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Sheep and BSE

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Transmissible Spongiform Encephalopathies (TSEs)
These are a group of diseases that affect the central nervous system. These diseases are fatal and are characterized by spongy degeneration of the brain. Bovine spongiform encephalopathy (BSE), which affects cattle and is commonly referred to as "mad cow disease", belongs to the TSE group of diseases. Scrapie is a TSE that affects sheep and goats. Chronic wasting disease (CWD) is a TSE that affects cervids such as mule deer, white tail deer and elk. 

What is BSE?
 Bovine Spongiform Encephalopathy (BSE) affects the central nervous system of beef and dairy cattle. It is also sometimes referred to as "mad cow disease".BSE belongs to the family of diseases known as Transmissible Spongiform Encephalopathies (TSEs). Other diseases in this family include chronic wasting disease in deer and elk, scrapie in sheep, and Creutzfeldt-Jakob Disease in humans. Although the origin of these diseases is unknown, they are caused by the presence of an abnormal protein in the brain called a prion.

It is believed that cattle contract BSE through meat and bone meal (MBM) containing the remains of other cattle infected with the disease. It is also possible that mothers can pass the disease to their offspring, however, this theory has not been confirmed. BSE is not transmitted from cattle to cattle.

BSE and Scrapie
During the BSE outbreak in the United Kingdom in the late 1980s, it was speculated that cattle contracted BSE from feed containing sheep offal infected with scrapie. Scientific evidence, however, did not validate this theory, and therefore, the theory was discarded. Although BSE contaminated feeds can pose a risk to sheep, there is no risk of scrapie being spread to cattle or humans.

BSE and the Sheep Industry
Following the announcement on May 20th, 2003 that BSE was discovered in a cow in Alberta, the United States closed its border to all Canadian ruminant and ruminant products, including sheep. Since December 2003, Canada has closed it's border to American sheep following the discovery of BSE in a dairy cow in Washington state. The dairy cow was further proven to originate from Canada.

Can Sheep get BSE?
In Britain, to date, not a single case of naturally occurring BSE has been found in British sheep. However, it is possible that the disease could be in the British flock and that its presence is being masked by the more widespread problem of scrapie.

Experiments have shown that it is possible to infect sheep with BSE by feeding or injecting them with brain tissue from cattle infected by BSE. There is the chance that sheep could have eaten infected animal feed and contracted the disease. However, sheep do not live as long as cattle and any sheep that may have eaten contaminated feed, before it was banned from all livestock feed in the UK in August 1996, will have already died.

There are 40 million sheep in the UK and 5,000-10,000 of them are estimated to contract scrapie each year. Since 1998, any sheep confirmed to have scrapie in this country have been compulsorily slaughtered as a precautionary measure. This means that, even though scrapie does not appear to pose a health risk to humans, these animals do not enter the human food chain.

Government agriculture experts are working on a scheme to breed sheep that have a built in genetic resistance to scrapie and other TSEs. However, it will take at least 10 years for such a breeding program to have a significant effect and longer for the problem to be eradicated.

Agriculture Canada's latest news and information about BSE in Canada.

Web links that give background information from Europe on BSE and Sheep, or, why Agriculture Canada and the USA now ban sheep imports from each others country.