Statement by Dr. John Clifford Regarding Non-Definitive BSE Test Results
Late yesterday, we received non-definitive test results on an animal sampled as part of a voluntary extension of our enhanced BSE surveillance program. 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. We are also sending samples from this animal to the Weybridge laboratory for further testing. 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.
The sample was submitted to us by a private veterinarian. As an extension of our enhanced surveillance program, accredited private veterinarians, who often visit farms in remote areas, collect samples when warranted. The sample in question today was taken from a cow that was at least 12 years of age and experienced complications during calving. The veterinarian 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.
Our laboratory ran the IHC test on the sample and received non-definitive results that suggest the need for further testing. 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. We will announce results as soon as they are compiled, which we expect to occur by next week.
I would note that the sample was taken in April, at which time the protocols allowed 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. On that point, I would like to emphasize that while that time lag is not optimal, it has no implications in terms of the risk to human health. The carcass of this animal was destroyed, therefore there is absolutely no risk to human or animal health from this animal.
Regardless of the outcome of the further testing, 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. Our enhanced surveillance program is designed to provide information about the level of prevalence of BSE in the United States. We are extremely gratified that to date, all sectors of the cattle industry have cooperated in this program by submitting samples from more than 419,000 animals from the highest risk populations. To date, only one animal has tested positive for the disease as part of the surveillance program. These interlocking safeguards continue to protect our food supply.