TORONTO - No other cases of mad cow disease have been found in the Western Canada herd where a 6-year-old cow was found with the crippling brain ailment, authorities reported yesterday.
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 cattle industry, which faces the possibility of North America's first home-grown case of bovine spongiform encephalopathy, or BSE, which has been linked to a fatal nerve disease in humans through the consumption of contaminated meat.
The fact that no other cow in the original herd was infected is "encouraging news," Brian Evans, Canada's chief veterinarian, told reporters in Ottawa.
"The negative test results ... means that the incidence of BSE in Canada presently remains confined to one farm," 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 19 yesterday and zeroed in on an Alberta farm where the infected cow likely spent four years of its life before being sold to the 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 because cows are more susceptible to BSE at a younger age. Authorities are not yet certain where the cow originated, but are tracking two possible paths, one of them leading to a purebred Angus breeder in Saskatchewan, Mel McCrae, another to a farm in Alberta.
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 United States 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.
Kim Murphy writes for the Los Angeles Times, a Tribune Publishing newspaper.