'It is the nature of an hypothesis, when once a man has conceived it, that it assimilates everything to itself as proper nourishment; and, from the first moment of your begetting it, it generally grows the stronger by everything you see, hear, read or understand. This is of great use!' (Laurence Sterne, Tristram Shandy, 1767)
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When Laurence Sterne wrote these words he was suffering from pulmonary tuberculosis. At that time the contemporary hypothesis was that this disease was attributable to damp living conditions. It was not until 1882 that Robert Koch demonstrated the true cause of tuberculosis - so Sterne himself fell victim to an incorrect hypothesis.
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In the early 1960s it was suggested that scrapie played a part in the causation of multiple sclerosis - a hypothesis that is now firmly rejected. But at the time the hypothesis was treated with caution, noted, investigated further and finally rejected.
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Every year hundreds of new or 'new variant' diseases are described in medical literature. For every disease of unknown causation, causes and (especially in former times) cures have been promoted and marketed. And scientists have always fought for their own theories of causation and cure.
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But, in the past decade, another trend has emerged - the demand by the public to be protected from risk. This trend has usually assumed that professionals know the risk, know the cause, and could protect the public, but fail to do so for political or material reasons.
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There are many dreadful neurological diseases of unknown causation and for which there is no known cure. Many are relatively common. Multiple sclerosis (MS), motor neurone disease and Alzheimer's disease represent a personal tragedy to patient and family and constitute a major public health and medical services problem. Some diseases are able to capture the public imagination for the horror of their manifestations.
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Creutzfeldt-Jacob disease is one of the rarest neurological diseases, especially in its new variant form; but it is a disease that has captured popular imagination probably more than any other. The reason? The link with BSE. This link was suggested without any supporting evidence in the discussion following the first description of the new disease, 'new variant CJD' (nvCJD), in 1996. Since then, studies in transgenic mice have produced suggestive evidence that a link exists. But much doubt remains.
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The explosion of BSE in the UK during the 1980s has not been followed (at least not yet) by a parallel explosion of cases of nvCJD - despite the fact that we are now 15 years on and this interval of time is thought to be a likely interval for the disease to incubate. BSE cannot reliably be transmitted to calves by feeding them infected feed. And in man the tiny number of vCJD cases (about 12 per year) is surprising if most of the population (60 million) were eating infected beef in the early 1980s.
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The only explanation for these observations is if the incubation period for the disease is very long indeed. Or has vCJD a cause entirely separate from BSE?
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The first real clue to this possibility is the clusters of cases that are now emerging in Queniborough and Armthorpe. Here is the opportunity to study, with an open mind, alternative possibilities.
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It is no criticism of SEAC (Spongiform Encephalopathy Advisory Committee) to point out that it is made up of experts in prion diseases. Precisely because of their expertise and interest in this particular field, these may not be the people best equipped to look at other possibilities for the cause. But the UK government has relied exclusively on the advice of this group and we know only too well the heroic measures this advice has led to.
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If in the 1960s the UK health secretary had announced that scrapie was suspected of causing MS, and if in the 1960s the public had learned to demand a 'no risk' environment from its politicians, we would have presumably slaughtered our sheep and destroyed the sheep meat and wool industries.
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The public and politicians will have to relearn that many things are unknown or uncertain, and that it may be wiser to live with a measure of risk until convincing scientific evidence is available.
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Dr Richard Godwin-Austen is consultant neurologist at Papplewick Hall, Nottingham.
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