SAN FRANCISCO — The California dairy cow found to have mad cow disease had been euthanized after it became lame and started lying down, federal officials revealed in their latest update on the discovery.
The U.S. Department of Agriculture also said Thursday that the animal was 10 years and seven months old.
A spokesman for U.S. Rep. Devin Nunes, of California, had said Wednesday that the sick cow was 5 years old. It came from a dairy farm in Tulare County, the nation's No. 1 dairy-producing county.
The USDA didn't elaborate on the cow's symptoms other than to say it was “humanely euthanized after it developed lameness and became recumbent.” Outward signs of the disease can include unsteadiness and lack of coordination.
Routine testing at a transfer facility showed the dead Holstein, which was destined for a rendering plant, had mad cow disease, or bovine spongiform encephalopathy. It was the fourth case of mad cow disease ever discovered in the U.S.
Animals at greater risk for the disease include those with symptoms of neurological disease, “downer” animals at slaughterhouses, animals that die at dairies or cattle ranches for unknown reasons, and cows more than 2½ years old, because BSE occurs in older cows.
U.S. health officials said there is no risk to the food supply. The California cow was never destined for the meat market, and it developed “atypical” BSE from a random mutation, something that scientists know happens occasionally. Somehow, a protein the body normally harbors folds into an abnormal shape called a prion, setting off a chain reaction of misfolds that eventually kills brain cells.