Canada confirmed its second case of mad cow disease, just days after the US said it planned to reopen its border to Canadian beef.
The dairy cow from Alberta, which was born in 1996, has tested positive for bovine spongiform encephalopathy, as mad cow disease is formally known, according to the Canadian Food Inspection Agency on Sunday.
The results confirmed preliminary tests released earlier this week.
The border was closed 19 months ago when a cow in northern Alberta was discovered with mad cow disease, which attacks the animals' nervous system. Concerns persisted after a Canadian-born cow in Washington state was found in Dec. 2003 to have the disease.
The US Department of Agriculture announced Wednesday that the border could be opened in March.
Despite learning of the new suspected case, the Bush administration said the next day that it would stand by its decision to renew Canadian cattle imports, expressing confidence that public health measures in both countries will protect US livestock and consumers.
Food contaminated with BSE can afflict people with the usually fatal variant Creutzfeldt-Jakob disease.
The US Agriculture Department suggested Sunday that its stance would not change.
"I don't anticipate that this confirmation will change implementation of our rule," department spokeswoman Alisa Harrison said Sunday.
Harrison said US officials had considered the possibility of additional confirmed mad cow cases in Canada and their action was "based on guidelines set by the World Health Organization." She said the rule is to be formalized today.
Under the WHO guidelines, Harrison said, a country with a cattle population of 5.5 million head over 24 months of age like Canada could have 11 cases of mad cow during a consecutive 12-month period and still be considered a minimal risk country.
The Canadian Food Inspection Agency said the infected cow did not enter the human food or animal feed supply and posed no risk to the public.
Canadian Prime Minister Paul Martin spoke to President George W. Bush on Friday about the new suspected case. Martin sought assurances that it would not mean a re-closure of the US border to Canadian beef imports, and Bush assured him that his administration is committed to keeping the border open, a Canadian official said on condition of anonymity.
Authorities said the cow was born in Alberta in 1996, prior to the introduction of the 1997 feed ban. It is suspected that the animal became infected by contaminated feed before the ban.
BSE is a chronic, degenerative disorder affecting the central nervous system of cattle. Since it was first diagnosed in Britain in 1986, there have been more than 180,000 cases.
Before the trade ban, animals regularly crossed the border and Canada sold more than 70 percent of its live cattle to the US. That market was worth $1.5 billion in 2002.
The decision to allow Canadian cows into the US in light of the latest scare brought sharp responses from several Democratic lawmakers last week.