More tests for mad cow come back negative

TORONTO -- Test results on three more cattle herds linked to a lone case of mad cow disease in Canada came back negative Friday, and a government inspector said the investigation into the infection could be over by the end of next week.

Brian Evans, chief veterinary officer of the Canadian Food Inspection Agency, said two herds that received calves from the infected cow's last herd tested negative for bovine spongiform encephalopathy, or BSE.

Another herd where the infected cow lived for up to four years also tested negative, he said.

Animals must be killed to be tested, and 370 animals, including the 192 in the infected cow's last herd, have been slaughtered for testing so far, with no further cases found. More than 600 animals must still be tested.

More than a dozen herds are under quarantine for the investigation. Officials are trying to find out where the infected cow came from and what feed it ate.

Several countries, including the United States, banned all Canadian beef products after officials announced on May 20 that one BSE case had been detected in Alberta, the heartland of Canada's cattle country. It was the first reported BSE case in North America in a decade, and only the second ever on the continent.

Canada and the United States have discussed relaxing the U.S ban, which closed the main market for Canadian beef, even while the investigation continues.

Evans said if all further tests come back negative, the investigation could be done by the end of the upcoming week. Authorities insist the infected animal did not enter the human food chain.

Three farms in British Columbia received poultry feed made from the cow's carcass. Poultry cannot contract BSE, but officials cannot prove that cattle at the farms never ate the feed.

Mad cow disease was first diagnosed in Britain in 1986 and is thought to have spread through cow feed made with protein and bone meal from mammals.

Canada banned the use of ruminant animal-based feed for cattle in 1997. The infected cow could have eaten infected food before the ban took effect because it was believed to be between 6 and 8 years old when it was killed.

The human form of BSE is the fatal brain-wasting illness variant Creutzfeldt-Jakob disease. Scientists believe people get it by eating some meat products from infected animals.