Animals > Animal Diseases > Bovine Spongiform Encephalopathy  

Risk Assessment on Bovine Spongiform Encephalopathy in Cattle in Canada

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December 2002

EXECUTIVE SUMMARY

Bovine spongiform encephalopathy (BSE) is a fatal neurological disease of cattle, with a long incubation period (average five to six years) and no existing test to detect disease in the live animal. Effective BSE prevention and/or effective control involves an evaluation of risk factors, implementation of appropriate risk management measures based on the outcome of the risk factor evaluation and an effective surveillance program.

In order to evaluate the risk for BSE in Canada, the Canadian Food Inspection Agency (CFIA) has carried out a risk assessment on BSE in cattle in Canada, which is presented in three companion reports. Part A is an evaluation of risk factors for BSE in Canada, Part B describes BSE surveillance in Canada, and Part C is a risk estimation for BSE in Canada.

PART A: EVALUATION OF RISK FACTORS

The Government of Canada is committed to safeguarding the Canadian food supply and preventing the entry and establishment of foreign diseases such as BSE, and Canada has committed significant resources to this end. It has a highly effective veterinary infrastructure, and the national Animal Health Program has implemented mandatory controls and surveillance consistent with or in excess of relevant international standards to ensure the continued exclusion of BSE.

Canadian import policies are considered to be highly effective in preventing the entry of BSE. Canada imports ruminants and ruminant products only from countries it has assessed and designated as free of BSE. A Feed Ban prohibiting the feeding of mammalian protein to ruminants (with exceptions) has been in effect since 1997. Under the feed ban, procedures must be in place to prevent cross-contamination of feeds, prohibited feed must be labelled so that it will not be fed to ruminants, and distribution records of feed and feed ingredients must be maintained.

One case of BSE was diagnosed in Canada in 1993, in a cow imported from the United Kingdom. The Canadian response was comprehensive, with the elimination from Canada of the herd, all offspring and all remaining animals imported from the U.K. Appropriate mitigating measures have been put in place in accordance with the most current scientific information.

Imports

• Import policies are consistently based on and continuously adjusted to consider the most current scientific information available and are designed to prevent the importation of contaminated materials and BSE-infected ruminants.
• The CFIA conducts risk assessments based on standards established by the Office International des Épizooties (OIE) to designate countries free of BSE. Livestock and specified livestock products may only be imported from countries designated free of BSE.
• Prior to the implementation of import policies specific for BSE, Canada’s conservative import policies for animals and animal products (designed to prevent the introduction of foot-and-mouth disease and other list A diseases) reduced the probability of BSE entry.

Slaughter

• In Canada, 95% of animals are slaughtered under federal inspection, including the majority of mature cows and bulls, and are therefore subject to ante-mortem inspection by CFIA veterinarians. Some 85% of cattle are slaughtered at a young age, when they would be unlikely to have developed BSE even if the agent were present in Canada. An estimated 4% of the total slaughter consists of mature dairy cows, the population of greatest concern.

Rendering

• All rendering plants are inspected annually, and compliance with the feed ban has been found to be very high.
• The structure of the rendering industry helps to mitigate risk. There are only 32 rendering facilities. Many are corporately owned, and more than half have dedicated production of either prohibited or non-prohibited material. Of the 13 that produce both prohibited and non-prohibited material, 9 use dedicated lines. The remaining 4 plants are required to have processes in place to reduce the risk of cross-contamination.
• Given the controls in place for BSE (e.g. import policies, the Feed Ban) and the lack of evidence that BSE is present in native Canadian cattle, the CFIA does not exclude specific risk material from rendering.

Feeds

• North America produces an abundant supply of economically priced grains and protein of vegetable origin. There is significant movement of feed ingredients between the U.S. and Canada, including significant quantities of rendered animal protein. Only highly processed micro-ingredients are sourced in any quantity from countries outside North America.

• The Feed Ban is considered to be effective at feed mills, based on inspections to date. A few deficiencies related to improper record-keeping have been corrected. Procedures to reduce the likelihood of cross-contamination are in place at all feed mills handling both prohibited and non-prohibited feeds. At the feed retail and farm level, compliance with the Feed Ban is based on random inspections combined with awareness and education programs.

• There are about 600 feed mills, which produce about 50% of the complete feeds used by Canadian farms. Currently, there is a trend towards dedication of facilities to handle either prohibited or non-prohibited feeds. Thirty-five percent of feed is produced in HACCP-certified mills. Seventy percent of the total annual commercial feed production is produced by 11 large feed corporations (169 feed mills). Fifty percent of the rendered animal protein used in livestock feeds is imported from the U.S.

• Ninety percent of the feed mill companies are members of a national organization that was involved in the development of the Feed Ban regulations, and there is a high level of awareness on the part of feed mill operators.

• Husbandry and feeding practices contribute to risk mitigation on-farm. Beef cattle, which make up 75% of the Canadian cattle population, are not generally fed meat-and-bone meal (MBM). High-producing dairy cattle are more likely to receive protein supplements containing MBM.

• Fifty percent of complete feeds are mixed on farm (for all species). About 80% of beef feedlots mix their own feed. The percentage of dairy farms mixing their own complete feed is unknown.

• About 4% of commercial cattle farms raise multiple species (pork and/or poultry), the only group in which potential for cross-contamination or errors in feeding exists. The percentage of the cattle population raised on multi-species farms is small.

PART B: BSE SURVEILLANCE AND RELATED ACTIVITIES

The BSE Surveillance Program in Canada is based on internationally recognized risk factors and pathways, in accordance with current international standards. It is developed and delivered through the collaboration of federal and provincial governments and universities. BSE surveillance programs continue to be revised and updated to ensure that they are based on the most current scientific information. In addition, education and awareness programs as well as effective compensation and cattle identification programs are in place to support the surveillance program.

A BSE surveillance program has been in place in since 1992, with samples including mature cattle exhibiting signs of neurologic disease from abattoirs and provincial and university laboratories, rabies-negative cattle, neurologic cases submitted to veterinary diagnostic laboratories and universities (tested since January 1991), non-ambulatory cattle (downer cattle/fallen stock) and emergency slaughter cattle. As of January 2002, 7,214 brains have been examined for BSE, and no evidence of the disease has been detected in native cattle by histopathology or immunohistochemistry.

Canada has consistently exceeded annual OIE standards for BSE surveillance since 1993, with one exception in 1995.

PART C: RISK ESTIMATION

The estimated probability of at least one infection of BSE occurring prior to 1997 was 7.3 x 10^-3 and therefore the likelihood of establishment of BSE in Canada was negligible. The risk was even further reduced by the mitigating measures in place since 1997.

In conclusion, the measures applied prior to the 1997 Feed Ban (import policies, disease control measures, detection system on-farm and at slaughter plants) combined with Canadian feed production and feeding practices, were effective in preventing the entry of BSE and its subsequent amplification through the feed system.