CALGARY - Federal Agriculture Minister Gerry Ritz says figuring out how an Alberta cow was infected with BSE is like looking for a needle in a haystack.
The beef breeding cow was discovered last month on a farm near Edmonton and was born on a nearby farm. Another cow born at the same location in 2004 tested positive for bovine spongiform encephalopathy in 2010.
Officials have said that no material from either cow made it into human or animal food.
BSE is a fatal and untreatable wasting disease of the brain and nervous systems. It is caused by rogue proteins called prions, which can be spread through contaminated feed.
The Canadian Food Inspection Agency continues the complex task of checking cattle born on the farm to see whether they may have been exposed to the same feed as the BSE cow, although it hasn't been determined yet whether infected feed caused the disease in this case.
"It takes such a miniscule amount of product that it's a needle in a haystack ... it's a needle in several haystacks actually," Ritz said at a news conference in Calgary.
"It's quite a large operation, the birth farm, as well as the farm she was found on, so there's a number of animals to be searched out," he said.
"I think they've identified some 40 to 50 per cent already and continue to move forward on that. At the same time, they do the feed trace to find out if there's any type of smoking gun throughout the feed system as well."
Humans who eat infected beef can develop a fatal disease called variant Creutzfeldt-Jakob disease. Fewer than 250 human cases have been reported worldwide.
Ritz says a number of countries that have temporarily suspended imports of Canadian beef are being kept in the loop, but he points out they only account for about five per cent of Canada's worldwide market.
"Our chief veterinary officer has been staying in close contact with the rest of the markets making sure they're apprised almost on a day-to-day basis as to how the investigation is proceeding," Ritz said.
"So far everyone is holding tough. The world recognizes us as a controlled-risk status country. That's science-based and we expect our trading partners to base their access decisions on that science."
Ritz was in Calgary for the official opening of the Canadian Beef Centre of Excellence. Ottawa invested $3.4 million to help set up the centre, which is being operated by Canada Beef Inc., a national organization that handles research, marketing and promotion of the Canadian cattle and beef industry worldwide.
The facility will provide space and resources to help the industry promote new beef products, training and education focused on the technical advantages of Canadian beef.
It will also provide training to companies interested in trade missions and help the industry test-market new products and gather feedback from consumers.
Follow @BillGraveland on Twitter.