Canada on Sunday confirmed its second case of mad cow disease (search), just days after the United States 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 (search). 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 December 2003 to have the disease.

The U.S. Department of Agriculture (search) 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 U.S. livestock and consumers.

Food contaminated with BSE can afflict people with usually fatal variant Creutzfeldt-Jakob disease.

The 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. "I think it's pretty much where we were last week. We've been working closely with Canadian officials."

Harrison said U.S. 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 on Tuesday.

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 Bush on Friday about the new suspected case. Martin sought assurances that it would not mean a re-closure of the U.S. 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 United States. That market was worth $1.5 billion in 2002.

The decision to allow Canadian cows into the United States in light of the latest scare brought sharp responses from several Democratic lawmakers last week.

Rep. Earl Pomeroy, D-N.D., called the decision "outrageous" and accused the Agriculture Department leadership of caring "more about the interests of mega feed lots and processors than the interests of farmers, ranchers and consumers."

Ron DeHaven, administrator of the agriculture department's Animal and Plant Health Inspection Service, has said beef brought into the United State will be subject to Canadian inspection and subject to re-inspection by the USDA Food Safety and Inspection Service.

The USDA ruling, effective March 7, declared Canada a "minimal-risk region" so that cattle could be shipped into the United States under certain restrictions. The cattle must be slaughtered by the age of 30 months, which scientists say is too young to contract mad cow disease, and they must be transported in sealed containers to a feedlot or slaughter house.

The discovery in Washington state a year ago is the only confirmed case of mad cow disease in the United States. There have been a handful of suspected mad cow cases during preliminary screening in the United States, but more sophisticated tests produced negative results for the disease.

Both the beef industry and the USDA acknowledge that eventually another mad cow case is likely to be discovered among the 40 million adult cattle in the United States. About 1 percent of the herd, or 446,000 cattle, are considered in the targeted "high risk" category, according to the USDA, because they are not ambulatory and do not show signs of other ailments.

Darcy Davis, chair of Alberta Beef Producers, said Sunday the new case should not cause too much concern among Canadian beef producers.

"It's an ongoing concern with BSE, but at the same time we have the safeguards in place and we're handling it scientifically now and we know that we have an extremely low incidence," Davis said.

While investigators have identified the latest infected animal's farm of origin, they were shifting their efforts Sunday to identify any other animals of similar risk — specifically, recently born offspring of the infected animal and cattle born on the same farm within a year of the infected animal.