EDMONTON, Alberta (AP) - Canada has confirmed its ninth case of mad cow disease since 2003, in an Alberta bull that died on a farm last week. The Canadian Food Inspection Agency said Wednesday that a mature bull tested positive for mad cow, or bovine spongiform encephalopathy.

Dr. George Luterbach, the agency's senior veterinarian for Western Canada, said the animal's death caused it to be identified as an "animal of interest" at the farm level as part of a national surveillance program.

Eating meat products contaminated with BSE has been linked to more than 150 human deaths, mostly in Britain, from variant Creutzfeldt-Jakob Disease, a rare and fatal nerve disease. No human deaths as a result of the disease have been reported in Canada.

Luterbach wouldn't identify where in the province the animal was when it died.

An investigation is under way to find other animals born within a year of the bull that may have been exposed to the same feed source, Luterbach said.

"These animals are removed, destroyed, tested and disposed of in a manner that they do not enter into the feed system," he said, adding officials are certain this particular bull also did not enter that system.

Eight previous cases of BSE have been detected in Canadian cattle since May 2003, when the discovery of an Alberta cow with the disease caused the United States to slam the border shut to cattle exports entirely.

The border reopened for Canadian beef from younger cattle within months of the original ban. But live cattle have only been allowed to move across the border since July 2005.

Five new cases were discovered in Canada in 2006, including one in a cow born five years after safeguards were adopted to prevent the spread of the disease.

"The small number of cases are, I suppose, unwelcome but on the other hand, not entirely unexpected," Luterbach said, adding other countries have seen a small number of "residual" cases after adopting strict feed regulations.

A ban on using cattle remains in feed in Canada went into effect in 1997 to guard against the spread of BSE.

A new, enhanced feed ban, which comes into effect on July 12, 2007, should see BSE eliminated from the national cattle herd within 10 years, the agency has said.

New rules proposed by the U.S. Department of Agriculture that would allow exports of older live Canadian cattle to resume are up for public review until March 12.

Almost one-third of the Canadian beef herd and one-quarter of the total herd is estimated to have been born before 1998.

Luterbach said he doesn't expect the latest case to have a negative impact on these plans.

"What's most important is that there's safeguards, there's a stringent suite of measures in place to prevent and eradicate BSE," he said. "We are open and transparent with the United States."