Bovine spongiform encephalopathy (BSE): the end of the beginning or the beginning of the end?

Abstract

Bovine spongiform encephalopathy (BSE) is a zoonosis being the origin of variant Creutzfeldt-Jakob disease and an important cattle disease in its own right. This association has driven both the research into the disease and extensive epidemiological investigations of practical value. Not only has the occurrence of BSE has a serious effect on animal health and public health, it has also seriously interrupted trade in cattle and cattle products from affected countries. Since 2001, several additional European countries, Japan, Israel and Canada have reported BSE in native-born stock and this has led to a concern about the BSE status of countries that have imported cattle and cattle products from any affected country. A single case recently reported in the USA was in a cow imported from Canada, thus extending the risk of BSE occurrence into the North American continent as a whole. Extensive feed and offal bans have protected the food and feed chains in all countries with BSE, even though initially they tended to be leaky. Application of newly-developed, approved 'Rapid' tests for misfolded PrP in central nervous tissue of targeted, high-risk animals and slaughter cattle now provides the tools whereby the real incidence of the disease (and to a degree, infection) can be determined in an active surveillance programme. 'Rapid' testing also enables the progress of epidemics to be monitored in response to applied measures. In the EU, over 10 million cattle are tested annually. Analysis of the extensive data shows that it is the beginning of the end of the BSE epidemic in the UK; most European countries, Israel and Japan are close behind. The epidemic in North America (two cases to date) is at the beginning. Significant measures had already been adopted there to reduce the risk from recycling of infection via feed but it remains to be seen if they are watertight. Advice has been given to ensure that public health is protected and to monitor the epidemic by strategic use of approved 'Rapid' tests to determine that the epidemic is in fact trivial as believed, or otherwise to identify weaknesses in measures that can be corrected. It is imperative that all countries conduct risk assessments for BSE, follow the OIE recommendations and do not unreasonably disrupt international trade. There is a responsibility for all countries with BSE to ensure that infection is not exported to any country, particularly through live cattle and especially via meat-and-bone-meal, which is the acknowledged vehicle of transmission. There is also a responsibility placed upon all countries to protect, not only their cattle populations, but also their human populations from exposure to this economically important fatal disease. If all the advice is taken and measures enforced there is a prospect that BSE can be eliminated from countries and regions as a prelude to eradication from the world.