Animals > Animal Diseases > Transmissible Spongiform Encephalopathies  

Transmissible Spongiform Encephalopathies (TSEs)

QUESTIONS AND ANSWERS

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 mule deer, white tail deer and elk.

There are no live animal tests, no treatments and no vaccines for these diseases.

Creutzfeldt-Jakob Disease (CJD) is a rare and fatal form of TSE that affects humans worldwide. A newly recognized 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.

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 are different theories about the origin of this disease including the possibility that BSE occurred at undetectable levels in British cattle prior to 1986. Many experts believe that BSE in England may have been caused by feeding 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. Changes in the rendering process (the elimination of the solvent-extraction process and of second steam-heat treatment) in the early 1980's may have allowed the protein to remain active in rendered material.

Scrapie in sheep 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 in elk and deer is a relatively new disease. It was first identified in 1967 in deer at research facilities in Colorado. Scientists have not been able to identify the cause of CWD or its mode of transmission. It has been suggested that infected deer and elk may transmit the disease through animal-to-animal contact, and through contamination of feed or water sources with saliva or feces.

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.

Through Canada’s BSE surveillance program there have been 3 cases of BSE found in Canada since 2003. The first case of BSE was reported May 20, 2003. The animal was condemned at slaughter and no meat from the carcass entered the food system. The CFIA responded with a comprehensive investigation that tested some 2,000 animals. All test results were negative for BSE.

The second and third cases were confirmed on January 2 and 11, 2005, respectively. Neither of these animals entered the food or feed systems. Investigations into these 2 cases are currently underway.

BSE has been a reportable disease in Canada since 1990.

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 province of Saskatchewan and Alberta. It was first diagnosed 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. Research into CWD, its transmission, and diagnosis are ongoing to increase our knowledge of the disease and its distribution within Canada.

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

A newly recognized form of CJD, variant Creutzfeldt-Jakob disease (vCJD), was first reported in March 1996 in the UK. Cases of vCJD diagnosed in people living in the UK and France are thought to be linked to the consumption of meat products derived from BSE-infected cattle.

There is no evidence that scrapie or CWD can be transmitted to humans or cattle. CWD is not BSE, although public concern has been generated by some media reports referring to CWD as "mad elk disease."

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, animal biologics, and the livestock feed program. The CFIA has the legislative authority to impose quarantine measures and to require the 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.

BSE:

Canada made BSE a reportable disease in 1990. As a reportable disease, any suspect BSE case must be reported to a CFIA veterinarian immediately. The purpose of the CFIA BSE policies is to prevent its entry and establishment. Canada only allows the importation of live ruminants and their meat and meat products from countries assessed by Canada as free of BSE. Other animal products are assessed on a case-by-case basis and may be permitted entry if judged not to present a risk of introducing BSE.

Because BSE is believed to be transmitted via feeding rendered ruminant products (such as processed meat and bonemeal) to ruminants, the prevention of such animal feed practices is a key part of Canada’s program for the prevention of BSE. Canada has not imported ruminant-derived meat and bone meal for livestock food from the UK during the last decade. In 1997, the CFIA banned the feeding of all rendered products obtained from ruminants such as cattle, sheep, goats, bison, elk or deer, to ruminants. In December 2000, the CFIA suspended the importation of rendered animal protein of any species from any country that is not recognized as free of BSE.

Domestic surveillance for BSE has been ongoing since 1991. The national BSE surveillance program is based on testing brain tissue submitted to federal, provincial and university laboratories.

Scrapie:

In 1945, Canada made scrapie a reportable disease. The current control and eradication program for scrapie is based on the detection of clinical cases of scrapie, laboratory confirmation and destruction of affected sheep or goats, other ‘at risk’ animals (which may include the whole flock), and either incineration or burial of the carcasses. Other regulatory approaches such as active surveillance and flock certification are currently under development.

CWD:

In April 2001, CWD was made a reportable disease and a national program to eradicate CWD has been in place since the fall of 2000. The program is based on the rapid detection of clinical cases, laboratory confirmation and destruction of affected elk and other ‘at risk’ animals (which may include the whole herd), and either incineration or burial of the carcasses. Other regulatory approaches such as active surveillance, herd certification, and licensing of all cervid farms are being considered in co-operation with Health Canada, the provinces and industry. Velvet from animals known to be infected with CWD is destroyed under CFIA control.

What is Canada doing to prevent diseased animals and their products from entering the food supply?

To prevent infected animals from entering the commercial food supply, sheep infected with scrapie, elk and deer infected with CWD, and other ‘at risk’ animals (which may include the whole herd), cannot be sent to abattoirs or rendering plants. The animals are humanely destroyed and are either buried or incinerated. Products from infected animals such as antler velvet are also either incinerated or buried.

What other steps is Canada taking to control the spread of TSEs?

Animal products, including food and animal feeds, are freely traded between the United States and Canada. Thus, many of the risk factors are similar for both countries. Accordingly, Canada is working closely with the United States (and Mexico) to harmonize TSE policies.

There is a constant evolution in scientific and trade information on TSEs, particularly BSE. The CFIA is constantly reviewing and refining its policies and diagnostic methods. Significant scientific research is under way in Canada, but more research will be required to identify the most efficient and effective approaches to the management of risks associated with BSE, scrapie, and CWD.

Does the CFIA allow the importation of processed foods derived from beef such as bouillon, soups, and stock cubes from Europe?

Processed foods such as bouillon, soups, and stock cubes that contain a negligible meat content (i.e. less than 2% of rendered fat and meat extract in the ready-to-serve product after added water) are exempt from the Meat Inspection Regulations.

Other products such as salad dressing, dairy-base dip, flavouring, seasoning preparations and cheeses containing 3% or less of meat ingredients are not considered meat products for the purpose of the Meat Inspection Regulations.

These products are not subject to CFIA meat import controls and can be imported from any country.

Are we at risk by eating beef and dairy products?

Canadian beef and dairy products are safe for consumption. All ruminant products that are known to pose a risk of BSE are banned from entering Canada. There are exempt products that are not considered to be a risk for the transmission of BSE. These include milk and milk products, hides and skins, gelatin, collagen, and protein-free tallow and its derivatives.

There are no import restrictions for gelatin from any country for industrial and laboratory use, human consumption, pharmaceuticals, and pet food. These products are cleared by Canada Border Services Agency. The CFIA has import requirements for gelatin brought into Canada for livestock and poultry food. Gelatin-based products for human use and consumption are regulated under the Food and Drugs Act and Regulations.

Is it safe to eat beef products (canned meat, TV dinners) processed in other countries?

Beef products can be imported from countries that are not BSE-free (such as Italy) provided the beef has been imported from a BSE-free country (such as New Zealand) and further processed (e.g., by canning) in a CFIA-approved processing plant. Product thus processed presents no greater BSE risk than meat imported from a BSE-free country. Pork products are not subject to BSE-related restrictions, but must be processed in CFIA-approved plants.

What about the link between vCJD and BSE?

The Public Health Agency of Canada (PHAC) is the Federal department responsible for evaluating diseases that threaten the health of Canadians. PHAC has formed a science team with participation from CFIA to conduct a risk assessment on the human health implications of BSE. The results of this risk assessment may make it necessary to adjust BSE policies accordingly. Information on TSEs is also available by visiting PHAC’s Website.

Where can I get more information on TSEs?

A comprehensive report entitled " The Bovine Spongiform Encephalopathy Inquiry" is available on their Web site.

Other suggested sites are:

• World Health Organization (the international authority on human health)
• Office international des épizooties
• Chronic Wasting Disease Alliance

November 2005