Authorities confirmed on Tuesday another case of mad cow disease in the western province of Alberta -- the second animal found to have the deadly brain-wasting disease in Canada since US officials announced last month they would resume the cross-border cattle trade in March.
Canadian officials said no part of the cow -- the third case of the disease ever found in Canada -- had entered the human or animal feed system.
But the announcement may strengthen the position of a group of US cattlemen who have sued to block the lifting of the ban. The cattlemen say allowing the trade will hurt US producers and put consumers at risk.
US Department of Agriculture officials said on Tuesday they are sending a team to Canada to evaluate the latest mad cow case before deciding whether to change their plan to resume imports.
Ron DeHaven, administrator of the Agriculture Department's Animal and Plant Health Inspection Service, said the agency is confident that protections in place in Canada and the US will safeguard US consumers and livestock.
The latest case of bovine spongiform encephalopathy (BSE) was discovered in an animal under seven years old. Canadian Minister of Agriculture Andy Mitchell said the case was unrelated to the second case of the disease, which was confirmed Jan. 2 and also involved an Alberta cow.
"A third case of BSE in a cow in Canada has been confirmed today through our surveillance system," Mitchell said in a news conference in Ottawa, the nation's capital. "This is not unexpected, as we have already acknowledged that there is a low level of incidence of BSE in North America."
The latest sick cow was born after a 1997 feed ban in Canada removed the use of animal remains in feed, commonly believed to be the cause of the disease. This makes the case of this third Canadian cow with BSE more serious than the others because the cause could be much more difficult to trace.
However, Dr Brian Evans of the Canadian Food Inspection Agency said the cow was most likely exposed to feed before the ban came into effect in the fall of 1997 and that his agency was investigating.
Nevertheless, Mitchell stressed the new case was not a cause for alarm.
"The rules upon which beef should move between countries should be based on science, and we believe that Canada has clearly followed a scientific approach," he said.
Mitchell pledged that Canada would toughen measures to stem the disease and that the Canadian Food Inspection Agency, with an independent third party, would conduct an audit of the country's animal feed safety.
The Jan. 2 case was announced after the disease was detected in an 8-year-old cow from Alberta. It was born in the same herd -- within one year -- of a cow shipped to the US in February 2002 for immediate slaughter, the USDA said.
Canada's first case of mad cow surfaced in May 2003, prompting the US government to close the border to Canadian beef imports. Concerns persisted after a Canadian-born cow in Washington state was found in December 2003 to have the disease, which attacks the animal's nervous system.
All three cases have involved animals from Alberta.
On Dec. 29, the Bush administration announced plans for lifting the ban.
After learning of the second case days later, the administration had said it would stand by its decision, expressing confidence that public health measures in both countries will protect US livestock and consumers.