Transmissible Spongiform Encephalopathies (TSEs)

What are TSEs?

TSEs are a group of diseases that affect the central nervous system. These diseases are fatal and are characterized by spongy degeneration of the brain. Bovine spongiform encephalopathy (BSE), which affects cattle and is commonly referred to as "mad cow disease", belongs to the TSE group of diseases. Scrapie is a TSE that affects sheep and goats. Chronic wasting disease (CWD) is a TSE that affects cervids such as white-tailed deer, mule deer, black-tailed deer, moose and elk..

Creutzfeldt-Jakob Disease (CJD) is a rare and fatal form of TSE that affects humans worldwide. A form of CJD called variant Creutzfeldt-Jakob disease (vCJD) has been diagnosed since 1996 and is thought to be linked to the consumption of meat products derived from BSE-infected cattle.

There are no treatments and no vaccines for these diseases.

How did these diseases come into existence?

The cause of these diseases is unknown, but infected individuals and animals produce abnormal proteins which are laboratory markers used in the detection of infection.

The true origin of BSE is still unknown. There is international consensus that BSE is spread by feeding infected ruminant (cattle, sheep, goats, deer, elk , bison) protein products to cattle. The protein that is linked to BSE is resistant to normal inactivation procedures such as heat.

Scrapie has been in existence for several hundred years. The disease is thought to spread most commonly from ewe to offspring and to other lambs in the same group through contact with the placenta and placental fluids.

CWD was first identified in 1967 in deer at research facilities in Colorado. Scientists believe that deer and elk transmit the disease through contact with feed and water contaminated by saliva or feces from infected animals.

Do these diseases exist in Canada?

In 1993 BSE was found in a beef cow that had been imported from Britain in 1987. The animal was destroyed and additional measures were taken immediately by the federal government to deal with any risk that Canadian cattle might have been affected.

Canada's first case of BSE in a domestic animal was found in May 2003. This case and all of the limited number of subsequent cases have been thoroughly investigated.

Scrapie occurs in countries all over the world. It occurs in Canada at a very low level and has been the target of a stringent control program since 1945.

CWD has been reported in the United States, and in the Canadian provinces of Saskatchewan and Alberta. It was first diagnosed in Canada in farmed elk in Saskatchewan in 1996. The disease is thought to have been introduced by elk imported from the United States in the late 1980s.

Can BSE, scrapie or CWD be transmitted to humans and other animals?

Variant Creutzfeldt-Jakob disease (vCJD), was first reported in March 1996 in the UK and is thought to be linked to the consumption of meat products derived from BSE-infected cattle.

There is currently no scientific evidence that scrapie or CWD can be transmitted to humans or cattle.

What is Canada doing to prevent the spread of TSEs?

The CFIA is responsible for implementing animal health and disease control programs. The key elements of these programs include:

  • Veterinary services
  • Disease surveillance
  • Laboratory-based diagnostic testing
  • Domestic and import controls
  • Food safety controls
  • Livestock feed program
  • Voluntary Scrapie Flock Certification Program
  • CWD Voluntary Herd Certification Program

The CFIA has the legislative authority to impose quarantine measures, and to order the humane destruction and disposal of animals or animal products suspected of disease infection. There is also a program to compensate owners for animals and animal products ordered destroyed.

For more information on Canada’s approach to controlling and eradicating TSEs, please see the individual fact sheets on BSE, scrapie, and CWD.

Where can I get more information on TSEs?

Suggested websites include:

Information on this page is from the Canadian Food Inspection Agency

Canada is continually assessing international scientific information as it becomes available and modifying policies as required, based on new information.

Comments (0) 05.11.2009. 16:31

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