A cow in the southern state of Alabama has tested positive for mad cow disease. It is the third case ever found in the United States.

Officials with the state of Alabama say random testing has confirmed the presence of bovine spongiform encephalopathy, BSE, in a cow in the state. It is only the third case of the brain-wasting disease in the United States since the first case in December 2003. One case was imported from Canada. The other was reported in Texas last summer.

In Alabama, State Veterinarian Dr. Tony Frazier said the illness was detected in the brain tissue of a cow that had been sick and was not able to stand - what is known in the cattle industry as a downer. The animal failed to respond to treatment and was euthanized. "The physical exam by the attending veterinarian was that she was a downer. That's another important point because another firewall that's in place is that downer animals are not allowed into the food chain, so she could not have gone to slaughter," he said.

The cow was tested as part of routine surveillance for the disease. The United States Department of Agriculture says more than 660,000 cattle have been tested for BSE during the past two years.

Alabama State Health Officer Dr. Donald Williamson said there was no threat to human or animal health. "The animal never got in the food chain. The absence of the animal in the food chain then means that from this cow, the citizens of Alabama have no reason to think the beef supply is in any way unsafe. It is absolutely as safe today as it was yesterday as it will be tomorrow," he said.

The cow, which had been on the Alabama farm for about a year, was at least 10 years old. Officials said it could have become contaminated before 1997, when the U.S. Food and Drug Administration prohibited the use of cattle feeds containing protein from mammals that might carry BSE.