Tests of First Herd Prove Negative for ‘Mad Cow’

No other cases of “mad cow” disease have been found in the western Canadian herd that was home to a 6-year-old cow diagnosed with the crippling brain ailment, authorities reported Sunday.

But Canadian health officials did not rule out the possibility of wide-scale cattle slaughters to guarantee the integrity of Canada’s $21.9-billion livestock industry, which faces the probability of North America’s first home-grown case of bovine spongiform encephalopathy. BSE has been linked to a fatal brain-wasting disease in humans through the consumption of contaminated meat.

The fact that no other cow in the original Alberta herd was infected is “encouraging news,” Brian Evans, chief veterinary officer for the Canadian Food Inspection Agency, told reporters in Ottawa.

“The negative test results ... means that the incidence of BSE in Canada presently remains confined to one farm,” he said. “It also sends a clear message to the world that our systems are continuing to respond to the situation,” he said.

The findings so far “strongly indicate that the risk to human health also is extremely low,” Evans added.

Investigators widened the number of farms under quarantine to 17 Sunday. Herds are under quarantine in three provinces, Alberta, Saskatchewan and British Columbia, but officials are zeroing in on another Alberta farm where the infected cow probably spent four years of her life before being sold to the Wanham farmer whose herd was tested this week.

Those results will be crucial, both because the cow spent a much longer period at that farm, and also because cows are more susceptible to BSE at a younger age. Authorities are not yet certain where the cow was born but are tracking two possible paths, one of them leading to an Angus breeder in Saskatchewan, Mel McCrae, another to an undisclosed farm in Alberta.

McCrae said he expected DNA tests this week would provide conclusive evidence whether or not the cow originated on his farm.

The problem, investigators said, is that the cow’s birth predates the unique tracking system now in place in Canada that provides a complete history of a cow’s movement from farm to feedlot to slaughterhouse by way of an electronic ear tag. That system was started in 2001 and fully implemented only last year.

“This cow didn’t have good ID,” explained Cheryl James, a veterinary epidemiologist for the Canadian Food Inspection Agency. “It could be a black cow from here, or a black cow from there. We’re tracing through people’s records, through people’s memories, through any means we can. Then once we work it down, there’s a potential that we may be able to use some DNA testing to actually confirm where it came from.”

Authorities are also tracking progeny of the infected cow, since BSE in rare instances can be passed on from mother to calf. But Evans said one of the most promising leads involves the Alberta herd in which the cow spent four years of her life. All 75 animals in that herd have now been tracked to three different farms, and investigators over the weekend are in the process of seizing those cows for euthanasia and testing.

“That’s of great significance to us,” Evans said. Equally important, he said, will be tracking down “birthing cohorts” -- calves born at the same time on the same farm as the infected cow. They would be expected to have the greatest chance of also developing mad cow disease if they were exposed to, say, contaminated feed.

Canadian health officials have emphasized that the widening number of farms under quarantine is no indication that the risk of infected cows is greater. Rather, they said, it merely indicates that the detective trail on the same cow has led them in different directions.

“The investigation is advancing, not the disease,” Evans said.

But there have been growing signs that Canadian officials may be prepared to order wholesale slaughters of a large number of herds connected to the inquiry, if only as a means of restoring public confidence.

The U.S. and several other nations have banned imports of Canadian beef pending the outcome of the inquiry, a move which by some estimates is costing the industry $6 million to $11 million a day.

While slaughtering all of the possibly 1,000 cattle now under quarantine would be unfair, Alberta Agriculture Minister Shirley McClellan said, “I would expect, whether there’s a scientific reason for doing so or not, that the public confidence will demand something in that order.”

Provincial leaders also appear to be moving toward that view. “The ministers support erring on the side of caution,” Louise Greenberg, assistant deputy minister of Saskatchewan agriculture, told reporters. “We will take action, whatever it takes to restore public confidence ... in the safety of our beef industry.”

Of the 17 farms under quarantine, 12 in Alberta and two in Saskatchewan relate directly to the infected cow or her progeny. Three others, in British Columbia, received chicken feed manufactured in part from the remains of the infected cow before the disease was diagnosed.

“We’re reasonably confident that we’re on top of this one, and we have contained any other animals that might have been a problem from moving into the feed chain,” Evans said.