Aug 25, 2006 (CIDRAP News) A procedural error at a feed mill might have resulted in contamination of cattle feed with banned materials and caused Canada's seventh case of bovine spongiform encephalopathy (BSE), or mad cow disease, the Canadian government said yesterday.
The government also said the cow involved died of mastitis, not BSE. The animal was showing no outward signs of BSE at the time of death, but was tested because it met other criteria for BSE testing, the Canadian Food Inspection Agency (CFIA) reported.
The case, reported Jul 13, was in an Alberta dairy cow born in April 2002, years after Canada's 1997 ban on feeding of cattle parts to cattle and other ruminant animals. Because of this, the CFIA had said the cow's feed history would be the main focus of its investigation of the case.
Investigators found generally good compliance with the feed ban at all levels, the CFIA said. However, a review of records at one feed mill showed that equipment was used to process feed for nonruminant animals and then was used to process one batch of cattle feed without being cleaned in between. The feed for nonruminants contained materials banned from cattle feed.
The batch of potentially contaminated cattle feed, intended for heifers, was delivered to the farm where the cow in question was being raised and was used there, the CFIA said. The agency said an enforcement investigation is under way.
"The procedural error associated with the 16% Heifer Grower ration makes that feed the most likely source of infection," the agency said.
The report says that if the cow had not died of mastitis, it would have shown signs of BSE in another 3 to 6 months.
Investigators found 172 cattle that were born or raised on the same farm as the infected cow and might have had the same feed, the CFIA reported. Most of these were confirmed to have died or been slaughtered previously, but 38 were found still alive and were subsequently euthanized and the carcasses burned. Four other live animals have been quarantined temporarily to allow for calving or collection of valuable genetic material and will be destroyed later.
The CFIA said it has increased its inspection and enforcement efforts related to the feed ban in the past year, adding about 115 staff members in those areas. In 2005, Canadian and US Department of Agriculture officials reviewed and confirmed the effectiveness of Canada's feed ban, the agency said in a news release.
"Nonetheless, the extremely small infective dose of BSE means that even very limited opportunities for contamination may permit periodic cases," the agency said. "The emergence of such cases is common to almost every country reporting the disease."
Canada announced in June that it would ban potentially infective cattle parts (specified risk materials) from all animal feeds, not just ruminant feeds. That ban is to take effect in July 2007.