What is mad cow disease? Quick facts about BSE

mad cow disease
A case of mad cow disease has been confirmed in a beef cow from Alberta. THE CANADIAN PRESS/Jeff McIntosh

CALGARY – BSE is back in the spotlight in Canada with another confirmed case in Alberta. Here’s what you need to know about how the disease is spread, its potential danger to people and the steps Canada takes to prevent BSE-infected cattle from entering the human food chain.

What is “mad cow” disease?

Bovine Spongiform Encephalopathy (BSE), is a fatal, neurological disease of cattle. While the exact cause of the disease isn’t known, it is linked to rogue proteins called prions. The disease causes microscopic holes in the brains of affected animals, giving tissue a sponge-like appearance. There is no treatment or vaccine currently available for the disease, according to the World Organization for Animal Health. BSE is related to chronic wasting disease in elk and deer, and scrapie in sheep.

How is BSE spread?

BSE is spread through cattle feed that contains ground meat and bone meal from an infected cow. The original source of BSE is believed to have been feed containing tainted meat from sheep with scrapie. The disease gets into the human food supply when an infected cow is slaughtered for meat. Milk from infected cows doesn’t spread the disease, according to the Canadian Food Inspection Agency. Canada banned animal-based feed in 1997.

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How is BSE diagnosed?

There is no test to diagnose BSE in live animals. A tentative diagnosis may be made by observing certain symptoms in cattle including nervous or aggressive behaviour, trembling, lack of coordination and weight loss despite an increased appetite. The disease can only be confirmed by examining an animal’s brain after it dies.

What is the history of BSE in Canada?

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The first case of BSE in a Canadian-born beef cow was discovered in May, 2003. A sick cow from an Alberta ranch had been sent to a slaughterhouse but was removed because of its condition. The cow did not end up as food for people or other animals, although the carcass was sent to a processing plant for rendering into oil.

In the following weeks, several ranches in Alberta, Saskatchewan and British Columbia were quarantined as a precaution and 1,400 cows were  slaughtered. 
Borders were immediately slammed shut to all live Canadian cattle as well as meat-based products. The United States reopened its border to young Canadian cattle in 2005 but older cattle were barred until 2007. Canada’s last confirmed case of BSE was reported in February, 2011.

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Does BSE pose a danger to humans?

There is strong evidence to suggest that eating BSE-contaminated beef or meat-based products can lead to variant Creutzfeldt-Jakob disease (vCJD), according to the World Health Organization. It was first diagnosed in humans in 1996 in the United Kingdom, where BSE is believed to have originated.

Creutzfeld-Jakob in humans leads to psychiatric symptoms, immobility and eventually death. Canada’s first case was confirmed in 2002 and a second case was identified in 2011, according to the Public Health Agency of Canada. Both were believed to have been contracted abroad. No cases of vCJD have been linked to eating Canadian beef. Fewer than 250 cases have been reported worldwide; two in Canada, the majority in the United Kingdom and France.

What does Canada do to prevent BSE?

BSE has been a reportable disease in Canada since 1990. Canada accepts imports of cattle, beef or beef-based products only from counties that are considered to effectively control BSE. In 2007, the Canadian Food Inspection Agency banned the use of protein products from cattle, including the brain, spinal cord and intestine, from all animal feed, pet food and fertilizers.

Since there is no test to confirm BSE in live cattle, the brains of thousands of slaughtered cattle are routinely tested for the disease.

READ MORE: U.S. company recalls 4,012 pounds of beef products over mad cow concerns

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