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23 November 2004
Tests for Mad Cow Disease Negative, Agriculture Dept. Says
USDA testing rules out possible case of bovine spongiform encephalopathy
A cow for which preliminary tests for bovine spongiform encephalopathy (BSE, commonly known as "mad cow disease") had proved inconclusive has been determined free of the disease, the U.S. Department of Agriculture (USDA) announced November 23.
USDA said the National Veterinary Services Laboratories (NVSL) in Ames, Iowa, tested the inconclusive screening sample and found it negative for BSE.
In order to be absolutely certain of the results, and mindful of the two inclusive preliminary screening tests, the NVSL ran the immunohistochemistry (IHC) test twice, once on November 22 and again on November 23. Both times, the test was negative for BSE, the agency said.
USDA described the IHC test as "an internationally-recognized gold standard test for BSE."
The agency also explained that the screening tests are deliberately designed to flag samples in which there is even the slightest possibility of BSE infection.
"APHIS [USDA's Animal and Plant Health Inspection Service] began an enhanced surveillance program on June 1 and to date has tested over 121,000 samples for BSE. Screening tests are designed to be extremely sensitive and false positives are not unexpected, " USDA said.
Following is the text of the USDA statement:
(begin text)
U.S. Department of Agriculture
[Washington. D.C.]
STATEMENT BY JOHN CLIFFORD, DEPUTY ADMINISTRATOR
ANIMAL & PLANT HEALTH INSPECTION SERVICE
November 23, 2004
"The USDA National Veterinary Services Laboratories (NVSL) in Ames, Iowa, has determined that the inconclusive screening test sample reported on Nov. 18 has tested negative for BSE upon confirmatory testing.
"The Nov. 18 sample is the first that has tested inconclusive under an APHIS protocol announced in August that calls for public reporting of screening results only after two reactive screens. NVSL used the immunohistochemistry (IHC) test, an internationally-recognized gold standard test for BSE, and received a negative result on Nov. 22.
Because the Nov. 18 screening test results were reactive in both the first and second screens, NVSL scientists made the recommendation to run the IHC test a second time. On Nov. 23 they reported the second IHC test was negative. Negative results from both IHC tests makes us confident that the animal in question is indeed negative for BSE.
"APHIS began an enhanced surveillance program on June 1 and to date has tested over 121,000 samples for BSE. Screening tests are designed to be extremely sensitive and false positives are not unexpected. APHIS has reported three inconclusives including the Nov. 18 sample and all have tested negative on confirmatory testing."
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(Distributed by the Bureau of International Information Programs, U.S. Department of State. Web site: http://usinfo.state.gov)
