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The U.S. Department of Agriculture today confirmed a case of mad cow disease found in a dairy cow in central California.

In a press briefing Tuesday afternoon, John Clifford, the USDA's chief veterinary officer, said the cow's meat did not enter the food supply and the carcass will be destroyed. The animal was found at a rendering facility.

"There is really no concern for alarm here with regards to this animal," Clifford said. "Both human health and animal health are protected with regards to this issue."

According to a statement from USDA, milk does not transmit mad cow disease.

This is the fourth case of mad cow disease in the U.S. cattle supply since December 2003. The most recent case occurred in 2006, when officials discovered an infected cow on an Alabama farm.

The case was discovered as part of the USDA's regular surveillance program of U.S. cattle. No other cases have been reported yet, and Dr. William Schaffner, chair of preventive medicine at Vanderbilt University, said it's unlikely that more cows will be infected.

"Mad cow occurs in animals as it does in humans - rarely and sporadically. At this point, I would not expect there to be another cow to be found," he said.

Mad cow disease affects the brain and spine of an animal, the result of an unusual transmissible protein called a prion, according to the U.S Centers for Disease Control and Prevention. Those body parts are kept out of grocery stores and restaurants and have no contact with the meat that does make its way to consumers.

No humans have ever been infected with mad cow disease in the U.S., but fears of the disease became prominent in the 1990s when nearly 150 people in Britain died from the brain-wasting disease.