TORONTO - Seven herds of cattle are now under quarantine in Canada, investigators said Thursday as officials broadened their search for the origins of North America's first case of mad cow disease in a decade.
Records indicate the infected cow may have been born in Saskatchewan province, Claude Lavigne of the Canadian Food Inspection Agency told a news conference Thursday.
If so, it would be the first case of a North American-born animal contracting bovine spongiform encephalopathy, or BSE, which decimated the British beef industry in the 1990s. The only previous case of mad cow disease in North America, in 1993, involved a bull imported from Britain.
The United States banned beef imports from Canada following Tuesday's announcement that a cow from a herd in northern Alberta had contracted the disease. The U.S. market is Canada's largest, accounting for more than 80 percent of Canadian beef exports.
Four more cattle herds were placed under quarantine on Thursday, Lavigne said, including three with calves that had come from the herd where the infected cow last lived. Three other herds were already under isolation, and two more were likely to be added to the list.
Canadian investigators have removed all the cattle from the Alberta farm the infected cow last lived in and were destroying the herd to examine the brains for possible cases of BSE. Test results were expected early next week; the findings will determine if the other quarantined herds get destroyed.
Five of the herds under quarantine are in Alberta, the heart of Canada's cattle country, and two in neighboring Saskatchewan, Lavigne said.
Despite the expanded quarantine list, "there's no evidence at this time that the safety of Canada's beef has been compromised in any way," he said. "Information strongly suggests that the risk to human health from this one cow is low."
Still, the closing of major foreign markets to Canadian beef brought immediate cuts in production and uncertainty to a major industry. Japan, Australia, South Korea and New Zealand have also banned Canadian beef imports.
Elden McLachlan, who runs a 300-head herd near the northern Alberta farm where the stricken cow last lived, called the situation "a very big shock."
The infected cow's owner, identified by neighbors and his brother as Marwyn Peaster, shooed away reporters and refused comment. Peaster, 30, moved from Mississippi to Alberta in recent years, said his brother Camron.
Lavigne said officials still don't know how the stricken cow contracted BSE, and noted that a records search had even raised questions about the infected cow's age. Originally thought to be 8 years old, it may actually be 6, he said.
Fearing harm to Canada's $22 billion beef industry, government and industry officials sought to assure the world that Canadian beef was safe.
Prime Minister Jean Chretien said he and visiting French Prime Minister Jean-Pierre Raffarin would eat steak on Thursday.
"I shall eat Canadian meat without any problem," Raffarin told a news conference, drawing a laugh.
A report by J.P. Morgan Canada said Canada's economic growth could be reduced by half a percentage point or more if the beef import bans last until the end of June.
The infected cow was slaughtered Jan. 31 but kept out of the food chain because it was believed to have pneumonia, officials said.
The head was sent to a provincial laboratory for routine testing. Because there was no suspicion of BSE then and the animal was not used for food, the sample had a low priority and was put in a backlog numbering hundreds for more than three months, said Dr. Gerald Ollis, Alberta's chief veterinarian.
When testing indicated the possibility of mad cow disease, the samples were sent to a British laboratory that confirmed it Tuesday.
Mad cow disease first erupted in Britain in 1986, and is thought to have spread through feed made of protein and bone meal from mammals. Canada and the United States outlawed meat and bone meal feed for cattle, sheep and goats in 1997, believed to be the main defense against the disease.
The human form of mad cow disease, Creutzfeldt-Jakob disease, causes paralysis and death. Scientists believe humans develop variants of Creutzfeldt-Jakob when they eat meat from infected animals.