Cattle eat feed as a truck pours food into their trough on a feedlot near Airdrie, Alta. (Jeff McIntosh/Canadian Press)

A feed manufacturer in B.C. is the most likely source of Canada's 13th case of mad cow disease, according to a report by the Canada Food Inspection Agency.

The report released on Thursday says the case involves a five-year-old dairy cow from British Columbia's Fraser Valley, which tested positive for the disease in June.

Since then, an additional case of bovine spongiform encephalopathy (BSE) was discovered in Alberta in August.

The 13th case and all 12 previous BSE cases likely came "through incidents of accidental cross-contamination, which may occur in the complex feed and manufacturing system," the agency's Dr. Connie Argue said Thursday.

Because the incubation period is four to six years, officials believe the animal from the Fraser Valley was contaminated as a calf, the report says.

The food source was narrowed down to an unnamed food supplier of heifer ration that also manufactured food for other non-ruminant animals that contained material prohibited from cattle, sheep and goat feed.

Two other unnamed feed manufacturers where prohibited material was handled were also mentioned in the report as potential areas for cross-contamination.

The report says the feed did not contain banned protein on purpose, but may have been contaminated by equipment used to process non-ruminant feed.

"Bulk ingredient receiving and finished feed conveyances were cross-utilized," the report said.

The agency said a total of 207 other animals connected to the diseased cow either have been or will be destroyed.

"The detection of this case does not change any of Canada's BSE risk parameters," the report concluded. "The location and age of the animal are consistent with previous cases."

When asked if there was concern for other farms that used feed from the suspect manufacturers, Argue said the investigation is limited to feeds that were given to the animals on the same farm at the time.

Canada, which is classified under the world organization for animal health as a controlled BSE risk country, brought in changes more than a decade ago to stop animal products from being fed to cattle, sheep and goats and prevent the transfer of BSE into the food chain.

When the first Canadian case was discovered in 2003, the U.S., Japan, South Korea, Australia and several other countries imposed a temporary import ban on Canadian beef.

Last year, the Canadian government extended regulations to eliminate all risk materials, tissues that have been shown to harbour BSE infection, from all animal food, pet feed and fertilizer.

"The enhancements to the feed ban are meant to accelerate BSE eradication in Canada," Argue said.

She predicted there will be more animals diagnosed with BSE in the next few years but said the fact that infected animals continue to show up is a testament to how vigilant the inspection process is in Canada.