WASHINGTON — U.S. Department of Agriculture officials announced Thursday that they had discovered a possible new case of mad cow disease, but cautioned that the preliminary positive test was inconclusive.
Final results should be available from the USDA lab in four to seven days, officials said.
After the first U.S. case was discovered last December in a cow in Washington state, the USDA instituted a rapid-screening test on cows considered at risk for the disease -- older cattle, "downers" too ill to walk, cattle displaying symptoms of neurological ailments -- as well as on 20,000 healthy cows.
So far, 113,000 animals have been tested, and none have been found to be carrying bovine spongiform encephalopathy, or BSE, the disease that if passed to humans through eating contaminated meat can cause a brain-wasting ailment called variant Creutzfeldt-Jakob disease.
The USDA provided no information on the suspect cow's origin but did indicate it was in one of the high-risk groups.
Preliminary tests of two cows in the last 11 months have been positive, but subsequent tests proved they did not have the disease.
Officials said the suspect carcass did not enter the food chain or the animal feed supply.
"USDA remains confident in the safety of the U.S. beef supply," said Andrea Morgan, a deputy in the department's Animal and Plant Health Inspection Service.
Still, news of a preliminary positive test rattled the markets. Prices for live cattle futures for December delivery were down on the Chicago Mercantile Exchange, at times falling below the 3-cent-per-pound allowable trading limit.
Traders were worried less about domestic consumption -- Americans are still eating an average of about 200 pounds of beef per person a year, according to the American Meat Institute -- than about the promise of renewing beef exports.
Japan and other countries cut off all imports of American beef after the Washington state case was disclosed. U.S. beef exports to Japan alone in 2003 totaled about $1.4 billion, an industry group said.
Industry analysts said exports to Japan were scheduled to resume in July if certain conditions were met. Among these is better identification of animals so that importers can purchase only those certified as under 30 months of age and thus most likely to be free of the disease.
"Under our framework agreement with the Japanese, even if we have another case, it would not set us back," said Chandler Keys, vice president for government relations at the National Cattlemen's Beef Assn., a industry trade group in Denver.
First diagnosed in Britain in 1986, BSE affected 178,000 British cattle and resulted in the eventual destruction of 3.7 million animals. A virtual worldwide ban on British beef cost farmers there billions of dollars.
After the infected cow in the United States was identified last year, Agriculture Secretary Ann M. Veneman said that the nation's beef supply was safe, but that the USDA was issuing a beef recall "out of an abundance of caution." In addition, several hundred cattle linked to the same herd as the infected cow were slaughtered.
After Veneman announced Monday that she was resigning as Agriculture secretary, President Bush praised her leadership in "ensuring that we responded quickly and effectively to protect the American food supply following the discovery of BSE."
News of the preliminary positive test brought cautions from a wide array of groups, including the American Meat Institute and the Consumer Federation of America, urging consumers not to be alarmed. "Inconclusive test results are just what they sound like -- inconclusive," said J. Patrick Boyle, president of the institute, a trade association in Washington.
But the Center for Science in the Public Interest, a nutrition and food-safety advocacy group in Washington, criticized the department for not yet requiring identification of the country's 32 million head of cattle.
"Last December the Department of Agriculture promised they would implement a nationwide animal identification program," said Caroline Smith DeWaal, the center's director of food safety. "Today there is no system in place to trace an infected cow back to its farm of origin."