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From THE ECONOMIST
August 16-22, 2003
Danger at the Manger
TO A child, mother's little maxim, "you are what you eat", is merely irritating; grow up, however, and it can become quite unsettling. The last decade has seen a spate of food- and farm-related scares, which have undermined confidence in modern agriculture and, in Europe especially, have shaken consumers' faith in the ability of governments to safeguard the food supply and the environment from the depredations of big, bad agribusiness.
A case-in-point is the mysterious mess of mad-cow disease. Britain has seen 180,000 cases of Bovine Spongiform Encephalopathy (BSE) since 1984, but experts reckon that perhaps as many as 1.9m cows were affected between the early 1980s and mid-1990s when the British government finally introduced a full suite of protective measures. The disease has also spread to 22 other countries, with the latest outbreak in Canada earlier this year. The human face of BSE—a terrible neurodegenerative condition called variant Creutzfeldt-Jakob Disease (vCJD)—has already claimed 133 victims in Britain and a handful of others abroad, including the first suspected case in New Zealand earlier this month. Most of the dead are young, but their brains become pocked with holes and scarred by lumps of protein.
Scientists still have more questions than answers about BSE, vCJD and the related scourges which make up the transmissible spongiform encephalopathies (TSEs). Philip Yam's book, "The Pathological Protein", does an admirable job of exploring them. It is generally accepted that BSE arose from trying to boost milk production by feeding cattle the remains of other animals, or meat-and-bone meal as it is more delicately known. But why, when this was a long-standing practice in other countries too, did it appear in Britain first in the 1980s?
One interesting theory, discussed in Mr Yam's book, is that OPEC is indirectly to blame: during the first oil crisis, British renderers started taking short-cuts in preparing meat-and-bone meal in order to cut down on fuel costs; alas, these lost steps may have been critical to deactivating the curious protein particles, or prions, which are thought to be responsible for TSEs. Nor is there complete agreement on how the victims of vCJD came to contract the disease. Is it through eating contaminated beef, with prions passing through the gut? Or some other route of entry? What is the infectious dose? Why have some people contracted the disease, while others, with much the same diet, remained immune? Or will those who now appear resistant simply take longer to develop the disease? Answers to these questions are critical to gauging how far, and for how long, vCJD will spread. One early prediction estimated that 136,000 people would develop the disease in Britain alone; more recent estimates reckon there may be as few as ten deaths in the coming years. As Mr Yam wryly remarks, "Not all the English have gone mad and died, meaning that several other factors must be at play in determining who succumbs to vCJD."
"The Pathological Protein" is full of such sensible observations, a welcome novelty in discussions on this fraught topic. The author is particularly good at explaining the complex and controversial science behind TSEs, as well as the prospects for better diagnosis and treatment—no surprise given his long experience as a writer and editor for Scientific American. But his descriptions of the weird world of prion diseases—whether it is in the Italian family cursed with deadly insomnia or the cooking practices of New Guinean cannibals laid low by kuru, another TSE—are equally graphic.
At the end of the day, no country can consider itself immune to mad-cow disease, and the book has a few suggestions of tougher controls for American regulators to consider. Prion diseases are not just bad luck, concludes Mr Yam, but a warning that "something is out of balance, that the excessive unnaturalness we force on livestock could be catching up with us."
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