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David Smith and David Steffen, veterinary scientists in the university's Institute of Agriculture and Natural Resources, said the larger sampling of animals in the USDA's expanded BSE surveillance testing will result in more inconclusive findings from initial rapid screening. As of Tuesday (June 29) at noon, 8,585 cattle had been screened since June 1.

"Anytime you expand testing, you are bound to have more tests that are inconclusive," Smith said.

On Friday (June 25), USDA announced that an animal produced an inconclusive instead of negative result in initial screening for bovine spongiform encephalopathy, or BSE. Late Tuesday, the USDA announced a second inconclusive result from initial screening. In both instances, further tests are being conducted at USDA's National Veterinary Laboratory in Ames, Iowa, and results are expected soon.

Cattle futures prices fell sharply Monday in response to Friday's announcement, but rebounded somewhat on Tuesday.

Fed cattle prices dropped from $90 to $75 shortly after the nation's only confirmed case of BSE was detected in a dairy cow in Washington in late December, said Darrell Mark, a university livestock marketing specialist. Since then, prices have been rising steadily and are up 20 percent from early year lows.

"Monday's losses appeared somewhat overdone and Tuesday's futures market recovered about half of the losses on Monday," Mark said. He expected that with another inconclusive BSE test being announced on Tuesday night before results of the first case were known, the market will drop sharply today and be quite volatile.

"The industry was expecting approximately one inconclusive test per 10,000 samples, and after one month and slightly less than that number tested, having two inconclusive tests may indicate we'll see more of these than expected," he said. "This will increase market volatility and cause consumers to question the BSE surveillance program." But, the surveillance program is working as it was designed to, he added.

Smith said the public and the markets need to become accustomed to the testing process and the related announcements that will be forthcoming. After the December incident, the USDA was criticized for not disclosing the incident sooner.

"USDA officials now want to be as transparent as possible," Smith said. "So the real issue here is the testing strategy. I won't be surprised if they find additional animals that test inconclusive in initial screening."

Steffen said the initial rapid screening test for BSE, like any test, is never perfect. With this test, scientists typically expect far less than 1 percent of results to be a false positive. The test, an Enzyme-Linked Immunosorbent Assay, or ELISA, uses antibodies to detect the presence of the BSE protein.

If a rapid screening test is inconclusive, additional more specific tests at the National Veterinary Laboratory will confirm the results.

"With the number of cattle being screened, this is something we have to expect," he said. "In a low-incidence population most of the confirmatory test results will be negative."

Smith noted that ELISA is a good test but all tests make mistakes. "If there is a false positive for every thousand tests, then the USDA could expect hundreds of false positive reports from the 200,000 tests to be conducted by next June. The public and the markets need to be prepared for that."

Mark agreed that the public needs to become better informed because "we are going to have a lot of these inconclusive tests. These inconclusive tests do not mean that BSE has been confirmed."

With the resulting drop in cattle futures prices, Mark said some people are asking why the USDA notified the public of the inconclusive results.

"Last time the USDA drew criticism for not announcing sooner," said Mark, who noted that full disclosure will benefit the beef industry if people understand the real issues behind the testing process.

"The press release from USDA about the (June 25) finding was very clear, but right away a few people started talking about it like it was a new confirmed case of BSE," he said.

Mark said that if the tests are confirmed negative, the market will rebound, but a positive finding could hurt domestic demand for beef.

"But there will be a lot of other variables such as the country of origin of the tested animal and whether it was in a beef or dairy herd.

"Last December we dealt with the loss our exports, which account for 10 percent of the market. We have only about one-third of that back so the export market will not have a huge impact this time," Mark said. "What we are watching now is how domestic beef market will respond."

If the USDA continues to post inconclusive results, this could become a common practice that has little effect on the markets, he said. "But this will still cause difficulties if it becomes routine. It's certainly not conducive to strengthening beef demand."

Reproduced courtesy