"This is the first confirmed case resulting from our surveillance of cows going for slaughter in the United States,” Agriculture Secretary Mike Johanns said. "This animal was blocked from entering the food supply because of the firewalls we have in place. Americans have every reason to continue to be confident in the safety of our beef."

The cow involved was termed as a "downer," or nonambulatory cow. It thus had been prohibited from entering the food supply chain by a USDA food-safety rule.