In a world gripped by fears about the price of food, climate change and the threat of epidemics, we have to trust the scientists. Unless they tell us the truth, what certainties are there? Which is why the story of BSE is such a disturbing one. It's hard to remember now the feeling of national panic created back in 1996, when the first evidence emerged that “mad cow” disease might be transferred to human beings. The fear of a variant form of CJD which could lead to degeneration of the brain as a result of eating infected beef became widespread after the Government admitted that the public had not been told the real facts.

It had apparently concealed evidence suggesting that an infectious agent known as a prion, discovered by the Nobel prize-winning scientist Stanley Prusiner, might be the cause of BSE and, in turn, might pass on a human form of the disease. Professor Prusiner's conclusions were summed up by him in two devastating sentences: “It is thought that BSE is a result of cannibalism in which faulty industrial practices produced prion-contaminated feed for cattle. There is now considerable concern that bovine prions may have been passed to humans, resulting in a new form of CJD.”

That claim led to some frightening headlines, and destroyed the reputation of at least one minister, when John Gummer was photographed feeding his daughter with a beefburger to demonstrate that it was harmless. On the contrary, said the Chief Medical Officer in England, Professor Sir Liam Donaldson, a major epidemic could not be ruled out; he told people to prepare for “thousands” of cases of vCJD. Professor Hugh Pennington, a leading expert in food safety, was quoted as saying: “We are not going to know for several years whether the size of the epidemic will be a small one - in other words in the hundreds - or a very large one in the hundreds of thousands.”

Swayed by warnings like this, Europe swiftly banned all Britain's beef exports, and the Government made it illegal to use animal-based feed for cattle. A programme of slaughtering “at risk” animals was introduced. The theory that BSE could be transmitted in human form still dominates official attitudes to food safety, and remains the accepted view of the scientific establishment. To this day no one openly challenges the prion theory.

Twelve years on, however, that theory and those predictions lie in tatters. The CJD surveillance unit in Edinburgh has recorded only 115 confirmed cases from vCJD in the past 14 years, with none of them establishing a clear connection with eating beef. The total for CJD in general is 1,302, but again there is no proven link with meat consumption. The connection that Professor Prusiner claimed to have demonstrated between cattle fed with animal products and outbreaks of BSE is tenuous at best. And though some scientists claim that the disease is being “carried” by thousands of unsuspecting human beings and could still break out in the future, no one is any longer issuing the old, once-familiar warnings.

Yesterday, as The Times reported on its front page, the chairman of the European Food Services Authority said that the time had come to review the policy that forbids the feeding of cattle with animal products - such as the remains of pigs or poultry. Patrick Wall made the point that it was neither morally nor ethically correct to continue feeding precious grain to animals in the midst of a global food crisis. “Soya meal and other grain prices are going through the roof,” he said. “Is it morally and ethically correct to be destroying this food when people are starving? No one I know is worried about the science. There is only consumer reaction.”

He is right. It is a moral issue. The only reason the ban remains in place is the natural distaste of those who dislike the Prusiner image of “cannibal” cattle. Yet scientists are there to rise above popular prejudice and tell the truth as they see it. Most of those who have studied the disease now accept that the threat of vCJD to people who have eaten infected beef has receded, even if it was ever there. Those honest enough to do so will admit privately that the prion connection remains on the unproven list - the prima facie evidence on which all good research should rest is simply not available. Yet in public they remain silent. And meanwhile we continue feeding cattle with grain that the world's starving now desperately need.

This misleading theory should be publicly challenged. Scientists in the field of neurology or molecular biology cannot continue subscribing to a bankrupt theory when there is no proven evidence to sustain it. They should tell us, and the politicians, that the BSE-vCJD theory cannot in all conscience be sustained any longer, and that the maize being fed to cattle should be used for its original purpose - to feed the starving of the world. Otherwise we will simply have to add them to the growing list of those in authority who no longer command our confidence.

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