As of
May 2007, fourteen cases of BSE have been identified in North America. Of these fourteen cases,
three were identified in the U.S. and eleven in Canada. Of the three cases identified in the U.S., one was born in Canada; of the 11 cases identified in Canada, one was imported from the United Kingdom. The proportion of Canadian-born BSE cases identified by Canadian authorities through the testing of animals in Canada, 2003-April 2007 (10 cases among approximately 160,000 animals tested) is presently statistically significantly higher (26 fold higher) than the proportion of U.S.-born BSE cases identified by U.S. authorities through the testing of animals in the U.S. during the comparable period (2 cases among more than 875,000 animals tested).
Six of the eleven BSE cases in Canadian-born cattle were known to have been born after the implementation of the 1997 Canadian feed ban; five of these six were born more than eighteen months afterwards. One of the eleven Canadian-born BSE cases was reported in an animal that was born either before or shortly after implementation of the 1997 feed ban.
The BSE strain that is responsible for most of the BSE cases in Canada is the same strain linked to the outbreak in the United Kingdom. This strain has not yet been identified in any U.S.-born bovine.
Both of the U.S.-born BSE cases and one Canadian-born BSE case were 10 years of age or older and all three of these older cases were linked to an atypical BSE strain known as the H-strain.
One (9%) of the 11 Canadian-born BSE cases and 2 (100%) of the U.S.-born BSE cases occurred in animals that were known to be at least ten years of age. These significantly different (P<.05) proportions correlate with the observed BSE strain differences in the two countries because, to date, only the older cattle have the atypical H strain.
The Canadian Food Inspection Agency (CFIA) is enhancing Canadian feed controls to more effectively prevent and quickly eliminate BSE from Canada. CFIA’s new feed control regulations will ban most proteins, including potentially BSE infectious tissues known as “specified risk materials” (SRM) from all animal feeds, pet foods, and fertilizers, not just from cattle feed as required by the ban instituted in 1997. The 1997 feed ban in Canada was similar to the feed ban instituted in the United States that same year. As recently reported by CFIA, removing SRM from the entire animal feed system addresses risks associated with the potential contamination of cattle feed during production, distribution, storage, and use. Applying the same measure to pet food and fertilizer materials addresses the possible exposure of cattle and other susceptible animals to these products. This enhanced Canadian feed ban is scheduled to come into effect on July 12, 2007. CFIA expects that with this new ban, BSE should be eliminated from the Canadian cattle herd by about the year 2017.