A SECOND cow in the US has tested positive for BSE, just in time for Fourth of July barbecues. A programme to test more than 200,000 cattle, launched in June, has so far examined 7000 animals. Finding a positive so quickly could just be bad luck, or it could indicate a significant prevalence of BSE in the US herds.
The Department of Agriculture (USDA) says the test result is 鈥渋nconclusive鈥� until it has been confirmed by a slower, more reliable test, and that it is 鈥渉ighly likely鈥� the animal did not have BSE. But the California firm BioRad, which made the test, says its ultimate false positive rate after confirmatory tests is only 1 in 300,000. That means the test result is only likely to be wrong if the US鈥檚 rate of BSE infection is substantially lower than the test鈥檚 false positive rate.