The U.S. Department of Agriculture said Wednesday afternoon that tests indicate that mad cow disease may have been present in a 12-year-old cow that died from complications during calving.

The cow’s carcass was destroyed and the cow posed no threat to either the human or pet food supply because it never entered the food chain, the USDA’s chief veterinarian, Dr. John Clifford said.

The cow died on the farm where it lived, but officials did not say where the farm is.

A private veterinarian took a tissue sample from the animal in April as part of the USDA’s enhanced surveillance program, but didn’t submit the sample to the agency until last week, Clifford said.

The delay didn’t compromise the sample, Clifford said.

“The sample was not submitted to us until last week, because the veterinarian set aside the sample after preserving it and simply forgot to send it in,” he said.

“On that point, I would like to emphasize that while that time lag is not optimal, it has no implications in terms of the risk to human health,” he said.

Clifford says the Agriculture Department is going to conduct more tests and a brain tissue sample is being sent to a lab in England for testing.

Two other cases of the brain-wasting disease have been confirmed in the U.S.

One was confirmed last month in Texas cow that died and was delivered dead in November to a pet food plant in Waco.

The other was in a Canadian-born cow found in Washington State in 2003.

The quarantine was lifted earlier this month on the Texas ranch that produced the first native case of mad cow disease in the U.S. after tests on 67 animals came back negative for the disease.

Those specific cattle were tested because of their age proximity to the dead cow that was delivered dead to a Waco pet food plant last fall.

Twenty-nine adult cows from the herd were killed and were tested for the disease. The animals were born the year before and the year after the birth of the infected cow.

The herd was placed under a “hold order” on June 10 after the nation's first native case of mad cow disease was traced back to the 12-year-old cow that was dead when it arrived last fall at the Champion Pet Foods plant in Waco.

Champion Pet Foods, which makes several blends of dog food primarily for the Greyhound industry, began testing all dead and “downer” cattle for mad cow disease last year as part of the testing program of the U.S. Department of Agriculture, plant owner Benjy Bauer said in a prepared statement.

A tissue sample from the cow was sent to a laboratory at Texas A&M where initial tests for mad cow were inconclusive.

Meanwhile a USDA representative took the cow’s carcass to the Texas Veterinary Diagnostic Lab at A&M where it was incinerated, Bauer said.

The results of a second test were positive and the results of a third test performed in England confirmed the animal had mad cow disease, government officials announced on Friday.

Mad cow disease is the common term for bovine spongiform encephalopathy or BSE, a brain-wasting illness that infects cattle.

Scientists believe it spreads when a cow eats meal that contains spinal or brain tissue of an animal infected with BSE.

Humans can get a related illness called Creutzfeldt-Jakob disease if they eat meat containing infected tissue.

The incurable disease attacks the nervous system.

More than 150 people died of variant Creutzfeldt-Jakob disease in Europe after mad cow disease appeared in Britain in the 1980s and 1990s and spread to several other countries.

The United States has acted to guard against the disease.

Since 1997, the Food and Drug Administration has banned animal feed containing brain and spinal tissue of cattle.

Farmers used to feed such meal to their cattle because it was high in protein and could help the animals gain weight.

The U.S. also bans "downer" cows that can't walk from being processed for human food.

The government also requires removal of the brain, spinal column and other nerve tissues from cattle older than 30 months when they're slaughtered to keep them from entering the food supply.

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