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Professor skeptical of link between BSE and vCJD

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Kathy

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AUBURN, Jan. 6, 2004 --- The image of one’s brain turning into sponge after eating meat from a diseased cow is enough to leave anyone weak in the knees. But could it be that this image is nothing more than that – a horrific image with little basis in fact, conjured up largely through media hype?

Some scientists think so, including Dr. Jean Weese, an Alabama Cooperative Extension System food safety expert and Auburn University associate professor of nutrition and food science.

The prevailing view is that a mysterious proteinlike particle, known as a prion, found in the brains of cattle infected with bovine spongiform encephalopathy, commonly known as mad cow disease, is linked with what some scientists believe is a new variant form of Creutzfeldt-Jakob disease in humans. Supporters of this view believe that people who have developed this variant form of CJD ate beef from animals infected with BSE.

Creutzfeldt-Jakob disease is a devastating condition that destroys the human brain in much the same way BSE affects bovine brains. All forms of CJD are similar to BSE in cattle. But what is perceived to be the newer form of CJD, typically known as nvCJD for new variant Creutzfeldt-Jakob disease, was not detected until the 1990s, at about the same time cattle in Britain tested positive for BSE. This led some scientists to conjecture that eating beef from animals with BSE could result in an increased risk of developing nvCJD.

But what began as speculation has never been proven conclusively, Weese said.

“With the evidence we have now, I’m not willing to say that eating beef from cattle infected with BSE causes a variant form of Creutzfeldt-Jakob disease in humans,” she said. “In fact, there is no conclusive evidence that CJD is caused from eating beef of any kind.”

Weese reached this conclusion through reading of existing research, especially that of George Venters, a British public health consultant, who conducted his own investigation into the alleged link between BSE and the variant form of CJD in humans. His findings, which were highlighted in a 2001 edition of the British Medical Journal, sparked an international debate.

“First of all, as Venters points out, there is a very robust species barrier between humans and other species,” Weese said.

“This has been borne out in research with laboratory mice. Mice that were genetically altered to carry the human prion protein associated with CJD 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 linked with mad cow disease really is that new and variant.

“Several seemingly new CJD cases involving mostly young people occurred at about the same time in Britain that BSE was diagnosed in cattle, leading many scientists to speculate that there was a link between the two.

“Curiously, one of these victims was a vegetarian, and the percentage of victims who had eaten hamburger was, statistically speaking, no different from the general population,” Weese said.

This led Venters to ask not only whether there was actual evidence of a new form of CJD but whether there was any link with eating beef.

As Venters soon discovered, the first recorded case of CJD in the 1920s --- long before BSE was even known to exist in cattle --- involved a 23-year-old patient whose clinical symptoms were entirely consistent with those of the younger CJD patients in Britain in the 1990s.

“The finding lends credence to Venters’ argument that nvCJD is a rare disease that has been around for a very long time but that has not been adequately diagnosed,” Weese said.

In 2001, scientists with Britain’s National CJD Surveillance Unit in Edinburgh added further support to Venters’ findings. They stated 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. The scientists, however, were unable to uncover other dietary or occupational factors that may contribute to the disease.

Weese believes Venters’ findings, coupled with those of the CJD Surveillance Unit, underscore the fact that CJD remains a mystery disease with no known cause.

“How do these prions appear in the brains of otherwise healthy people, resulting in CJD? We don’t know. And it may be years and even decades before we know why.

“But one thing is for sure, the mystery that shrouds this disease and the fear it causes among the general public is precisely why it is so prone to the kind of media hype we’ve seen within the last few years.”

[Source: Dr. Jean Weese, Alabama Cooperative Extension System Food Scientist and Auburn University Associate Professor of Nutrition and Food Science, (334) 844-3269; Writer: Jim Langcuster, Extension Communications Specialist, News and Public Affairs, (334) 844-5686.]
 
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