Purdue News

July 1, 2004

Mad cow rapid test a necessity, working on accuracy

WEST LAFAYETTE, Ind. – As a rapid testing program for mad cow disease continues to ramp up in the United States, false positives, like the one confirmed Wednesday (June 30), will continue to crop up, according to a Purdue University veterinary pathologist.

"The rapid test has two advantages: It's very quick, and large numbers of animals can be tested with automated equipment," said Leon Thacker, who also is director of the Indiana Disease Diagnostic Laboratory. "The disadvantage is that we're still trying to determine the precise cutoff figure for when a sample is positive, and that will take time to adjust."

Testing on a second sample detected this week continues.

Thacker says the rapid tests are necessary so that meat can be released quickly. He says it's common when implementing new testing procedures for it to take some time before the exact range of a positive sample is pinpointed. Since the stepped up testing began June 1, officials are working on what they assume is an accurate range.

The rapid tests are currently used by 12 sites around the country. However, Thacker says the "gold standard" for testing is still the immunohistochemistry tests done at the U.S. Department of Agriculture facility in Ames, Iowa. Those tests require extensive prep time for samples, and each sample result must be individually read by a pathologist.

Animals tested for bovine spongiform encephalopathy, commonly known as mad cow disease, include dead and non-ambulatory cattle, animals showing symptoms of the disease and all animals over 24 months of age.

CONTACT: Thacker, (765) 494-7460 (office), (765)-404-5829 (cell), thackerl@purdue.edu

Writer: Beth Forbes, (765) 494-2722, forbes@purdue.edu