Statement by USDA Chief Veterinary Officer John Clifford (DVM)
Regarding Positive BSE Test Results
March 13, 2006
“We received a positive result on a Western blot confirmatory test conducted at the USDA laboratories in Ames, Iowa, on samples from an animal that had tested “inconclusive” on a rapid screening test performed on Friday, March 10.
“The samples were taken from a non-ambulatory animal on a farm in Alabama. A local private veterinarian euthanized and sampled the animal and sent the samples for further testing, which was conducted at one of our contract diagnostic laboratories at the University of Georgia. The animal was buried on the farm and it did not enter the animal or human food chains.
“We are now working with Alabama animal health officials to conduct an epidemiological investigation to gather any further information we can on the herd of origin of this animal. The animal had only resided on the most recent farm in Alabama for less than a year.
“We will be working to locate animals from this cow’s birth cohort (animals born in the same herd within one year of the affected animal) and any offspring. We will also work with Food and Drug Administration officials to determine any feed history that may be relevant to the investigation. Experience worldwide has shown us that it is highly unusual to find BSE in more than one animal in a herd or in an affected animal’s offspring. Nevertheless, all animals of interest will be tested for BSE.
“Under USDA testing protocols, surveillance samples are sent to contract laboratories for screening tests. If the sample is found to be inconclusive on the screening test, it is then shipped to our National Veterinary Services Laboratories (NVSL) in Ames, Iowa, for an additional rapid test and two confirmatory tests: the immunohistochemistry (IHC) test, which is conducted by APHIS scientists, and the Western blot test, which is conducted by scientists with USDA’s Agricultural Research Service. USDA considers an animal positive for BSE if either of the two confirmatory tests returns a positive result.
“In this instance, the inconclusive result from the contract lab in Georgia was confirmed through a second rapid test at NVSL. Now, the Western blot test has returned a positive result, and that is sufficient for us to confirm this animal to be positive for BSE, which is why we are making this announcement today. The IHC results are still pending and we will release those results as soon as they are available, which we expect to be later this week.
“I want to emphasize that human and animal health in the United States are protected by a system of interlocking safeguards, and that we remain very confident in the safety of U.S. beef. Again, this animal did not enter the human food or animal feed chains.
“While epidemiological work to determine the animal’s precise age is just getting underway and is ongoing, the attending veterinarian has indicated that, based on dentition, it was an older animal, quite possibly upwards of 10 years of age. This would indicate that this animal would have been born prior to the implementation of the Food and Drug Administration’s 1997 feed ban. Older animals are more likely to have been exposed to contaminated feed circulating before the FDA’s 1997 ban on ruminant-to-ruminant feeding practices, which scientific research has indicated is the most likely route for BSE transmission.
“By any measure, the incidence of BSE in this country is extremely low. Our enhanced surveillance program was designed as a one-time snapshot to provide information about the level of prevalence of BSE in the United States. We have conducted surveillance in the United States since 1990 and following the initial positive in December 2003, we developed an enhanced surveillance program. Since June 2004, all sectors of the cattle industry have cooperated in this program by submitting samples from more than 650,000 animals from the highest risk populations and more than 20,000 from clinically normal, older animals, as part our enhanced BSE surveillance program. To date, including the animal in today’s announcement, only two of these highest risk animals have tested positive for the disease as part of the enhanced surveillance program.
“As we approach the conclusion of our enhanced surveillance program, let me offer a few thoughts regarding surveillance going forward. I can assure you that we will continue to base our maintenance surveillance testing on international guidelines. Though the nature and extent of maintenance surveillance has not yet been finalized, the incidence of BSE in this country remains extremely low and our interlocking safeguards are working to protect both human and animal health and we remain very confident in the safety of U.S. beef.
“As we move forward with the epidemiological investigation that has been initiated today into this case of BSE, we will continue to be very transparent in sharing information with the public and with our trading partners around the world.”