USDA retesting animal for mad cow
WASHINGTON (CNN) -- Further testing is being conducted on the carcass of an animal that showed inconclusive results for mad cow disease in initial tests, the U.S. Department of Agriculture said Friday.
Additional tissue samples were being sent to the National Veterinary Services Lab in Iowa , according to Dr. John Clifford, a deputy administrator at the USDA.
A more conclusive result would be available sometime in the next four to seven days, he said.
The animal had not entered the food supply before the testing took place, he said, and the carcass was being held pending further results.
Rogue proteins called prions that cause bovine spongiform encephalopathy (BSE) -- the formal name for mad cow disease -- collect in the brain, central nervous tissue and small intestines of cattle.
Clifford refused to say where the animal was or even if it was a cow, steer or bull.
He also cautioned that false positives in such testing are not out of the question.
"This is not at all unexpected. Screening tests are designed to be extremely sensitive," he explained.
The government has recently begun using rapid test kits as part of a program to inspect more cattle, after a cow shipped into the country from Canada was discovered to have BSE.
Mad cow disease first appeared in Britain in the mid-1980s, and millions of cattle were slaughtered as a result.
BSE can make it impossible for cows to stand.
The disease is linked to a similar form of the incurable and fatal brain-wasting disease in humans, called variant Creutzfeldt-Jakob Disease, or vCJD.
According to the Centers for Disease Control and Prevention, 153 cases of vCJD have been reported worldwide: 143 in Britain, six in France and one each in Canada, Ireland, Italy and the United States. The Canadian, Irish and U.S. cases were reported in people who had lived in Britain.
Charlene Singh, the only U.S. resident thought to have vCJD, died June 20. (Full story)
CNN's Michael McManus contributed to this report.