ARCHIVED - Report on the Investigation of the Seventeenth Case of Bovine Spongiform Encephalopathy (BSE) in Canada

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Background

On February 12, 2010, the Alberta Provincial Laboratory informed the CFIA Edmonton District Office of a BSE Surveillance sample (collected through the Canada Alberta BSE Surveillance Program) with a reaction on the BIO-RAD TeSeE ELISA rapid test that did not rule-out BSE.

Samples were forwarded to the National and OIE (World Organisation for Animal Health) BSE Reference Laboratory in Lethbridge, Alberta. The samples were confirmed as BSE positive using the immunohistochemistry (IHC) procedure on February 25, 2010. In addition to the IHC procedure, the National BSE Reference Laboratory evaluated the sample using the Prionics-Check Western® rapid test, Hybrid Western Blot, the Prionics Check PrioSTRIP® rapid test, BioRad TeSeE ELISA and the Scrapie Associated Fibril Immunoblot (SAF immunoblot). All test results were determined to be positive. Western blot results indicate the case was c-type (classical) BSE.

The carcass was secured at the sampling site and transferred to Canadian Food Inspection Agency's (CFIA) laboratory in Lethbridge for incineration. No part of the carcass entered the human food supply or animal feed chain.

The CFIA immediately initiated an epidemiological investigation based on the recommended BSE guidelines (Terrestrial Animal Health Code 2010) of the OIE. Specifically, the CFIA followed the recommended BSE guidelines for a country with controlled risk status and investigated:

  • the feed cohort, comprising all cattle which, during their first year of life, were reared with the BSE case during its first year of life, and which investigation showed consumed the same potentially contaminated feed during that period, or
  • the birth cohort, comprising all cattle born in the same herd as, and within 12 months of the birth of the BSE case, if the above cannot be identified and
  • feed to which the animal may have been exposed early in its life.

Animal Investigation

The positive animal was confirmed to be a commercial beef cow born on March 22, 2004, therefore being 71 months of age at the time of death. The animal was born, raised and had spent its entire life on its birth farm. The positive animal was reported by the owner to have been non-ambulatory (downer) in the days preceding its death. No treatments had been given and the animal subsequently died on February 5, 2010. After consultation with the local veterinary practitioner it was determined that the animal met the inclusion criteria of Canada's National BSE Surveillance Program. Accordingly, arrangements were made to collect and submit appropriate samples for evaluation.

The index farm is a cow-calf operation with both purebred and commercial beef cattle. The birth and feed cohort was determined to comprise 630 animals.

The trace-out investigation located 73 live animals on 3 premises including the index farm. All of these animals have been placed under quarantine. To date, 19 of the 73 live cohorts have been humanely destroyed and 4 cohorts died from natural causes. Twelve of the carcasses have been disposed of by incineration and 11 carcasses at an SRM approved landfill in accordance with OIE recommendations. The remaining cohorts are permanently identified, their movements controlled and will be destroyed or upon their death their carcasses disposed of in accordance with OIE recommendations.

The following is the disposition of the other animals in the birth/feed cohort:

  • 119 animals were traced and confirmed to have died or been slaughtered;
  • 288 animals were traced and presumed to have died or been slaughtered;
  • 95 animals were traced and confirmed to have been exported for slaughter and the importing country has been notified
  • 46 animals were determined to be untraceable because of records limitations
  • 9 animals were subsequently ruled out as equivalent risk animals

Feed Investigation

The feed investigation focused on feeds to which the case animal may have had access during its first year of life and on the manufacturing practices used to produce these feeds. All feed products to which the BSE case animal was known to have had access were intended for feeding to ruminants. These consisted of farm-grown forages and grains, commercially prepared mill-run wheat pellets from a single supplier, and mixed feed products from five other commercial suppliers.

Feeding Practices

Calving occurs annually, in March. During the first four months of life, the case animal would have been fed its mother's milk and creep feed and had access to hay, grain, pelleted cow ration, free choice minerals and salt. No milk replacers were used.

In June, cow-calf pairs were moved to pasture where they stayed until December. During this period, the case animal would have had access to free choice minerals and salt, plus small amounts of grain. The animals may have also had access to wheat mill-run pellets. In December the calves were weaned and fed rolled grain and hay, free choice minerals and salt, until the following March. In addition, it is probable that these calves also had access to pelleted cow and calf rations and wheat mill-run pellets during the winter period.

Feed Sources

Investigation of the facility which was the sole supplier of the wheat mill-run pellets identified that this was a specialized single ingredient feed manufacturing facility which never handled or used prohibited material. Therefore this product was ruled out as a possible source of contamination.

The supplier of the minerals and premixes used on the farm is now out of business. Investigation results from previous BSE investigations confirmed that this facility did not use or handle prohibited material during the time period under review for the current case. Therefore these products were ruled out as a possible source of contamination.

Investigation at a commercial feed mill which provided two medicated complete feeds to the farm during the case animal's first year of life identified that this facility did not use or handle prohibited material. Mineral premix and vitamin premix products used as ingredients in these feeds were traced back to a specialized premix facility which never used or handled prohibited material. These products are therefore ruled out as a possible source of contamination.

Investigation at a commercial feed mill which supplied one non-medicated creep feed identified that this facility did not use prohibited material. Therefore this product was ruled out as a possible source of contamination.

A commercial feed mill which was identified as providing several complete feeds for cows, calves and bulls to the case farm between September 2003 and June 2004 is no longer in business. This facility is known to have used prohibited materials during the time period of interest. It is not possible to rule out that contamination of these products during production or transport could have taken place.

Investigation at a commercial feed mill known to have provided several medicated and non-medicated feeds including creep, calf and cow rations, determined that the facility did use prohibited material during the time of interest. This facility had procedures in place for handling and using prohibited materials. However, some production records for products manufactured between November 2004 and March 2005 were not available and, consequently, it is not possible to rule out that contamination of these products during their production could have taken place. Review of records associated with a creep feed produced by this facility revealed an incomplete clean out of a truck unloading mechanism between delivery of a hog feed containing prohibited material and the creep feed which was subsequently delivered to the case farm. Record review allowed the remaining products supplied by this facility to be ruled out as a possible source of contamination.

Investigation Overview

The detection of this case does not change any of Canada's identified BSE risk parameters. The location and age of the animal are consistent with previous cases. Surveillance results to date, including this case, reflect an extremely low level of BSE in Canada.

Since the confirmation of BSE in a native-born animal in May 2003, Canada has significantly increased its targeted testing of cattle in high-risk categories advocated by the OIE. This effort is directed at determining the level of BSE in Canada while monitoring the effectiveness of the risk-mitigating measures in place.

With respect to BSE, the safety of beef produced in Canada is assured by public health measures further enhanced in 2003. The removal of specific risk material (SRM) - the tissues that have been demonstrated to have the potential to harbour BSE infectivity - from all animals slaughtered for human consumption is the most effective single measure to protect consumers in Canada and importing countries from exposure to BSE infectivity in meat products.

As demonstrated by the surveillance system, the feed ban implemented in 1997 has effectively prevented the amplification of BSE in Canada. Additional regulations to enhance Canada's feed ban were enacted in 2007. The most important change was the removal of SRM from all animal feeds, pet food and fertilizer to avoid potential cross contamination. The enhancement will accelerate progress toward eradicating BSE from the national cattle herd by preventing more than 99 percent of potential BSE infectivity from entering the Canadian feed system. These measures are effectively minimizing the risk of BSE transmission.

Canada is officially categorized under the OIE's science-based system as a controlled BSE risk country. This status clearly recognizes the effectiveness of Canada's surveillance, mitigation and eradication measures, and acknowledges the work done by all levels of government, the cattle industry, veterinarians and ranchers to effectively manage and eventually eradicate BSE in Canada.

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