Bovine spongiform encephalopathy

Bovine spongiform encephalopathy (BSE), also known as mad cow disease, is a prion disease that affects cattle. This disease gets worse over time and eventually causes death, affecting the central nervous system (the brain and the spinal cord) of cattle. Learn about the disease, how to protect cattle and what we are doing to keep Canadians safe.

On this page

Forms of the disease

There are 2 forms of BSE: classical and atypical.

  • Classical BSE is caused when cattle are fed protein products that come from other cattle, which may carry BSE prions
    This practice has been banned in Canada since 1997 to stop the spread of the disease.
  • Atypical BSE is rare and happens by chance in old cattle
    It is not believed to spread between animals.

Infographic – comparing atypical and classical BSE

The disease in Canada

  • Canada's first case of BSE was found in 1993 in a beef cow imported from the United Kingdom in 1987
  • The first case in a Canadian-born cow was found in May 2003
  • The most recent case of classical BSE in Canada was in 2015 in a bovine born in 2009
  • The latest case of atypical BSE was detected in 2021
  • In the late 1970s and early 1980s, classical BSE spread in cattle because they were fed cattle protein products from animals that unknowingly were infected with BSE prions

Confirmed cases and completed investigations

Current status

On May 27, 2021, the World Organisation for Animal Health (WOAH, formerly known as OIE) World Assembly of Delegates recognized Canada as a country with negligible risk for BSE. This recognition did not trigger any immediate changes in Canada's BSE control programs or requirements, as a thorough review must first be completed to ensure that any changes to programs will not affect Canada's negligible BSE risk status or access to international markets.

Detection and reporting of BSE

Since 1990, BSE has been a federally reportable disease under the Health of Animals Act. We have a National BSE Surveillance Program.

Transmission

In cattle with BSE, the prion protein associated with the disease builds up in specific tissues. In the early stages, it is found in the small intestine and nearby lymphatic tissues. As the disease gets worse, prions build up in the brain, eyes and spinal cord. These tissues are classified as specified risk material (SRM).

Prions cannot easily be destroyed by inactivation procedures such as heat treatments. This means that they might survive the rendering process and could stay active in rendered material, which is used as an ingredient in animal feed.

Limiting spread

We have measures to limit the spread of BSE and protect public and animal health.

  • In 1997, Canada banned feeding most mammal-based proteins, including SRM, to cattle and other ruminants
  • Since 2003, SRM has been removed from all cattle slaughtered for human consumption
  • Since 2007, feeding SRM to any animal (including pets) or using SRM in fertilizer has been banned
  • There are strict rules to prevent cross-contamination between beef products, animal feed and fertilizer ingredients

Transmission to humans

There is evidence that classical BSE can be linked to Creutzfeldt‑Jakob disease, a human disease variant that can be caused by eating beef contaminated with BSE prions.

Diagnosis

Although animals with BSE may show neurological clinical signs, the disease can be confirmed only by testing the brain tissue of the animal after it has died.

Treatment

No treatment or vaccine exists for BSE.

Protecting Canadian livestock from BSE

We have measures in place to prevent BSE from entering and spreading 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 Stops classical BSE from entering Canada by regulating bovines and their products being brought in from other countries.
Feed bans Prevents cattle from being fed products made from other cattle.
Removing higher-risk tissues from all dead cattle Ensures SRM from dead cattle are removed and that they cannot be turned into products that might contaminate cattle feed.

Ways that cattle producers can help keep Canadians safe

Keeping food safe

We have strict measures to keep food safe, thus ensuring that Canada meets international standards and keeps the risk of BSE in beef products very low. These measures include hygienically removing SRM during slaughter, banning certain stunning techniques to avoid contamination and ensuring that SRM do not enter the human food chain.

Traceability

All Canadian cattle are tagged with a radiofrequency identification device when leaving their farm of origin. This helps track them in case there is a food or feed safety issue.

Tracing meat products

Under the Safe Food for Canadians Regulations, businesses under federal inspection must have a system to trace all edible meat products in case they need to be recalled.

Examining animals

Operators of abattoirs under federal inspection are required by law to check each bovine when it arrives for signs of abnormal behaviour. A CFIA inspector also inspects all bovines to ensure that the ones showing potential signs of BSE are identified and kept apart until a CFIA veterinarian can examine them. This is an important step because BSE is not visible in a carcass once the animal has been slaughtered.

If the bovine presents neurological signs, it will not be allowed to the slaughter floor or to other areas where edible products are being processed. A bovine will be classified as a BSE surveillance candidate if it:

  • is at least 30 months old
  • was not imported into Canada
  • was the only animal in the group presenting signs

Candidates will be isolated, humanely euthanized and tested for BSE.

Other steps to control food and feed safety risks from BSE

To reduce the risk of BSE prion cross-contamination in cattle feed, Canada requires that SRM be removed from edible meat products. Strict measures are put in place to keep SRM from coming into contact with meat products. Specific measures to avoid cross-contamination with SRM include:

  • carcass identification
  • dedicated tools
  • segregation measures

We have Guidance on specified risk material that outlines federal inspection requirements for SRM removal in slaughterhouses. There are also guidelines detailing Inspection of specified risk material (SRM) controls in non-federally registered cattle abattoirs (abattoirs under provincial and territorial jurisdiction).

Good manufacturing practices and hygienic measures are regularly used to prevent and minimize cross‑contamination risks between products and the slaughter environment. These include:

  • daily cleaning of facilities
  • regular cleaning of tools and equipment
  • controlled product flow
  • clear procedures to identify and separate products

More information

Date modified: