Last week, the Canadian Food Inspection Agency concluded their epidemiological investigation of a 50-month old dairy cow found to have BSE last month. CFIA investigators say the most likely route of transmission is from pelleted heifer feed purchased from a feed mill.

Because the animal was exposed to BSE after the 1997 implementation of Canada’s feed ban, the CFIA placed priority on conducting a comprehensive review of all potential routes of BSE exposure.

In general, investigators observed good levels of compliance with the feed ban at the farm, retail and manufacturing levels. The investigation revealed that despite having protocols in place to comply with the 1997 feed ban, a feed mill apparently failed to properly clean equipment after making pelleted feed for non-ruminant animals that contained prohibited material. A single batch of feed was probably contaminated. And the entire batch of feed was shipped to the BSE-positive animal’s farm. While the investigation looked at all possible routes of exposure, this particular batch of feed is the most probable source of infection.

The CFIA has launched an enforcement investigation of that feed mill.

The animal died of causes unrelated to BSE and would likely have lived for an additional four to six months before the onset of BSE-related clinical signs. This age range is not significantly different from that of previous Canadian cases and indicates exposure to only a very low dose of BSE infectivity. The detection of this case at the earliest possible moment demonstrates the highly sensitive nature of Canada’s national BSE surveillance program, which targets cattle from the highest risk populations and has tested more than 117,000 animals since 2003.

A complete summary of the investigation is available on the CFIA’s website.

Canadian Food Inspection Agency