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USDA Test for Mad Cow Disease Prove Inconclusive

Posted on: Thursday, 28 July 2005, 15:00 CDT

Jul. 28--The federal government said Wednesday that tests for mad cow disease were inconclusive on brain samples from a 12-year-old cow, so the samples will be sent to England for tests that will establish whether it had the illness.

Federal agriculture officials said they expected definitive results next week from a sample that a private veterinarian took in April but did not mail to a testing laboratory until July.

The delayed findings represent another odd twist for a program that has tested nearly 420,000 cows in 13 months but has come under criticism for inconsistent methods and results.

"The fellow took a sample in April, fixed it with formalin, put it in a box to ship and forgot it," said Jim Rogers, a U.S. Department of Agriculture spokesman.

The USDA had allowed vets to preserve and send in brain samples, but in June, after a second case of mad cow was discovered in the United States, they began requiring that samples be sent within 48 hours.

The cow was euthanized after complications during calving and never entered any food supply, Rogers said.

Scientists believe a 12-year-old cow could have gotten the brain-wasting bovine spongiform encephalopathy disease by eating the remains of infected cattle or scrapie-infected sheep present in cattle feed before the U.S. banned the feeding practice in 1997.

The USDA, following procedures used during the first two mad cow cases, declined to name the cow's home state, confirming only that it came from a ranch in a remote location.

"We're calling it nondefinitive," Rogers said of test results received late Tuesday at one of seven national laboratories that do initial screenings of brain samples. Testing of the newest sample will continue at the government's National Veterinary Services Laboratory in Ames, Iowa, as well as in England, he said.

The USDA notifies the public whenever an inconclusive sample is found. Twice last year, inconclusive results were later deemed negative. So far, only two cows in the United States have tested positive for the disease. Agriculture officials last month confirmed the disease in a cow near Lubbock, Texas, and one case was found in Mabton, Wash., in December 2003.

BSE has infected more than 183,000 cows in Great Britain and spread to more than 21 countries globally. People can contract a human form of the disease, new variant Creutzfeldt-Jakob, after eating certain parts of an infected cow.

More than 170 people around the world have been infected, mostly in Great Britain. The disease is always fatal.

While the outcome of the newest animal case remains unknown, the incident again renewed calls by critics of the meat industry to test more of the 34 million cattle slaughtered yearly for human consumption and to tighten feeding practices that some say can spread the disease further in the nation's 95 million cattle.

"We must follow the lead of the EU countries, Japan and others by instituting a complete ban on feeding animal protein to livestock, and we must safety-test millions of cattle before consumption," said John Stauber, coauthor of the 1997 book, "Mad Cow USA."

Agriculture Department officials also again assured consumers about the safety of the nation's beef supply and the adequacy of its testing program.

"We've said from the beginning we expected to find more cases," said Rogers. "That's the whole point of this operation. But finding another case doesn't mean a thing for food safety, because protocols are in place," he said, to keep high-risk brains and nervous system materials out of the food supply and to ban certain slaughter techniques.

"That's what protects consumers," Rogers said.

Tuesday's case confounded new testing procedures established by USDA last month to prevent a repeat of the last incident, in which tests on the Texas animal yielded inconclusive, then negative, and finally positive results at an international reference laboratory in Weybridge, England.

Because the brain sample was treated with the preservative formalin, officials said, it could not be tested using standard procedures. Ordinarily, it would have undergone an initial rapid test and, if it was inconclusive, the confirmatory Western blot and immunohistochemistry test. In this case, only the IHC test could be used, said Dr. John Clifford, chief veterinarian of USDA's Animal and Plant Health Inspection Service.

Clifford said it is possible for an IHC test to show different results depending on what slice of tissue it analyzes.

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Source: The Sacramento Bee

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