Science: Still searching for real facts

The Prime Minister has chosen an odd rallying cry on which to start a war of European non-co-operation: "Beef is safe - the scientists tell us so." To which one is tempted to reply, with Star Trek's relentlessly logical Mr Spock, "Safe, but not as we know it."

The Government line that beef is "absolutely safe" faded away on 20 March, when Stephen Dorrell told the House of Commons that the best explanation to date for 10 recent, unusual cases of Creutzfeldt-Jakob disease (CJD) in young Britons was exposure to BSE before 1989. Since that day, no better hypothesis has emerged. Nor has any new hard evidence. Meanwhile, the scientists have been pushed to the back of the room while the politicians wrangle.

BSE and CJD are strange diseases in that the infective agent is not a bacterium or virus, but apparently a misshapen version of a protein, made naturally by the body, that accumulates and kills nerve cells. Nobody knows exactly what concentration of the infective agent (normally called a "prion") is present in different parts of the cow - such as the meat - before the disease shows up. Experiments with mice indicate that infected cows' brains are infectious (the mice catch BSE) but infected cows' beef isn't. That's not the same as saying beef isn't infectious to humans. And nobody knows if BSE can cause CJD. The science isn't there yet.

Thus it's true - but enormously disingenuous - for the Government to insist that beef poses no risk, and that no link has been proved between CJD and BSE. And it certainly doesn't follow that the beef ban should be lifted. Ten CJD deaths do not make an epidemiological study, but they provide the raw material to give a lot of scientists in the field the shivers.

Unfortunately, there are few reliable sources available for those who want to know what is known and what is only alleged. So how does one get a balanced view? Two new books are already at the booksellers: BSE: The Facts by Brian J Ford, chairman of the history of biology sector of the Institute of Biology, and Lethal Legacy by Dr Stephen Dealler, a medic who has been a consistent independent critic of the Government's approach to the disease in cattle.

Ford's is a thorough book, with details about animal husbandry, proportions of herds and breeds affected by BSE, feed manufacture, and not least the diseases themselves, which are perhaps the most peculiar known to science. Certainly, the book lives up to its subtitle; I did not spot any significant errors of fact.

However, there's a big difference between buying wool and knitting a jumper. Some of Ford's assertions are wrong (such as that the disease which killed the 10 people was kuru, a CJD-like disease that affected cannibals in New Guinea; in fact their symptoms and pathology are quite different) and some of his statistical generalisations are wildly wrong (such as that half of Britain's abattoirs are breaking BSE regulations: in fact, half in a survey were breaking them, so the true figure could be the same, or more, or less).

But Ford provides a useful primer for reading Dealler's book, which moves the whole argument forward and contains a lot of data that the Ministry of Agriculture, Fisheries and Food (Maff) should long ago have released for public consumption - such as how long the epidemic of BSE can reasonably be expected to continue. Dealler's answer, based on some densely-argued statistics, is that in 1999 there will still be between 900 and 8,700 recorded cases. (His figures accord with an independent study published recently by a team at Oxford University.)

Dealler points out that we must have eaten hundreds of thousands of infected cows in the past 15 years which were not yet showing symptoms. Whether the disease is caused by chance exposure to a single dose, or by a build-up of small doses, we should be worried about how much of the prion agent we are absorbing. Dealler takes the conservative, "cumulative" approach and builds it into a big table showing infectivity and dosage.

He interprets this to show that for adult Britons, there's no benefit in stopping eating beef: the biggest risk (in terms of exposure to the BSE prion) has already been taken. Stopping now might halve your risk, but to improve your chances (assuming that BSE can cause CJD), you need to cut that risk tenfold - which isn't possible now. You can't un-eat past meals.

But a parallel conclusion he draws is that foreign visitors and children would be better off not eating British beef, "just as you advise people not to drink the water when they visit some foreign countries". How strange if the highly developed nature of our farming has brought us to the same stage as a developing country. Not that Mr Major will be too worried. Politics, not science, is in the driving seat, reading off a faulty map.

CHARLES ARTHUR

'BSE: The Facts' by Brian J Ford (Corgi Books, pounds 4.99). 'Lethal Legacy: BSE - The Search for the Truth' by Dr Stephen Dealler (Bloomsbury, pounds 5.99).