First U.S. mad cow case since '06 found

WASHINGTON -- The first new case of mad cow disease in the United States since 2006 has been discovered in a dairy cow in California, but health authorities said yesterday the animal never was a threat to the nation's food supply.

The infected cow, the fourth ever discovered in the United States, was found as part of an Agriculture Department surveillance program that tests 40,000 cows a year for the fatal brain disease.

No meat from the cow was bound for the food supply, said John Clifford, the department's chief veterinary officer. "There is really no cause for alarm here with regard to this animal," he said.

Mad cow disease, or bovine spongiform encephalopathy (BSE), is fatal to cows and can cause a fatal brain disease in humans who eat tainted beef. The World Health Organization says tests show humans cannot be infected by drinking milk from BSE-infected cows.

Following a huge outbreak in the United Kingdom that peaked in 1993, the United States intensified precautions to keep BSE out of U.S. cattle and the food supply. In other countries, the infection's spread was blamed on farmers adding recycled meat and bone meal from infected cows into cattle feed, so a key U.S. step has been to ban feed containing such material.

Clifford said the California cow is what scientists call an atypical case of BSE, meaning it didn't get the disease from eating infected cattle feed, which is important.

It's "just a random mutation that can happen every once in a great while in an animal," said Bruce Akey of the New York Veterinary Diagnostic Laboratory at Cornell University. "Random mutations go on in nature all the time."

The testing system worked because it caught what is a really rare event, added Mike Doyle, director of the University of Georgia's Center for Food Safety.