BSE – a wolf in sheep's clothing? Matthew Baylis, Fiona Houston, Rowland R. Kao, Angela R. McLean, Nora Hunter and Mike B. Gravenor Trends in Microbiology 2002, 10:563-570 The entire sheep flock in the UK has been threatened with slaughter if BSE is found in farmed sheep, largely on the grounds that an epidemic of BSE in sheep could be harder to contain than was the case for cattle, and that lamb could present a greater risk to consumers than beef. However, identifying BSE in a sheep is not straightforward, because of its similarities to the related disease, scrapie. Here, we review the likelihood that any UK sheep have BSE, how they might have got it, how a case could be identified and what the Government is doing in terms of surveillance and possible control methods.   In September 2001, the UK government published its contingency plan should naturally occurring BSE be found in sheep [1]. The contingency plan considers, as a worst-case scenario, slaughtering the entire national flock, with possible catastrophic impact on the livelihoods of tens of thousands of farmers and others involved directly or indirectly with the sheep meat industry. It would also change the face of the British landscape. By contrast, despite the fact that there were >1300 cases of BSE in UK cattle in 2001 and >100 people have died from variant Creutzfeld–Jacob disease (vCJD), probably following the dietary consumption of the BSE agent [2,3] , the culling policy for cattle has been selective, restricted to BSE-affected animals, their offspring and other cattle exposed to the same source of infection. The relative economics of cattle versus sheep have probably contributed to the difference in the policies for cattle and sheep BSE but the different nature of the diseases and the absence of precise data on sheep BSE have played an even greater part. Encouragingly, sheep themselves could have an alternative solution encoded in their genes, and the UK government is earnestly pursuing this possibility by instigating a policy of selective breeding for resistance. Cause for concern There have been no proven or even putative cases of BSE identified in farmed sheep. To date, all known cases of the disease have been induced under laboratory conditions by the experimental infection of sheep with tissue from infected animals ( Fig. 1). Nevertheless, there are reasonable grounds for believing that up to several thousand farmed sheep could have been infected with BSE and some could even have developed the disease but were overlooked. The recycling of ruminant tissue into meat and bone meal (MBM) in the 1980s, which was commonly fed to cattle as an ingredient of feed concentrates, is clearly linked to the development of the epidemic of BSE in cattle ( Box 1). Sheep, mostly adult pregnant ewes, are also fed concentrates, and these could also have contained MBM in the 1980s [4]. However, the amount of infectious material consumed by sheep would have been much less than that consumed by cattle. A sheep eats, on average, only 1–2% of the volume of feed concentrate eaten by a bovine [5] and the amount of MBM in sheep concentrate was at most equal to, and probably much less than, that present in the cattle equivalent [6]. Sheep, then, were much less exposed to BSE than were cattle.   Go to the Full Article > >  As a BioMedNet member you have free full-text access to this article within BioMedNet Reviews for 14 days  You will have full-text access to all articles if your institute subscribes. Recommend a subscription to your librarian  There are 15,000 more Review articles in BioMedNet Reviews  Please send us your feedback on this magazine		BioMedNet Magazine 18th December 2002 - 14th January 2003 Magazine Home Email to a Friend Full Article PDF printer ready version     Related Links in BioMedNet Reviews Journal Table of Contents Table of Contents by email Related Full Text Articles Browse Microbiology Browse Biochemistry Browse Genetics Search BioMedNet Reviews