The WaPo has summarized the unbelievable move by the USDA to block Mad Cow testing by a U.S. beef exporter. Incredibly, the USDA admits exactly what is going on:
USDA officials say that they sympathize with Creekstone and similar operations hurt by the bans imposed by Japan and other nations, but that agreeing to the company's request could imply there is a safety issue with American beef and usher in an era of expensive testing...[t]he issue is not the effectiveness of the testing itself, as Creekstone would be working under the auspices of an academic lab that the USDA has approved for mad cow testing. Rather, the agency objects to the very idea of testing every animal, including younger ones.
The USDA strenuously argues that there is "no scientific justification" for the testing--based on the new testing program that will test only older animals with a total count of some 200,000 animals. That's out of 30,000,000 cattle slaughtered each year in the U.S., less than 1% of the total stock. These kinds of models rely heavily on the notion that the disease is tightly geographically bound, but since the cause of the disease may be due to feed that is nationally distributed, I think it's clear that the USDA is simply burying its head in the ground.