Tests confirmed a second case of mad cow disease in the United States, this time in an 8-year-old beef cow, the US Agriculture Department (USDA) said.
The USDA said it was investigating where the animal with the brain-wasting disease originally came from and was still doing DNA testing to confirm its herd. There was no evidence it was an imported animal.
Meat from the infected cow was not sold to consumers or as animal feed, US Agriculture Secretary Mike Johanns told a news conference, defending the country's current safeguards. The previous US confirmed case of mad cow disease, or bovine spongiform encephalopathy (BSE), was found in December 2003 in a Washington state dairy cow.
"The BSE threat to humans in this country is so remote that there's a better chance you'll get hurt crossing the street to get to the grocery store than by the beef you buy in the grocery store," Mr Johanns said. "The presence of the disease is extremely low in the United States," he said. "Our safeguards are working exactly as they should."
Ron DeHaven, head of the USDA's Animal and Plant Health Inspection, told a panel discussion at the Chicago Mercantile Exchange that the animal was an 8-year-old beef cow found at a pet food plant. Neither official would identify the state where the animal came from. Several published reports have said the infected cow was in Texas when it was sent to slaughter last November.
The second case of US case of mad cow disease first surfaced on June 10th, when it was revealed that the November case was reopened and the animal had tested positive for the brain-wasting disease after initially returning inconclusive results.
Mr Johanns said he directed USDA scientists to develop a new protocol to deal with "inconclusive" screening tests for BSE. He said the USDA would analyze how carcasses of suspect animals are segregated and stored while being tested. The first case of the deadly disease 18 months ago halted billions of dollars worth of American beef exports and raised questions about the safety of the US food supply.
Japan, formerly the biggest buyer of American beef, and South Korea, the third-largest, banned US shipments after the United States confirmed its only case of mad cow disease. Taiwan recently said it would reinstate a ban on US beef if a second case was confirmed.
Mr Johanns said he did not think ongoing discussions with Japan to reopen beef trade would be affected by the latest case. A Japanese farm ministry official said even if the United States confirmed a second case, the ministry would stick to taking steps to resume some imports of American beef.