By Jon Bonné
msnbc.com
updated 6/25/2004 9:07:00 PM ET 2004-06-26T01:07:00

A potential U.S. case of mad cow disease, found as part of a newly expanded testing program, was announced late Friday. If confirmed, it would be the second case of the disease discovered in this country.

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The U.S. Department of Agriculture announced an initial "inconclusive" finding from one of the rapid tests being given to samples from cattle considered by the government to be at highest risk for the fatal brain disease, which is formally known as bovine spongiform encephalopathy, or BSE.

USDA chief veterinarian John Clifford warned that the finding "does not mean we have found another case of BSE in this country."

As Clifford pointed out, the quick-turnaround tests used to check for mad cow can sometimes return a positive result because they are highly sensitive.

According to the guidelines for the new testing program, which began this month, any positive finding must be confirmed by the USDA's National Veterinary Services Laboratories in Ames, Iowa. The suspect sample, which the USDA said it was informed at about 5:30 p.m. ET Friday, will be sent to Ames for a confirmation using a far more accurate procedure that can take up to two weeks.

Clifford declined to provide details of how or where the cow was found, or even its age. "Because this test is only an inconclusive test result, and because of the chance the confirmatory results will be negative, we are not going to disclose that information at this time," he said.

While BSE has been detected in cattle as young as 20 months, it is more often found in cows over 30 months. Most U.S. cattle are slaughtered far younger than that, and the testing program is not designed to check younger cattle.

Mad cow is thought to cause a related, always-fatal disease in humans. 

The expanded tests were implemented after the first U.S. case was found last December, and largely based on the recommendations of an international panel of experts convened by Agriculture Secretary Ann Veneman.

While the USDA wouldn't set specific numbers of cattle to test, it hoped to examine the brains of at least 268,000 cows in the next 18 months. That would constitute more than half of the 446,000 animals it considers at risk for the disease, which occurs when deformed proteins begin to eat holes in an animal's brain. But the testing plan covers just a fraction of the 37 million cattle slaughtered in the United States each year.

More cases 'not a crisis'?
Almost everyone who has researched mad cow disease, including beef industry officials, believes a few additional cases are likely to appear in the course of the expanded testing. "To me, one, two, three, five other cases is not a crisis," William Hueston, a University of Minnesota veterinary epidemiologist and the sole U.S. member of Veneman's panel, told MSNBC.com in March.

But critics of the government's testing plans believe these efforts fall short. They point to other countries, where a far greater percentage of animals are tested; France, for example, tests more than half the cattle it slaughters for BSE. And they have criticized the USDA for its refusal earlier this year to allow private companies to conduct their own, more extensive tests for the disease.

Michael Hansen, who researches mad cow for Consumers Union, said the preliminary finding might spur officials to expand their testing program, which currently checks samples at seven state labs across the country.

"Hopefully, this will spur the government to start taking stronger actions," Hansen said.

Initial preparations by the labs had called for some 500 to 1,000 tests per week, but the USDA hasn't disclosed how many tests have been conducted so far.

The labs generally use a quick protocol known as Elisa, which destroys the normal forms of proteins known as prions, and leaves behind the abnormal ones that cause the disease. Elisa results can be obtained in a few hours, but must be confirmed by a far more elaborate process known as immunohistochemistry, which the Ames lab will perform on the current sample.

Clifford said the suspect cow had not entered the human food chain and reiterated that the "USDA remains confident in the safety of the U.S. beef supply."

He noted that food safety rules, like a ban on so-called specified risk materials (SRMs) from cattle over 30 months, remain effective measures to protect public health. SRMs include parts of the nervous system such as the brain and spinal cord, where the infectious proteins are most often found.

However, Veneman's own panel said in February that while the 30-month rule was a "reasonable temporary compromise," it believed the maximum age for SRMs should be lowered to 12 months until U.S. animals were proven to be at minimal risk.

And Hansen pointed out that changes announced in January by the Food and Drug Administration to its rules on cattle feed have yet to be implemented. The FDA's earlier 1997 ban on feeding cattle protein to other cows is considered one of the biggest steps to limiting the disease in this country.

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