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Bovine spongiform encephalopathy

Bovine spongiform encephalopathy (BSE), also known as mad cow disease, is a prion disease that affects cattle. It is a progressive, fatal disease of the central nervous system (the brain and the spinal cord) of cattle. Learn how to recognize the disease, protect cattle and what we're doing to keep Canadians safe.

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Forms of the disease

There are 2 forms of BSE: classical and atypical.

Infographic – comparing atypical and classical BSE

The disease in Canada

The first case of BSE in Canada was detected in 1993, in a beef cow that had been imported from the United Kingdom in 1987. The first case of BSE in a Canadian-born cow was found in May 2003.

Scientists believe that the spread of classical BSE in cattle in the United Kingdom was caused by feeding cattle with protein products derived from animals unknowingly infected with BSE prions. This occurred in the late 1970s and early 1980s.

Confirmed cases and completed investigations

Current status

On May 27, 2021, the World Organisation for Animal Health's World Assembly of Delegates recognized Canada as a country with negligible risk for BSE.

Achieving "negligible risk" status for BSE does not trigger any immediate changes in Canada's current BSE control programs or requirements.

A comprehensive analysis must be completed before making any changes to Canada's BSE control programs, including verifying that any changes would not jeopardize Canada's new negligible BSE risk status or international markets.

Reporting the disease

BSE is a reportable disease under the Health of Animals Act, and has been since 1990.

This means that, by law, all animals infected or suspected of being infected with BSE must be reported to a Canadian Food Inspection Agency (CFIA) district veterinarian.

To report a suspected or known case of BSE, contact your local CFIA animal health office.

Signs of the disease

The time between an animal's exposure to BSE and the onset of clinical signs averages 4 to 5 years.

These signs may last for 2 to 6 months before the animal dies.


In infected cattle, the prion protein that is linked to BSE concentrates in certain tissues.

In the early stages of the disease, the prion protein is found in tissues related with the gut and associated lymph nodes. As the disease advances, the prion protein moves into the brain, eyes, tonsils, and spinal cord. These tissues are known as specified risk material (SRM).

Prions are resistant to normal inactivation procedures such as heat. This means that they may not be destroyed in the rendering process and could stay active in rendered material, such as feed.

Limiting spread

To limit the spread of BSE among cattle and protect animal health as well as public health:

Detailed measures are in place to avoid cross-contamination of edible beef products, animal feed products and fertilizer ingredients.

Transmission to humans

Evidence exists for an animal-to-human link between classical BSE and Variant Creutzfeldt-Jakob disease by consuming beef contaminated with BSE prions.


Although animals infected with BSE sometimes show signs, BSE can only be confirmed by testing brain tissues from an infected animal after it is dead.


No treatment or vaccine exists for BSE.

Protecting Canadian livestock from BSE

The government has taken measures to prevent the introduction and spread of BSE in Canada.

Canada's BSE safeguards

Read the overview of Canada's BSE safeguards, which include:

Safeguards that work together to limit the risks associated with BSE

Safeguard How it limits BSE risks
Import restrictions Prevents new infections from entering Canada
Feed bans Limits the spread of BSE and decreases the level of the disease present in Canada
Removing higher-risk tissues from all dead cattle Limits the spread of BSE

How cattle producers can help keep Canadians safe

Keeping food safe

Canada has taken steps to keep food safe.


All Canadian cattle that leave their farm of origin are tagged with a radiofrequency identification device (RFID). This helps tracking activities if a food safety issue occurs.

Tracing meat products

The Safe Food for Canadians Regulations requires that industry under federal inspection maintains a traceability system for all edible meat products if a recall is necessary.

Examining animals

Operators of abattoirs under federal inspection must, by law, evaluate each animal when it arrives at their facility in order to detect abnormal behaviour, physiology or appearance.

A CFIA inspector also inspects each animal to ensure that the ones showing potential signs of BSE have been appropriately identified and segregated until a CFIA veterinarian can examine them.

If the animal is not slaughtered within 24 hours of this examination, a new examination and inspection must be performed.

This is an important step, as one cannot detect any visible abnormalities that are characteristic of BSE in the carcass once the animal has been slaughtered.

What the operator is looking for

System Abnormal signs
Locomotor weakness, abnormal head carriage, lack of coordination, circling, changes in gait
Sensory kicking, blindness, head pressing, head shyness, hypersensitivity to light, touch and noise
Mental apprehension, change in behaviour, abnormal ear position, nervousness, apprehension about passing through entrances, teeth grinding, aggressive behaviour

If the CFIA veterinarian confirms that the animal presents signs, it will be condemned. It will not be permitted to proceed to the slaughter floor or to other areas of the establishment where edible products are being processed.

The animal will be isolated, humanely euthanized and then sampled for BSE.

Other steps to control food safety risks from BSE

Because an animal can carry BSE prions for years before showing signs, Canada requires that industry remove from the edible meat products any tissues that may carry prions. These are specified risk material (SRM).

There are also detailed measures in place to avoid cross-contamination with SRM, including carcass identification, dedicated tools and segregation measures.

The Guidance on specified risk material details the expectations in slaughter establishments under federal inspection to meet SRM removal requirements. A separate guidance is available for slaughter establishments under provincial/territorial jurisdiction.

Good manufacturing practices and hygienic measures are also regularly used to lower the risk of cross-contamination between products and from the slaughter environment.

Daily sanitation of the slaughter facility, ongoing sanitation and cleaning of tools and equipment, control of product flow, identification and segregation procedures are just a few principles implemented to mitigate contamination risks to meat products.

More information

For industry

Fact sheets

International activities and trade

Provincial/territorial information

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