Bovine Spongiform Encephalopathy

Scientists believe that BSE is most often spread through the practice of feeding cattle various meats (rendered material) from slaughtered animals such as sheep, goats, and other cattle.

During this process, an abnormal protein that is linked to BSE can spread from a slaughtered diseased animal to a healthy one. This abnormal protein, called a prion, can withstand high temperatures and does not get destroyed during the rendering procedure. Since the incubation period for BSE is so long, it is possible for an infected animal to enter the food chain before the symptoms appear.

Proteins are long molecules that are folded up into particular shapes. A prion is folded differently from a normal protein, and it can cause normal proteins to change and fold abnormally. When this happens, the proteins (normally found in liquid form in cells) begin to solidify.

The cells most often infected are the brain cells. The resulting solidification of the proteins causes the infected brain tissues to look like a sponge with several tiny holes, hence the name "spongiform encephalopathy."

Because BSE damages the brain tissue, it has a variety of symptoms ranging from behavioural changes to coordination problems. Cows with BSE may show nervousness or aggressive behaviour, difficulty with coordination, trouble standing up, decreased milk production, and weight loss. The disease is fatal, with death usually occurring 2 weeks to 6 months after symptoms start.

sCJD usually occrs in older patients with an average age of 67, but it has been reported in teenagers and people in their 90s. It is fatal after only a few months. vCJD usually occurs in younger patients and lasts about one and a half years.

Live animals cannot be tested for the disease. The only way to confirm the presence of BSE is by checking the brain tissue of an animal after it dies. Upon examination, the brain is found to be full of small holes, like a sponge.

In humans, a genetic test exists to determine if a person might be susceptible to vCJD, but again, the only way to confirm the diagnosis is through a sample of brain tissue obtained through a biopsy or autopsy.

There is no cure, treatment, or vaccine for BSE, CJD, or vCJD.

The best way to prevent the disease is to avoid feeding cattle rendered material from slaughtered animals, and to isolate and destroy all infected animals. Most countries have developed policies for monitoring BSE in their cattle herds and procedures for dealing promptly and thoroughly with BSE cases when they do arise.

Canada is continuing to work to prevent and control BSE:

• Health Canada works closely with the Canadian Food Inspection Agency (CFIA) as part of the agency's National Response Team.
• The CFIA has taken various precautions to prevent the introduction and spread of BSE, including creating a surveillance program in which the brains of cattle are tested for the disease.
• The CFIA has mandated that all suspected BSE cases be reported to a federal veterinarian. The CFIA has also created a Canadian Cattle Identification Program for cattle and bison, making it possible to trace individual animal movements from the herd of origin to the time of slaughter.
• In 1997, Canada banned the feeding of rendered protein products from ruminant animals (cattle, sheep, goats, bison, elk, or deer) to other ruminants.
• In 2007, Canada implemented an enhanced BSE-related feed ban. This regulation extends the original feeding ban to all animal feeds, pet food, and fertilizer products.
• A permit issued by the CFIA is now required for those needing to handle, transport, or dispose of cattle carcasses and certain cattle tissues.
• More detailed policies regarding the prevention and control of BSE are available on the Health Canada website.

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