Late Tuesday USDA received non-definitive test results on an animal sampled as part of a voluntary extension of the enhanced BSE surveillance program, according to a statement from Animal Plant and Health Inspection Service Chief Veterinarian Dr. John Clifford.
The sample was submitted by a private veterinarian who treated the sample with a preservative, which readies it for testing using the immunohistochemistry (IHC) test - an internationally recognized confirmatory test for BSE. Neither the rapid screening test nor the Western blot confirmatory test can be conducted on a sample that has been preserved.
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. Clifford says samples from this animal are also being sent to the Weybridge laboratory for further testing.
"Our laboratory ran the IHC test on the sample and received non-definitive results that suggest the need for further testing," Clifford says. "As we have previously experienced, it is possible for an IHC test to yield differing results depending on the 'slice' of tissue that is tested. Therefore, scientists at our laboratory 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."
The sample in question was taken from a cow that was at least 12 years of age and experienced complications during calving. The sample was taken in April, at which time the protocols allow for a preservative to be used (protocols changed in June 2005).
"The sample was not submitted to us until last week, because the veterinarian set aside the sample after preserving it and simply forgot to send it in," Clifford explains. "The carcass of this animal was destroyed, therefore there is absolutely no risk to human or animal health from this animal."
Clifford says USDA will announce results as soon as they are compiled, which the agency expects to occur by next week.