It is time to call a halt to the series of unprincipled scare stories that are being peddled about BSE and new variant CJD. The latest, which comes directly from the Nobel Prize-winning scientist, Stanley Prusiner, is the most outrageous of them all. Last weekend he gave warning that people who had eaten beef or lamb in Britain were still at risk from vCJD, a disease for which there is no known cure. He called for nationwide tests to determine how many of us had been exposed to the infectious prion proteins he believes to be the cause of the disease. His latest experiments, he said, suggested that the prions might be lurking, not just in the brains and spinal columns of cattle and sheep, but in the muscles as well. “A million cattle infected with BSE entered the British food chain, so almost everyone in the country will have been exposed. . .” he said.

It would be hard to exaggerate the sheer folly and irresponsibility of this comment. If taken seriously, it would cripple the farming industry and demand a massive testing programme, spreading alarm throughout the population. One estimate suggests that for every real case of infection exposed by Prusiner’s testing programme, there would be at least nine “false positives”, that is, people who appear to be incubating the disease but have not in fact contracted it. Their jobs, insurance and life prospects would be blighted. And, since there is no cure, the real victims would gain nothing save the knowledge that they face a painful and lingering death.

So what on earth was the point? It seems to be that Prusiner’s thesis about the link between BSE and vCJD is running out of steam. It is now five years since he won his Nobel Prize for claiming that degenerative diseases such as CJD are caused by prions — cell membrane proteins that are found in high concentration in the brain or spine. With the acceptance of his thesis, the scientific establishment threw its weight behind it. Warnings about a possible vCJD epidemic began to proliferate, with the CJD surveillance unit in Edinburgh regularly adding to the grim scenario. Estimates of a death toll of more than 100,000 in Britain were predicted.

Yet what is the reality? The latest figures from the Edinburgh unit show that there have been 15 cases this year, down from 20 last year, and 28 the year before. That is approximately one in three million. The numbers are, in fact, falling, not rising. Closer scrutiny reveals other curious statistics. An article in The Lancet reported that the geographical distribution of vCJD and BSE did not tally. The highest concentration of BSE-affected cattle was in the South and West of England, while most cases of vCJD were in Scotland. A damning article in the British Medical Journal, written by George Venters, a consultant in public health medicine at the Lothian Health Board, argued that the disease was neither new nor caused by prions. Headlined “New variant CJD: the epidemic that never was”, it drew a furious response from prion supporters. But nothing has caused Venters to change his mind.

There is, of course, money to be lost and reputations to be damaged if the bottom drops out of the prion creed. Now, however, the whole issue is about to become political. Later this month Margaret Beckett, the Environment Secretary, will be asked to approve a new research grant for Professor Alan Ebringer of King’s College London, a distinguished scientist who has identified a microbe which he believes was responsible for BSE and which may also hold the clue to multiple sclerosis. His thesis is radical, like all the best scientific advances, but at least it is statistically consistent. So far it has been opposed by Seac, the government committee which approves research projects. That is hardly surprising: six out of the 12 Seac members are involved in prion research.

The time has come, therefore, to explore the alternatives. Mrs Beckett should have the courage to challenge the Prusiner orthodoxy and break new ground. Anything must be better, surely, than what Venters calls “terrifying a population to keep interest going in a rare disease”.