At the recommendation of the USDA’s Office of the Inspector General, three animals that tested negative for BSE last fall have been retested using the SAF immunoblot test, also called the Western blot test. Of the three samples, two were negative, but the third – the one that had previously had a strong reaction to the rapid test – came back positive. USDA received the results late Friday.
Each of the three animals had previously had an inconclusive test result from a rapid screening test and then was retested using an immunohistochemistry (IHC) test. All three IHC tests were negative. Both the IHC test and the Western blot test are internationally recognized confirmatory tests for the diagnosis of bovine spongiform encephalopathy.
Former Secretary Ann Veneman had asked the Inspector General to conduct an impartial review of all USDA BSE-related activities in order to determine if programs could be improved, and if the BSE-surveillance program was reaching the targeted cattle population. The IG has been working with the Animal and Plant Health Inspection Service, the Food Safety and Inspection Service and the Agricultural Research Service in this review. The additional testing was requested because originally, one of the samples had yielded a strong reaction to the rapid test, but then was negative in the IHC test.
"Because of the conflicting results on the IHC and Western blot tests, a sample from this animal will be sent to the OIE-recognized reference laboratory for BSE in Weybridge, England,” says John Clifford, chief veterinary officer APHIS. “USDA will also be conducting further testing. Results are expected within two weeks.
No part of this animal ever entered the food chain. It was a non-ambulatory or downer animal and was removed from the food supply. It was processed at a facility that handles only animals unsuitable for human consumption, and the carcass was incinerated. APHIS officials did retain part of the brainstem at the National Veterinary Services Laboratory in Ames, Iowa in case further testing or research was needed.
So far, USDA's enhanced surveillance program has tested 375,000 animals for BSE. This program was designed to provide information about the level of prevalence of BSE in the United States.
“Since the inception of this program, we have fully anticipated the possibility that additional cases of BSE would be found,” says Clifford. “And, in fact, we are extremely gratified that to date, more than 375,000 animals have been tested for the disease and, with the exception of the conflicting results we have received on this one animal, all have ultimately proven to be negative for the disease.”
If you would like to view the transcript of Friday’s announcement, as well as the question-and-answers session afterward, go to www.usda.gov/wps/portal/!ut/p/_s.7_0_A/7_0_1OB?contentidonly=true&contentid=2005/06/0207.xml