A second cow has tested positive for Mad Cow Disease in the U.S.?and only a fraction of cattle are tested, so who knows how many infected cows there really are? However, the USDA says it's "very likely" that with further testing, the cow will turn out not to have Mad Cow Disease, even though the test they used is wrong only about once in a thousand cases.
Debora MacKenzie writes in New Scientist that the USDA is calling the positive results "inconclusive" until they do a second test, called an IHC, which is more reliable but slower. John Clifford, of the USDA's Veterinary Services Program, thinks "it's very likely this animal could be negative." The first test, call a BioRad test, is "designed to be extremely sensitive" in order to catch any possibly infected animal, some of which "will end up negative during further testing."
But Europe, which has long used the BioRad test, has found that it gives a false positive only about once in every thousand tests.
Mad Cow is nothing?compared to what happened in Lab 257.
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