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Fact Sheet - Bovine Spongiform Encephalopathy (BSE)

What is BSE?

BSE is a progressive, fatal disease of the nervous system of cattle. It is what is known as a transmissible spongiform encephalopathy (TSE). Other TSEs include scrapie in sheep, chronic wasting disease in deer and elk, and Creutzfeldt-Jakob disease in humans. Although the exact cause of BSE is unknown, it is associated with the presence of an abnormal protein called a prion. There is no treatment or vaccine currently available for the disease.

BSE in Canada

BSE has been a reportable disease in Canada since 1990.

In 1993 BSE was found in a beef cow that had been imported from Britain in 1987. The animal was destroyed and additional measures were taken immediately by the federal government to deal with any risk that Canadian cattle might have been affected.

Canada's first case of BSE in a domestic animal was found in May 2003.

Symptoms/Signs of BSE

BSE is an unusual disease in that the time between an animal's exposure to the disease and the onset of clinical signs normally ranges from four to five years. Animals with BSE may show a number of different symptoms including nervous or aggressive behaviour, abnormal posture, lack of co-ordination or difficulty in rising from a lying position, decreased milk production, and weight loss despite an increased appetite. These symptoms may last for a period of two to six months before the animal dies.

Transmission of BSE

Scientists believe that the spread of this disease in cattle in Great Britain was caused by feeding protein products made from infected cattle or sheep. This occurred in the late 1970s and early 1980s. It was then magnified by the practice of feeding rendered material from slaughtered cattle to other cattle. The protein that is linked to BSE is resistant to normal inactivation procedures such as heat, which means that it may not be completely destroyed in the rendering process and could remain active in rendered material. In 1988, Great Britain banned the use of this rendered material in animal feeds, thus removing potentially contaminated material from the food chain. As a result, since the winter of 1992-93, the number of BSE cases reported in Great Britain has been progressively dropping. In addition, other possible methods of transmission are still being scientifically investigated.

Diagnosis of BSE

There is no test to diagnose BSE in live animals, although a tentative diagnosis may be made based on clinical signs. Diagnosis can only be confirmed by microscopic examination of the animal's brain after its death.

How Does Canada protect food safety and animal health from BSE?

Canada, as well as many other countries, has taken precautions to prevent the introduction and spread of BSE. These measures include the following:

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