Definitive testing has ruled out mad cow disease in an animal that federal officials had identified last week as a potential carrier, officials said yesterday.
The result cheered the beef industry, which had braced itself to hear that a second case of mad cow disease had been discovered in the United States. The first case was discovered in December in Washington state.
_____Mad Cow Disease_____
Agriculture Dept. Investigates Possible Mad Cow Case (Associated Press, Nov 18, 2004)
Japan to Accept U.S. Beef Again (The Washington Post, Oct 24, 2004)
Keeping Mad Cow Out of Cosmetics (The Washington Post, Oct 19, 2004)
Blood Transfusion Linked to 2nd Human Case of Mad Cow (The Washington Post, Aug 6, 2004)
Errors Found in USDA Mad Cow Identification (The Washington Post, Jul 15, 2004)
The Agriculture Department said scientists had carried out the test at the National Veterinary Services Laboratories in Ames, Iowa -- and repeated it a second time to be sure.
In a statement late yesterday afternoon, John Clifford, deputy administrator at USDA's Animal and Plant Health Inspection Service, said the negative result first became known Monday. But because two preliminary tests had raised a suspicion of mad cow infection, scientists asked to run a second immunohistochemistry test, he said. The result from that test became available yesterday.
"We feel very confident that it is negative," Clifford said in an interview.
"Negative? I'm surprised," said David Ropeik, who has closely followed the case as director of risk communication at the Harvard Center for Risk Analysis, which has studied the potential impact of mad cow disease in the United States.
Ropeik had previously said that the fact that two preliminary tests had raised red flags about the meat sample suggested it was likely to be positive for the disease. "It is going to be a quieter Thanksgiving," he said.
The news is certain to relieve workers in the beef industry, which is still recovering after the discovery of the first U.S. case of mad cow disease, in an animal that came originally from Canada. U.S. beef exports came to a virtual standstill, and many of the resulting trade barriers have yet to be lifted.
Clifford said he did not expect the negative finding to affect trade. In conversations with countries that import U.S. beef, he said, foreign officials had made clear that the discovery of one or two cases of mad cow disease in the United States would not lead them to conclude that U.S. beef is dangerous.
Mad cow disease is known to cause a brain-wasting disease in some people who eat infected beef, but various experts argue that even if there are a few diseased animals in the United States, the public health is not at risk because of safety measures that prevent potentially infectious tissue from reaching consumers or being added to the feed given to other cattle.
When the Ames lab found evidence of mad cow disease last year in a tissue sample from a Holstein in Washington state, Ropeik noted, officials sent tissue samples for confirmatory tests to a reference lab in the United Kingdom, which he called "the 24-karat-gold standard." He described the Iowa lab as "reliable . . . the 18-karat-gold standard."
Ropeik said he saw no reason for additional testing this time, and Clifford said USDA has no plans to conduct further tests.
The USDA official said the cow in question had been incinerated and none of its tissues had entered the human food supply or the animal feed chain. Apart from identifying the animal as a cow, officials did not provide any details, such as its location or age.
Carol Tucker Foreman of the Consumer Federation of America, a nonprofit consumer advocacy group, said that although the good news was a relief, USDA "rules don't cover all potentially hazardous tissues, don't protect against cross contamination and aren't adequately enforced." She called on the agency and the Food and Drug Administration to strengthen safety policies and step up enforcement.