The Canadian Food Inspection Agency confirmed on Wednesday a new case of mad cow disease in Alberta.

It is Canada's fifth case in 2006 and the eighth since 2003, when the disease was first found in this country, officials said.

This year's total has included two other cows from Alberta and one each from British Columbia and Manitoba.

Fear of infection has disrupted Canada's beef and cattle exports for long periods, even though the number of cases is dwarfed by those in Britain and some of the two dozen other countries where the disease has been found.

CFIA said the latest dead cow is believed to have been old enough to have contracted the disease — known formally as bovine spongiform encephalopathy, or BSE — before Canada banned the use of cattle parts in cattle feed.

The disease is thought to be spread mainly in contaminated feed. It attacks victims through hard-to-destroy protein forms called prions, which can multiply in the brain, reducing it to a spongy wreck.

The risk of transmission to humans who consume meat from infected animals remains unclear.

No part of the latest cow's carcass entered the human food or animal feed systems, CFIA said.

Tracking down cow's birth farm

Information from the dead cow's owner and a private veterinarian suggests the animal was between eight and 10 years old, the CFIA said in a statement.

"Based on this range, exposure to the BSE agent likely occurred either before the feed ban's introduction or during its early implementation," it said.

A CFIA investigation is in progress to locate the cow's birth farm, verify the animal's age, and identify other cows from the herd and possible sources of contaminated feed.

"As has been done previously, the CFIA will conduct a complete epidemiological review of this case, the results of which will be made public," the agency said.

Brad Wildeman, vice-president of the Canadian Cattlemen's Association, says he's not too concerned about the discovery.

Wildeman says Canada is doing so much testing of its animals that it's not surprising more infected animals are being discovered.
  
"We probably have the most aggressive, safest beef supply of any country in the world."

"We just need to keep hammering that home to our international trading partners that when it comes to a safe, quality product, that we've got that to offer them."