New case of mad cow disease in California

The first new case of mad cow disease in the U.S. since 2006 has been discovered in a dairy cow in California, but health authorities said the animal never posed a threat to the nation's food supply.     

The infected cow, the fourth ever discovered in the U.S., was found as part of an Agriculture Department surveillance program that tests about 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," Clifford told reporters at a hastily convened news conference.     

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

In the wake of a massive outbreak in Britain that peaked in 1993, the U.S. 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 that it didn't get the disease from eating infected cattle feed, which is important.     

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

Questions remain about whether the incident will prompt the USDA to change how it tests for the disease. But Mike Doyle, director of the University of Georgia's Center for Food Safety, said the testing system worked because it caught what is a really rare event.     

AP