Officials with USDA announced on July 27 that the agency is conducting further BSE testing on tissue samples from a cow that generated non-definitive results. According to agency reports, the cow was at least 12 years old and died in April of complications during calving. A local veterinarian collected and preserved a brain sample at the time, but did not immediately submit the sample for analysis.
Dr. John Clifford, assistant deputy administrator of USDA’s Animal and Plant Health Inspection Service, says “It is important to note that this animal poses no threat to our food supply because it did not enter the human food or animal feed chains. “
USDA is conducting further testing at the National Veterinary Services Laboratories in Ames , Iowa , in consultation with experts from the international reference laboratory in Weybridge, England . The agency also has sent samples from the animal to the Weybridge laboratory for further testing.
Initial testing, using the immunohistochemistry test, produced the non-definitive result. Because of the preservative used on the sample, the laboratories are limited to using the IHC test, rather than the rapid screening test or the Western blot confirmatory test. Dr. Clifford notes that it is possible for the IHC test to yield differing results depending on the “slice” of tissue that is tested. Scientists at Ames and at Weybridge will run the IHC test on additional “slices” of tissue from this animal to determine whether or not it was infected with BSE. “We will announce results as soon as they are compiled, which we expect to occur by next week,” Dr. Clifford says.
“Regardless of the outcome of the further testing,” Dr. Clifford says, “I want to emphasize that human and animal health in the United States are protected by a system of interlocking safeguards. The most important of these is the ban on specified risk materials from the food supply and the Food and Drug Administration’s feed ban. And by any measure, the incidence of BSE in this country is extremely low.”