Tests have confirmed another case of mad cow disease in the United States since the first case was reported in December 2003, the US Department of Agriculture (USDA) announced Friday.

The second case, in a beef cow, was confirmed by an internationally recognized laboratory in Weybridge, England, Agriculture Secretary Mike Johanns said. The new tests were ordered after US tests produced conflicting results. The department also conducted more tests at its lab in Ames, Iowa.

Johanns stressed human health was not at risk.

"I am encouraged that our interlocking safeguards are working exactly as intended," 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 USDA said the confirmation of the new case of mad cow disease should not affect efforts to lift bans on US beef products in Japan and South Korea imposed after the first US mad cow disease in December 2003.

Japan, which used to be the largest importer of US beef, has said a confirmation of new case would not deter it from resuming beef imports. Japan agreed to reopen its market last fall but has failed to do so.

The new case was one of three suspected animals that had been previously tested negative for mad cow disease. They were tested again two weeks ago with a different technology at the request of the USDA's Inspector General who was reviewing the department's mad cow testing program. The results from a further test known as Western blot showed one animal tested positive. The conflicting test results prompted the department to seek verification.

Johanns said the USDA will integrate Western blot into its routine testing of mad cow disease.

The USDA said the animal newly confirmed to be infected with mad cow disease was at least eight years old. Like the first case, it was born before the United States and Canada banned the use of cattle parts in cattle feed, which is how the mad cow disease is believed to spread.

The first US confirmed case of mad cow disease was in a Washington state dairy cow imported from Canada.

USDA officials said the brain tissue samples from the new case appeared different from the classical form of mad cow disease seen in Britain. But it is classified as mad cow disease.

People eating animal meat products contaminated with mad cow disease, or bovine spongiform encephalopathy (BSE), can develop a human variant of the fatal brain-wasting disease, called Creutzfeldt-Jakob disease. The brain disorder has killed more than 150 people, mostly in Britain, where an outbreak was reported in the 1990s.

Source: Xinhua