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Diagnostic tests for prion diseases need a “quantum leap” in sensitivity if they are to help prevent future outbreaks, says a report from the US National Academy of Sciences.

Basic research into the nature of prions, which cause illnesses such as bovine spongiform encephalopathy (or mad cow disease), will be essential to achieve this, says the report. It was commissioned by the Department of Defense and prepared by a panel chaired by Richard Johnson, professor of neurology at Johns Hopkins University School of Medicine in Baltimore, Maryland.

“We need a fundamentally different approach,” says Johnson. “Incremental improvements in existing tests are not going to do it.” Prion diseases, or transmissible spongiform encephalopathies (TSEs), can only be confirmed after death and even then can be missed. A test is needed that can spot the smallest amount of infectious prion protein that can cause disease, the report says. This would require a sensitivity at least 1,000 times greater than that of current tests.

One possible approach would be to work out the three-dimensional structure of the prion protein, so that a compound could be designed to target it. This has been complicated by the insolubility of prion proteins.

Fred Cohen, a prion researcher at the University of California, San Francisco, welcomes the report. “It was a good group of people to probe these questions,” he says. Although there has been an epidemic of TSE among elk and deer in the Midwest, there is no mad cow disease in the United States, and Cohen doubts whether the political will exists to fund the work.

Congress handed a major role in prion research to the defence department last year, when it authorized the National Prion Research Program. This distributed US$42 million in research grants in 2002 and may win further funds in 2004. Part of the military's interest concerns its troops abroad, who may have been exposed to mad cow disease. Prion diseases are also a potential bioterror agent.

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