WASHINGTON -- Exhaustive tests have confirmed mad cow disease in an animal apparently born in the United States, officials said Friday. It is the second case of the disease confirmed in this country, but Agriculture Secretary Mike Johanns stressed there was no threat to public health.
The animal, a "downer" that could not walk, was not killed at a slaughterhouse but at a rendering plant for animals unfit for human consumption, officials said. Johanns would not say where the case turned up, but he said there was no evidence the cow was imported.
"I am encouraged that our interlocking safeguards are working exactly as intended," Johanns said at a news conference. "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 Agriculture Department said the news also should not affect efforts to lift bans on U.S. beef in Japan and Korea imposed after the first U.S. case in December 2003. Officials in Japan, formerly the largest customer of U.S. beef, have said a positive test result would not deter them from resuming beef imports. Japan agreed to reopen its market last fall but has not actually lifted its ban.
An internationally recognized laboratory in Weybridge, England, confirmed the case Friday after U.S. tests produced conflicting results, Johanns said. Initial screening had indicated the presence of the disease, but the animal was tested and cleared of having the brain-wasting illness.
New tests were ordered two weeks ago. Those results, from a test known as the Western blot, came back positive, leading officials to seek confirmation from the Weybridge lab. The department also performed more tests at its lab in Ames, Iowa.
Mad cow disease kills brain cells and leaves spongy holes behind. It has been linked to the consumption of contaminated meat. The disease has killed about 150 people worldwide.
, mostly in Britain.
The first case of mad cow disease in the United States was confirmed in December 2003. It turned up in Washington state in a dairy cow imported from Canada.
The new case was in an animal at least 8 years old, the department said. Like the first case, it was born before the United States and Canada banned cattle parts in cattle feed, which is how the disease is believed to spread.
Officials said the brain tissue samples appeared different from the classical form of mad cow disease seen in Britain, where there was an outbreak in the 1990s, but they are classifying it as mad cow disease, anyway.
Johanns said his department will start conducting the more sensitive Western blot test as a matter of routine. The department has been criticized by consumer groups and cattlemen for not resolving conflicting test results on this animal last November.
The department did initial screening using a "rapid test," which was positive. A more detailed immunohistochemistry, or IHC test, was negative. But the department did not conduct a third round, using the Western blot, until the department's inspector general ordered it to do so two weeks ago, said USDA officials, including the inspector general.
Now the department will use both IHC and Western blot when rapid tests indicate the presence of the disease, Johanns said.
"By adding the second confirmatory test, we boost that confidence and bring our testing in line with the evolving worldwide trend," he said.
U.S. officials escalated testing for the disease after the first U.S. case. More than 388,000 dead cattle have been screened in the past 13 months, compared with about 2,000 screenings annually before the first case.
Earlier in the day, Johanns expressed irritation that the new round of testing had been ordered without his knowledge or approval. Inspector General Phyllis Fong, an internal auditor and investigator, has not explained why she ordered the new tests.
"I was asked by the Senate and the president to operate the department," Johanns told reporters Friday morning. "I believe, in this area, very clearly, the secretary should be consulted, whoever the secretary is, before testing is undertaken. From my standpoint, I believe I was put there to operate the department and was very disappointed."
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