed ban was implemented are known as "born-after-ban" (BAB) cases, and investigation of them revealed important holes in safety measures. BAB cases appear to be the result of an incomplete application of the feed ban and an incomplete understanding of the importance of even a small amount of contamination—a piece of brain tissue the size of a peppercorn is sufficient to infect a bovine animal. In the UK, feed bans had to be extended (in 1994) to include all mammalian protein in ruminant feeds, with a further extension in 1996 to prevent the use of mammalian MBM in all animal feed. Cross-contamination of tissues in slaughterhouses, feed mills, and other sites also required management. Furthermore, inspection, animal tracing systems, financial incentives, and fines were implemented to ensure that all risk materials were removed from carcasses and that animals with disease were reported and destroyed.

The European Union did not introduce its feed ban legislation (a simple ruminant-to-ruminant feed ban) until 1994, by which point it was too late to prevent the introduction of the disease. When the first human cases of vCJD occurred in 1996, the UK was prohibited from exporting bovine meat, cattle, and bovine-based products. As recently as November 2000, with the recognition of more than expected numbers of cases of BSE, it became clear to the EU that their interventions had been both inadequate and inadequately enforced. Measures to prohibit all animal protein feed to farm animals were to be introduced in the EU within 2001. However, the extent of spread of the epidemic among national herds will not be visible for a number of years.

At the international level, a question exists regarding non-European countries who also imported implicated MBM from the UK and Europe. Few non-EU countries have surveillance system for BSE, yet many nations imported and used implicated MBM, and many also imported live cattle. The risk that the disease has been imported into these countries without the financial capacity to enact the required interventions could result in a new foci of distribution of this devastating disease. International guidelines, such as those promulgated by the Office International des Epizooties, the Food and Agriculture Organization, and the World Health Organization are only partial solutions. It is clear that risk analysis must be conducted in each country in order to assess the risk that BSE was imported and whether the conditions exist for its further propagation.

MAURA N. RICKETTS

(SEE ALSO: Transmissible Spongiform Encephalopathy; Veterinary Public Health; Zoonoses)

BIBLIOGRAPHY

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WEB SITES OF INTEREST

For information about BSE reports: http://www.OIE.int.

For WHO consultations and opinions: http://www.who.int/emc/diseases/bse/index.html.

For information concerning EU decisions: http://europa.eu.int/comm/food/index_en.html.

Web site of the CJD Surveillance Unit (with connections to UK ministries and international surveillance systems sites): http://www.cjd.ed.ac.uk/index.htm.