What is Bovine Spongiform Encephalopathy ?
Bovine Spongiform Encephalopathy (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 (CJD) 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.
Why does BSE have such a high profile?
British scientists have suggested that a newly recognized form of CJD, known as variant Creutzfeldt-Jakob disease (vCJD), found in Britain in recent years, may be caused by human exposure to BSE. People afflicted with this strain of the disease tend to be from a younger portion of the population than those with classical CJD. BSE has gained a high profile as a result.
Do we have BSE in Canada?
There have only been two cases of BSE ever diagnosed in this country. The first case was found in 1993 in a beef cow that had been imported from Britain in 1987. The animal carcass and the herd it came from were destroyed and additional measures were taken immediately by the federal government to deal with any risk that Canadian cattle might have been affected. The second case of BSE was reported May 20, 2003. The animal was condemned at slaughter so no meat from the carcass entered the food system. the Canadian Food Inspection Agency (CFIA) responded with a comprehensive investigation that tested some 2000 animals. All test results were negative for BSE. BSE has been a reportable disease in Canada since 1990.
Symptoms/Signs of BSE
BSE is an unusual disease in that the time between an animal’s exposure to the disease and the on set of clinical signs ranges from three to six years.
Animals with BSE may show a number of different symptoms including nervous or aggressive behaviour, abnormal posture, lack of co-ordination or difficulty 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 20 years ago 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 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 the potentially contaminated material from the food chain. as a result, since the winter of 1992-1993, the number of BSE cases in Great Britain has been progressively dropping. In addition, other possible methods of transmission are still being scientifically investigate.
Diagnosis of BSE
There is no test do 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.
What is being done to prevent BSE from entering and becoming established in Canada?
Canada, as well as many other countries, has taken precautions to prevent the introduction and spread of BSE. These measures include the following:
- The creation of a surveillance program in which the brains of cattle are tested for the disease.
- Since 1997, Canada has banned the feeding of rendered protein products from ruminant animals (cattle, sheep, goats, bison, elk or deer) to other ruminants.
making BSE a reportable disease, such that any case of BSE must be reported to a federal veterinarian.
- The creation of a Canadian Cattle Identification Program for cattle and bison, making it possible to trace individual animal movements from the herd to origin of slaughter.
- Controlling the importation of products that are assessed to have a high risk of introducing BSE into Canada. Canada only allows the importation of live ruminants and their meat and meat products from countries that Canada considers to be free of BSE. Canada also has additional import controls for animal products and by-products from countries that have confirmed BSE in native animals. Their animal products are assessed on a case-by-case basis and may be permitted entry if they are judged not to present a risk of introducing BSE.
- Canada has not imported ruminant-derived meat and bone meal for the purpose of livestock feeding from Europe for more than a decade. In December 2000, the CFIA suspended the importation of rendered animal material of any species from any country that Canada did not recognize as free of BSE.
- Canada requires the removal of certain cattle tissues, known as specified risk materials, at slaughter. Specified risk materials are tissues that, in BSE-infected cattle, contain the agent that may transmit the disease. In diseased animals, the infective agent is concentrated in certain tissues such as the brain and spinal cord.
What can cattle and dairy producers do?
If you notice an animal is showing any signs of the symptoms of BSE, contact your veterinarian, or notify the local CFIA district office, which is listed in the blue government pages of the phonebook.
Check your feedbags carefully for the label “do not feed to cattle, sheep, deer or other ruminants.” Such feed contains material prohibited for ruminants.
If you mix feed on your farm, make sure that you do not mix feeds for non-ruminants (such as horses, swine or poultry, etc.) with any feed for ruminants.
If you have both ruminants and non-ruminants on your farm, or if you mix your own feeds on your farm, keep all invoices for feeds.
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