News of the first known case of bovine spongiform encephalopathy (BSE, or “mad cow disease”) in the United States on December 23 shook the country's beef industry. But if ranchers were caught unaware, it wasn't because of a lack of available diagnostic procedures.

All testing for BSE now occurs postmortem, using tissue from the obex region of the brain stem. The most sensitive test, which is also the lengthiest, is the mouse bioassay, in which suspect brain tissue is injected into the brain of a mouse, and 6 months to 1 year later, the mouse is killed and its brain examined to see if it has developed disease. “Very conclusive ultimately, but not very rapid to say the least,” Brad Crutchfield, vice president of the life sciences group at Bio-Rad Laboratories, told The Scientist.

At the National Veterinary Services Laboratory, a US Department of Agriculture (USDA) testing facility...

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