New mad cow case likely, experts say

WASHINGTON (Reuters) -- A final test is likely to confirm a second U.S. case of mad cow disease, experts said on Thursday, though they see a small possibility the animal, which tested "inconclusive" in two preliminary tests, could be given a clean bill of health.

The U.S. Agriculture Department said earlier on Thursday the animal tested "inconclusive" for mad cow disease in two rapid screening tests and that it would conduct more sophisticated analysis for confirmation. This was the first time two preliminary tests on the same animal returned inconclusive since the USDA began its rapid testing program on June 1.

The USDA said it would use a more sophisticated test, known as the immunohistochemistry test, or IHC, to confirm whether there is a new case of mad cow disease. Test results were expected in four to seven days.

"After two inconclusive results, you have a much higher rate of confirming (mad cow disease) to the IHC test," Brad Crutchfield, vice president of California-based Bio-Rad, told Reuters in an interview.

All the rapid screening tests used by USDA labs are from Bio-Rad Laboratories. The company calls an inconclusive finding a reactive test because it reacts to the BSE-specific prion protein.

"Greater than 95 percent of all doubly reactive tests are ultimately confirmed (to have mad cow disease)," Crutchfield said.

For every 240,000 double positive tests, Bio-Rad said one was a false positive after more sophisticated testing.

Barb Powers, director of Colorado State University's Veterinary Diagnostic Laboratory, said it was rare not to have a mad cow case confirmed after two inconclusive results.

However, a false positive in the final test was possible. Statistically, Powers said a false positive could be expected after testing one in 100,000 animals for mad cow disease. The USDA has tested more than 113,000 since June.

USDA declined to comment on the likelihood this would be a mad cow case. "They are inconclusive for the very reason that we just don't know," said USDA spokeswoman Alisa Harrison.

Live cattle futures at the Chicago Mercantile Exchange closed sharply lower. The December live cattle contract (LCZ4) settled off 2.700 cents per pound at 84.625.

Traders said this inconclusive test was so negative for the market because it was the first time two preliminary tests were inconclusive for the same animal.

"Thus far every time they have had an inconclusive, the second test has negated it," said Bob Wilson, analyst with the livestock consulting firm HedgersEdge.com. "This time the inconclusive sample was tested a second time and it was still inconclusive."

In August, the USDA said it would repeat a screening test twice before announcing an inconclusive result after finding two false positives last summer. Before then, the USDA announced inconclusive results after a single test.

Bio-Rad said human error was the likely cause of those two false positives. The tests are extremely sensitive and can produce false results if the brain samples are prepared improperly.

Animal health officials have used Bio-Rad's tests for more than six months, sampling more than 113,000 animals.

"At these seven laboratories, USDA has highly trained and highly competent people," Crutchfield said.