U.S. officials said they cannot find the birthplace of the latest U.S. case of mad cow disease but see little risk that the birth herd is harboring more cattle infected with bovine spongiform encephalopathy (BSE). “Experience worldwide has shown that it is highly unusual to find [mad cow disease] in more than one animal in a herd or in an affected animal's offspring,” U.S. Department of Agriculture (USDA) chief veterinarian John Clifford said, announcing the investigation was closed. In the two previous U.S. cases, the birth herd was located, a USDA spokesman said Wednesday. The first, a dairy cow in Washington state, was tracked to a Canadian farm. The second, a beef cow in Texas, spent its life on the same farm. The latest case, reported on March 13, was a beef cow in Alabama that was purchased less than a year before it became sick. It was difficult to track, Clifford said, because it was more than 10 years old and carried no tattoos, ear tags, or branding marks. The case complicated U.S. efforts to persuade Japan to reopen its markets to American beef.
