Washington ? The latest confirmed case of mad cow disease in the United States has been traced to a beef cow born in Texas 12 years ago and slaughtered last November at pet-food plant, Agriculture Department officials said Wednesday.

It was the first time the disease has been confirmed in a U.S.-born cow. The other U.S. case, confirmed in December 2003 in Washington state, was in a dairy cow imported from Canada.

The department’s chief veterinarian, Dr. John Clifford, said the new case was identified and linked to the herd in Texas through DNA testing. He said the herd had been quarantined and that none of the infected animal’s carcass entered the food or animal feed chain.

“The animal did not enter the human food chain. The safety of our food supply is not in question,” Clifford said in conference call with reporters. He said the government would not identify the cow’s owner or the town it came from. It was born and raised on the same farm, he said.

Eating the brain and other nervous tissue of an animal with the brain-wasting ailment is the only way the disease is known to spread.