First Inconclusive BSE Test Officially Negative

USDA says screening test was a false positive. Tuesday's inconclusive confirmatory results will not be released until next week. Jacqui Fatka

Published on: Jun 30, 2004

The USDA is trying to be as transparent as possible, although details made official remain slim. On Wednesday afternoon, new Chief Veterinary Officer John Clifford officially announced that the "inconclusive" screening result from an animal tested Friday, June 25 came back negative for bovine spongiform encephalopathy (BSE) after an immunohistochemistry (IHC) test was conducted.

Ironically the USDA decided to release inconclusive screen test results to prevent the market from being disrupted greatly. However, prices have been down near limit levels for the live and feeder cattle markets. Clifford explains that USDA's goal is to be very transparent and open to prevent rumors in the trading pits.

"Because we have a test and hold procedure with samples sent to the National Veterinary Laboratory Service, we realize the information may be leaked," he says. "We want to be minimize impact on market. After we get this information out there a couple of times, our hope is it will minimize that impact."

USDA explains that they will not be releasing any information (cattle age, testing location or type of animal) unless the animal is a confirmed case of BSE. After the first screening test comes up as inconclusive, USDA says it conducts another screening test in addition to the IHC test. Feedstuffs Sally Schuff asked Clifford if a second rapid test has been conducted and what the results were for the animal found to be inconclusive on Tuesday, June 29. Clifford replied that only confirmatory results will be released, not secondary screening tests. Those results are not expected until next week sometime.

Cattle Buyers Weekly reported that the second inconclusive BSE involved an 8-year-old cow, probably a dairy cow. "The age of the cow in the second case raises additional concerns that this animal may be more likely to test positive eventually because of its age, say observers," the article says. USDA did not confirm this information on a conference call it hosted on Wednesday afternoon.

USDA officials have been unwilling to give a statistical number for the number of expected false positives that rapid tests may reveal. Earlier this week USDA Undersecretary for Regulatory Affairs J.B. Penn says one inconclusive can be expected for every 10,000 tested. To date the USDA has tested 8,587 animals with two inconclusives found. Clifford says that the 1:10,000 ratio is referring to Japanese test results. "The Japanese are testing a different class of animals that we are testing. We could see varying results than what they're seeing," he says.

National Cattlemen's Beef Association President Jan Lyons released a statement after the announcement reminding producers that a rapid screening test is used as the first step in a two-part testing process. "USDA expected some inconclusive results from this initial step. Because the rapid tests are sensitive, they are subject to occasional inconclusive results that later prove to be negative," she says. "It is a little like going through the airport metal detector. We all have had the detector beep on us at least once, but it didn't mean we were carrying a prohibited item. It simply meant more testing was needed."

Currently only one rapid test, Bio-Rad Laboraties', has been approved for actual use in the United States. Four others have been approved but haven't had field tests conducted.