WASHINGTON, Nov. 23 (UPI) -- U.S. officials said Tuesday confirmatory tests on a cow that had initially tested positive for mad cow disease found no evidence of the deadly disease.
The cow had tested positive last week on two rounds of so-called rapid tests. The U.S. Department of Agriculture ran a more sophisticated test, called an immunohistochemistry or IHC test and it came back negative Monday, John Clifford, deputy administrator of the agency's Animal and Plant Health Inspection Service, said in a statement.
Because of the two positive rapid tests, USDA officials ran the IHC test a second time. Again, it returned a negative result Tuesday.
"Negative results from both IHC tests makes us confident that the animal in question is indeed negative for (mad cow disease)," Clifford said.
Humans can contract a fatal illness called variant Creutzfeldt Jakob disease from eating beef products contaminated with mad cow.
The USDA has tested more than 121,000 cows since December when a case of mad cow was detected in Washington. Three cows have initially tested positive on the rapid tests, but all turned out to be negative on IHC tests.
