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REPORT ON THE INVESTIGATION OF THE FOURTEENTH CASE OF BOVINE SPONGIFORM ENCEPHALOPATHY (BSE) IN CANADA

BACKGROUND

On July 25, 2008 a commercial beef cow in Northern Alberta was sampled by a private practitioner under Canada's National BSE Surveillance Program. Brain samples from this animal were sent to the Alberta Agriculture and Rural Development (ARD) laboratory where they were screened for BSE using a Bio-Rad rapid test on August 6, 2008. The result of this preliminary test did not rule out BSE. In accordance with the prescribed testing protocol, the test was repeated and produced a reaction a second time. Brain samples were then sent to the National BSE Reference Laboratory in Lethbridge, Alberta. Additional rapid tests for BSE (Prionics-Check PrioStrip and BioRad TeSeE ELISA) were conducted at the National BSE Reference Laboratory to validate the result of the screening test and were positive on August 12, 2008. The Prionics-Check Western and the Hybrid Western Blot was positive on August 14, 2008. Bovine Spongiform Encephalopathy was confirmed on August 14, 2008 using the Scrapie Associated Fibril Immunoblot procedure. The carcass was secured at the sampling site. 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 2008) of the World Organisation for Animal Health, referred to as 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 a commercial beef cow, Gelbvieh cross, born on March 20, 2002 and it was 76 months of age at the time of death. The animal was born, raised and had spent its entire life on the same farm. The producer reported the duration of illness as approximately 6 months with the animal exhibiting gradual deterioration culminating in the animal becoming non-ambulatory (downer). During this period, the animal showed a change in behaviour resulting in the animal becoming apprehensive/nervous. When examined by a private practitioner on July 25, 2008, the animal was recumbent. Physical examination by the practitioner revealed opisthotonus (muscle spasms). The practitioner and producer determined that the animal should be euthanized . A post-mortem examination was conducted, and the kidneys were observed to be smaller than normal with a thickened adherent capsule. A presumptive diagnosis of chronic renal disease was made by the submitting practitioner. Since the inclusion criteria of Canada's National BSE Surveillance Program were met, arrangements were made to forward appropriate samples for laboratory evaluation.

The birth farm was a commercial beef cow-calf operation. The birth cohort was determined to comprise 72 animals, which along with the case animal, were raised on the farm. Due to the practice of animals being sold in lots from the case premises, 106 animals (including the 72 birth cohorts) were traced. The trace-out investigation of the birth cohort located 6 live animals on the case farm and 3 live animals on a subsequent premises. All of these animals have since been humanely destroyed; their carcasses disposed of by incineration in accordance with the OIE recommendations. The following is the disposition of the remaining animals in the 97 animals:

  • 80 animals were traced and confirmed to have died or been slaughtered,
  • 14 animals were traced and presumed to have died or been slaughtered,
  • 3 animals were determined to be untraceable because of records limitations.

FEED INVESTIGATION

The feed investigation yielded limited records specific to the animal's first year of life. All feed products to which the BSE case animal had access were intended for feeding to ruminants.

Routine feeding practices were to provide animals with pasture during the summer months and to provide additional hay and grain during the winter. It was not farm practice to supplement the diets with commercially prepared rations, however due to drought conditions during the animal's first year of life, three commercially prepared rations were provided in addition to the commonly fed forages, grains, salt and minerals.

For the first seven months of life, the case animal was housed in a cow-calf pen and had pasture access. During this period, the animal received cow's milk and calf starter and had access to loose mineral, salt blocks and pasture. Beyond seven months to the end of the first year of life, the animal was housed in a calf pen where it received a creep feed, feedlot starter and possibly grain and straw and had access to salt blocks.

The three commercial rations made available to the BSE case animal consisted of a calf starter, a creep feed and a feedlot starter which were manufactured by two different commercial feed manufacturers.

Two forms of salt were used on farm: salt blocks and loose mineral salt. The salt blocks were manufactured by a company which does not handle any prohibited material. The loose mineral salt was manufactured by one of the same facilities which manufactured two of the commercially prepared rations received by the farm.

Neither of the two commercial feed manufacturers has production records dating back to the period of interest. As a result, trace back inspections at the manufacturers of commercial feeds distributed to the birth farm did not yield mixing formulas for the period of interest. As this was subsequent to the implementation of the 1997 Mammalian Feed Ban, it is very unlikely that ruminant meat and bone meal was intentionally used in the formulation of any of the three commercially prepared rations or loose mineral salt distributed to the birth farm.

However, as production records are not available for review, it is not possible to rule out that contamination during production could have taken place. One of the two commercial feed manufacturers did handle ruminant meat and bone meal (prohibited material/PM), however they did have procedures in place to prevent the contamination of ruminant feed with PM. The other commercial feed manufacturer did not handle PM directly, though they did receive a premix used in the manufacture of one of the feeds received by the case farm, from another facility which did handle PM.

INVESTIGATION OVERVIEW

The detection of this case does not change any of Canada's 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 (including non-ambulatory animals). This effort is directed at determining the level of BSE in Canada, while monitoring the effectiveness of the risk-mitigating measures in place. Canada's National BSE Surveillance Program continues to demonstrate an extremely low level of BSE in Canada, with 14 positive animals detected.

With respect to BSE, the safety of beef produced in Canada is assured by public health measures enacted 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 is effectively preventing the amplification of BSE in Canada's feed system. Additional regulations to enhance Canada's feed ban were enacted in 2007. The most important change is the removal of SRM from all animal feeds, pet food and fertilizer. The enhancement will accelerate progress toward eradicating BSE from the national cattle herd by preventing more than 99 per cent 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.