Canada immediately took issue with the US assertion that a cow with mad cow disease discovered in Washington state had probably come from Canada, saying such a conclusion was premature.
"As yet, there is no definitive evidence that confirms that the BSE-infected cow originated in Canada," the chief Canadian veterinarian, Dr Brian Evans, said at a news conference.
The sick cow's presence in that herd does not mean all 74 animals are infected, DeHaven said. Investigators will probably find where the other 73 animals are within a matter of days, he said. Finding them will help investigators determine if any other animals are sick and need to be tested.
In May, Canada found a lone cow with the disease in Alberta but has not been able to determine the source of infection.
If US and Canadian officials confirm that the sick cow in Washington state came from Canada, it might save the export market for the American beef industry because the United States could keep its disease-free status and continue trade.
Federal officials announced on Tuesday that tests indicated the cow, which ended up at a Washington farm in October 2001, had the brain-wasting illness. An international laboratory in England confirmed it Thursday.
Mad cow disease, known as bovine spongiform encephalopathy, is a concern because humans who eat brain or spinal matter from an infected cow can develop variant Creutzfeldt-Jakob disease. In Britain, 143 people died of it after an outbreak of mad cow in the 1980s.
Federal officials insist the nation's meat is safe because the brain, spinal cord, and lower intestine -- parts that carry infection -- were removed from the cow before its meat was processed for human consumption.
Despite those assurances, more than two dozen countries banned imports of US beef this week. The United States lost 90 percent of its beef export market, industry officials say, and producers stand to lose up to $6 billion a year in exports and falling domestic prices. Agriculture Department officials went yesterday to Japan, a top buyer that has banned American beef, to discuss maintaining trade.
