Positive mad-cow test kept quiet for months

Although the Agriculture Department confirmed on Friday that a cow that died last year was infected with mad cow disease, a test the agency conducted seven months ago indicated that the animal had the disease. The result was never publicly disclosed.

Meanwhile, Canada, which two years ago was prohibited from exporting its cattle to the United States after a mad cow scare, has no intention of closing its borders to U.S. beef after the latest report, Canada's agriculture minister said Saturday.

The comments from Canadian Agriculture Minister Andy Mitchell came as Taiwan reimposed the ban on U.S. beef that it lifted just two months ago. Also, a Japanese government food safety panel expressed concern Saturday about the second confirmed American case, raising speculation that Tokyo may delay a planned resumption of U.S. beef imports.

The U.S. ban on Canadian cattle has cost Canada's ranching industry $5.6 billion and strained ties between the two countries. Canadian officials have regularly called for an end to the ban, and they said the U.S. announcement of its first homegrown case of mad cow confirmed their belief that keeping the border closed to Canadian cattle no longer served its stated purpose.

The delay in confirming the United States' second case of mad cow disease seems to underscore what critics of the agency have said for a long time: that there are serious and systemic problems in the way the Agriculture Department tests animals for mad cow disease.

Indeed, the lengthy delay occurred despite the intense national interest in the disease and the fact that many countries have banned shipments of beef from the United States because of what they consider to be lax testing policies.

Until Friday, it was not public knowledge that an "experimental" test had been performed last November by a Department of Agriculture laboratory on the brain of a cow suspected of having mad cow disease, and that the test had come up positive.

For seven months, all that was known was that a test on the same cow done at the same laboratory at roughly the same time had come up negative. The negative result was obtained using a test that the Department of Agriculture refers to as its "gold standard."

The explanation that the Department of Agriculture gave late Friday, when the positive test result came to light, was that there was no bad intention or cover-up, and that the test in question was only experimental.