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Mad cow controversy continues

Several years ago, as media-driven paranoia over mad cow disease in the United Kingdom reached its peak, British Health Consultant George Venters asked a question, the same question Americans are asking today: Can eating beef cause people to develop the human equivalent of mad cow disease? The answer he formulated after extensive investigation ignited a firestorm of debate that is still raging.

The prevailing view — one that Venters challenges — is that a mysterious proteinlike particle, known as a prion, found in the brains of cattle infected with mad cow disease, somehow crossed over into humans, causing a new variant form of Creutzfeldt-Jakob disease, commonly known as nvCJD.

Creutzfeldt-Jakob disease is a devastating condition by any measure, one that destroys the human brain in much the same way mad cow disease affects bovine brains. This much is true. And, yes, what has been perceived as a new form of CJD, detected in relatively larger numbers of people at about the same time as the mad cow media frenzy in Britain, bears an especially eerie resemblance to the bovine disease.

This has naturally led many scientists to speculate that eating beef from infected animals somehow is related to CJD in humans. But what began as speculation never has been proven conclusively — precisely the point Venters is trying to make.

First, as Venters argues, a very robust species barrier exists between humans and other mammals — a fact that has been borne out in studies with laboratory mice. Mice that were genetically altered to carry the human prion associated with nvCJD have not contracted BSE, even after they were injected with the prion associated with the cattle disease.

Venters even questions whether the so-called new variant CJD associated with mad cow disease really is new and variant. Granted, new CJD cases involving mostly young people occurred at about the same time in Britain that BSE was diagnosed in cattle. This led many scientists to speculate there was a link between the two. Until then, CJD cases typically were associated with much older people. Even so, one of these young victims was a vegetarian, and the percentage of victims who had eaten hamburger was, statistically speaking, no different than the general population.

Venters uncovered even more tantalizing clues in the course of his investigation. As he learned, the first recorded case of CJD in the 1920s — long before BSE was detected in Britain — involved a 23-year-old patient whose clinical symptoms were entirely consistent with those of younger CJD patients in Britain in the 1990s.

These findings and many more led Venters to conclude that nvCJD was not new and variant after all — a rare disease, yes, but one that has simply not been adequately diagnosed.

Venters' main argument has been supported by Britain's Edinburgh-based National CJD Surveillance Unit. The scientific panel associated with this unit concluded that there was little evidence to establish a positive link between eating beef and nvCJD, though they were not willing to exclude such a link. They were, however, unable to identify other dietary or occupational factors that may contribute to the disease.

Media hype notwithstanding, CJD remains a mystery disease with no known cause. And it may be years or even decades before the actual cause is known.

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