Inconclusive BSE Case Tests Positive Using Western Blot
Test samples sent to England for further analysis.

June 13, 2005 — Secretary of Agriculture Mike Johanns announced late Friday evening that a U.S. animal that previously tested negative for bovine spongiform encephalopathy (BSE) November 2004 using an immunohistochemistry (IHC) test has tested positive using another internationally recognized test, the Western blot.

Of the more than 375,000 targeted animals tested since the U.S. Department of Agriculture’s (USDA’s) enhanced surveillance program began last June, three have resulted in inconclusive rapid tests. Although all three have since returned negative IHC results, Johanns explained, the USDA Inspector General, while reviewing the BSE surveillance system earlier last week, recommended to retest all three samples using the Western blot analysis. Of the three samples, two tested negative; however, the sample from the November animal was reactive, said John Clifford, Animal and Plant Health Inspection Service (APHIS) chief veterinary officer.

Due to the conflicting results of the IHC and Western blot tests, Clifford said, a sample from the animal will be sent to the World Organization for Animal Health (OIE)-recognized reference laboratory in Weybridge, England.

“The reason we’re sending this to Weybridge is because we feel this is an unusual case, and we’d like to have the assistance of an internationally recognized laboratory for BSE,” Clifford stated during a press conference.

The aged animal was of a beef breed and was a downer, Clifford reported. Both USDA officials were quick to point out that the animal did not enter the feed or human food chain and, therefore, presents no human health risk.

Clifford reported that in this instance, the test could be considered a weak positive test since they had to enhance or enrich the sample by using a larger sample size and concentrating the abnormal protein to achieve the outcome. He said the unusualness of the case will require additional testing before a BSE diagnosis is made.

In addition to testing at the England laboratory, USDA will conduct further tests, which will take several days to complete, Clifford announced.

Johanns said the findings shouldn’t have any effect on international trade relations since the suspected animal was aged.

“Our discussions with Japan have related to 20-month animals, as you know. Our discussions with Korea have related to 30-month animals, and the rule relative to Canada, or the Minimal Risk Rule in general I should say, relates to animals under 30 months and meat product under 30 months,” Johanns said. “So, I really don’t believe this has any impact on our international trading partners. We’ll be working with them to get information in their hands and make sure that they understand the situation.”

For more information visit www.usda.gov.



— by Crystal Albers, Angus Productions Inc. assistant editor


© Copyright 2005 Angus Productions Inc.

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