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CFIA’s Investigation into the December 2003 Washington State BSE Case

by 5m Editor
22 March 2004, at 12:00am

CANADA - Following the diagnosis of BSE in Canada on May 20, 2003, the Canadian Food Inspection Agency (CFIA) launched a comprehensive and exhaustive investigation. Efforts included trace-back, trace-forward and feed investigations, which spanned four provinces and included some 2,700 animals.

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Introduction

The Canadian approach to the December 2003 BSE case in the United States (US) was similar in thoroughness. As we learned through our experience, the appropriate response to a case of BSE is a thorough and scientifically-based investigation.

Animal Investigation

The CFIA’s animal investigation was designed to address three main issues: determine the herd of origin of the BSE-positive cow (index case) found in Washington state (WA), if the index case originated in Canada, then trace her life history including her movement to the US, and identify other animals in the birth herd in Canada that may have had similar exposure to BSE.

Through the Health of Animals ear tag, herd and registration records, it was determined that the animal was born on April 9, 1997 on a farm in Alberta. The herd records identified the index case’s sire, dam and Canadian born calves. Neither the dam nor the Canadian born calves were located in Canada. The DNA of the brain of the index case, its hide (located by Canadian investigators working in Washington State with their U.S. counterparts), semen from its sire and DNA of one its offspring (born in the US) were compared. The results confirmed the identification of the animal.

Tracing of the index case's life history determined that it was part of a herd of 113 dairy animals that were dispersed as follows: 17 were moved in September of 2001, to multiple destinations, 1 went to auction, 3 were slaughtered for the owner’s use, 11 went to a dairy farm, and 81, including the index case, were exported in September, 2001 to a heifer breeding operation in WA. At the heifer breeding operation, 3 animals were kept, 8 animals were moved to a heifer raising operation in WA, and 70 animals, including the index case, were moved to Mabton, WA (the US Index Herd) where the case of BSE was found.

The disposition of the significant animals remaining in Canada is described in the section Depopulation of Canadian Cattle, below.

Feed Investigation

The CFIA’s feed investigation was designed to identify all feeds that the index case consumed and determine if any contained ruminant meat and bone meal. Feeding of ruminant meat and bone meal to ruminants is believed to be the most likely means of transmission of BSE. Regulations now prohibit this practice in Canada.

The CFIA’s on-farm investigation of the birth herd identified two feeds of interest, a dairy ration and a protein supplement.

Review of the CFIA’s feed mill inspection records indicated that the feed mill which produced the dairy ration had a good Health of Animals Act compliance history. The feed mill’s formulae showed that ruminant meat and bone meal was used in the ration until July 1997 and discontinued when the Canadian feed ban was implemented in August 1997.

It was highly unlikely that the protein supplement was the source of exposure, since it would probably have been consumed before the index case had access.

The feed investigation concluded, therefore, that meat and bone meal exposure, through feed, occurred prior to implementation of the Canadian feed ban.

Depopulation Of Canadian Cattle

The CFIA identified animals in Canada for depopulation and testing, consistent with current BSE guidelines published by the Office International des Epizooties (OIE) and the recommendations of the International panel which reviewed the May 2003 case.

The index case was born on April 9, 1997. The animals subject to culling under OIE guidelines were those animals born one year before and after the index case, known as the birth cohort. Therefore, the trace out investigation centred on animals born between April 1996 and April 1998.

Fifty-seven (57) animals were born into the birth herd from April 1996 to April 1998. Twenty-seven (27) of these animals were traced and confirmed dead, 25 animals (including the index case) were exported to the US, two animals were untraceable, and three animals were continuing to reside in Alberta. A quarantine notice was served on the three animals in Alberta on January 23, 2004. The three animals were evaluated for compensation, humanely transported to the CFIA laboratory in Lethbridge, Alberta for euthanasia, and tested negative for BSE.

A related premises also had 57 animals born during April 1996 to April 1998. These animals might have been exposed to small amounts of potentially contaminated feed through common management practices, including sharing of feed. Of these 57 animals, 48 were dispersed and 9, still on the farm, were quarantined on January 28, 2004. The nine animals were evaluated for compensation, humanely transported to the CFIA laboratory in Lethbridge, Alberta for euthanasia, and tested negative for BSE.

The 48 animals were determined to be among 86 head sold to numerous buyers. Eighty (80) of these were traced and confirmed slaughtered, 2 were untraceable and 4 were traced into a herd of 150 head. The 4 animals comingled with the herd of 150 may or may not be part of the birth cohort, and their risk of exposure is low. All animals within the herd of 150 are being identified to ensure future traceability.

In total, 12 animals were destroyed and tested in Canada and test results for all 12 animals were negative for BSE. The disposal of these animals was in accordance with international guidelines and with provincial and local authorities.

In the May 2003 BSE case, approximately 2,700 animals from the investigations in Alberta and Saskatchewan were destroyed. This action reflected the challenges regarding the identification of the infected animal, the difficulty in determining its herd of origin and the sizes of the multiple operations that were involved in the animal’s history.

Import Measures

Import measures continue to be applied with the cooperation of the Canada Border Services Agency. Based on current science, there is continued importation of products and animals which do not pose a risk to human or animal health. These include boneless beef from cattle aged 30 months or less at slaughter, live cattle destined for immediate slaughter, and dairy products, semen, embryos and protein-free tallow. Discussions have been initiated with the US on certification for boneless beef and other products covered by the exemptions. The appropriateness of interim restrictions are under active review based on the findings of the US investigation and subsequent adjustments to meat inspection policies and procedures in the United States.

Enhanced BSE Measures

Several measures have been or will be taken to enhance the effectiveness of BSE policies in Canada. These include enhancements of BSE surveillance measures (e.g. sampling and testing) which are being implemented. With the implementation of these measures, the number of animals tested annually for BSE has been increased to determine the disease prevalence in Canada. Testing will target those animals most at risk of expressing BSE, thereby providing the most effective and efficient means of determining prevalence and monitoring the effectiveness of CFIA’s disease control measures.

The Government of Canada is working with the Canadian Cattle Identification Agency to assess new identification technologies to further improve tracking and tracing capacity and strengthen compliance verification activities.

In addition, consultations with the provinces, trading partners and industry sectors are underway to determine the best feed regulations to enact to prevent exposure to BSE.

These measures are in addition to the restrictions requiring the removal of specified risk materials (SRMs) from all animals slaughtered for human food at abattoirs and beef processing facilities in Canada which went into effect last summer to protect Canadian beef consumers.

Conclusion

The CFIA successfully traced the history of the recent BSE-positive cow found in Washington state. The investigation of the other animals in the birth herd and a related premises has been completed. BSE exposure most likely occurred prior to implementation of the Canadian feed ban. The findings continue to indicate that the suite of measures adopted in Canada and the US over the past fifteen years have achieved the intended result of minimizing the effect of BSE in the cattle population and protecting public health.

The CFIA has also compared this case to the earlier BSE case in May 2003 to determine if they were linked by cattle movement or a common feed source. The CFIA’s investigation has not yielded any conclusive evidence that would link the two cases.

The information gathered over the course of the investigations would suggest that the appearance of BSE in North America was likely due to the importation of cattle from the United Kingdom (UK) from 1982 to 1989 when the disease was first emerging and the understanding of the disease was extremely limited. From this group of animals, it is possible that a low level of infectivity entered into the animal feed chain prior to the decision in Canada to remove all remaining imported animals in 1993.

A further detailed assessment of these imported animals, their herds of origin in the UK, their slaughter or death and resulting use of rendered materials and feed distribution in the period from 1986 to 1993 will be the focus of another phase of inquiry.

Current information indicates that the BSE case in the US does not pose a health risk to Canadians. The CFIA investigation has shown that no meat from this animal entered the Canadian food system. Canadian beef continues to be safe for consumption both domestically and as exports.

Source: Canadian Food Inspection Agency - September 2003

5m Editor