Investigators tentatively traced the first US case of "mad cow disease" to Canada, which could help determine the scope of the outbreak and might even limit the economic damage to the country's beef industry.
In addition, some calves in a quarantined herd of 400 that included a male offspring of the sick cow will probably be destroyed, the US Agriculture Department said yesterday. The herd was at a farm in Sunnyside, Washington.
Dr Ron DeHaven, the Agriculture Department's chief veterinarian, said that Canadian officials provided records indicating the sick Holstein dairy cow was in a herd of 74 cattle shipped from Alberta, Canada, in August 2001.
"These animals were all dairy cattle and entered the US only about two or two-and-a-half years ago, so most of them are still likely alive," Mr DeHaven said.
The sick cow's presence in that herd does not mean all 74 animals are infected, he said. Investigators will probably find where the other 73 animals are within a matter of days. 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 beef industry because the US could keep its disease-free status and continue trade.
The National Cattlemen's Beef Association in Denver said the indication that the infected cow was from Canada means US trading partners should reopen their borders to US beef. The farm organisation said a beef export monitoring programme would allow importers to separate beef of Canadian origin if they feel additional precautions are needed.
Federal officials announced earlier this week that tests indicated the cow, which ended up at a Washington farm in October 2001, had bovine spongiform encephalopathy (BSE). An international laboratory in Britain confirmed it on Christmas Day.
Scientists believe that human consumption of BSE infected beef products can lead to the development of variant Creutzfeldt-Jakob disease. In Britain, 143 people died of it following an outbreak of BSE in the 1980s.
More than two dozen countries banned US beef this week. The US lost 90 per cent of its beef export market, industry officials said.
AP