Published January 01, 2004
Mad cow hysteria is once again frightening beef consumers and hammering the beef industry. It would be easy to blame ignorant media, opportunistic anti-meat activists and cut-throat business rivals for the current mania. But I won’t.
The blame for the groundless alarm rests squarely on the shoulders of scientists who have given way too much aid and comfort to the still unproven notion that mad cow disease poses a risk to human health.
It is widely taken for granted among scientists that mad cow disease (search) is caused by abnormal proteins called prions (search) that somehow build up in the brain and damage it. These same scientists also believe that disease can be spread by consumption of tissue infected with prions.
Humans, so the story goes, allegedly can contract a supposed human-form of mad cow disease, called “new variant Creutzfeldt-Jakob disease” (search) or nvCJD, if they consume prion-containing tissue from an infected cow.
The alleged confirmation of this theory is the 150 or so human deaths attributed to nvCJD in Europe, mostly in the U.K., that have occurred since the mid-1990s following an outbreak of mad cow among British cattle.
Most of the scientists who buy into this theory are also quick to acknowledge that they believe the risk to human health is small but not zero, citing the relatively low number of deaths despite that hundreds of millions of Europeans who consumed millions of pounds of potentially infected British beef since the 1980s.
The prion theory has also been significantly propelled along by the fact that its developer, Dr. Stanley Pruisner (search) of the University of California at San Francisco, won a Nobel Prize for it in 1997.
Despite Pruisner’s Nobel Prize, however, it has not been scientifically established that prions cause any sort of disease ― a fact only reluctantly acknowledged by organizations such as the National Academy of Science’s National Research Council and the National Institutes of Health.
Despite almost 10 years of intense research into the causes and potential ramifications of mad cow disease, the prion theory still does not satisfy the basic scientific test known as Koch’s Postulates (search) for whether a particular microorganism, such as a prion, causes a specific disease, such as mad cow.
Developed by German physician and bacteriologist Robert Koch in 1890, the basic criteria of Koch’s Postulates as applied to the prion theory would be: (1) prions are present in every case of the mad cow disease; (2) prions must be isolated from a diseased cow and grown in pure culture; (3) mad cow disease should be reproduced when the cultured prions are inoculated into a healthy cow; and (4) the prion must be recoverable from the experimentally infected cow.
“The best-kept secret in this field is that [prions] in any form have never shown infectivity,” said the head of Yale University’s surgery department to the United Press International’s Steve Mitchell.
There certainly have been a few exceptions to Koch’ Postulates, but no one has made a case for why prions might be another such exception.
Aside from the propulsion received by virtue of the Nobel Prize, Pruisner’s prion theory seems to have been accepted as the explanation for mad cow simply by default ― that is, no other explanations for mad cow and nvCJD have been developed.
It’s the same sort of shallow thinking that explains why the 150 nvCJD deaths are usually attributed to consumption of infected beef. There is, in fact, no evidence that the 150 victims of nvCJD even ate infected beef, but it is assumed they did because no other explanation has been developed for how they could have contracted nvCJD.
It’s not likely that more affirmative-natured explanations will be forthcoming anytime soon.
As the UPI’s Mitchell pointed out this week, virtually all of the $27 million the National Institutes of Health gave to researchers for work on mad cow-type diseases was directed toward prion theory research.
An NIH spokesmen told Mitchell that the reason for not allocating resources to non-prion research is that few researchers seem to be proposing that type of research.
Other researchers, including an anonymous NIH scientist, told Mitchell that the research community isn’t applying for grants because the agency is biased against non-prion theories and will reject applications for such research.
It could very well be that some virus or bacterium is responsible for the mad cow-type diseases ― but we might not ever know if NIH persists with its tunnel-vision.
The merit of the prion theory seems to rest almost exclusively in the fact that its developer impressed a Nobel Prize committee. It would be much more impressive, however, if the prion theory satisfied Koch’s Postulates.
Steven Milloy is the publisher of JunkScience.com, an adjunct scholar at the Cato Institute and the author of Junk Science Judo: Self-Defense Against Health Scares and Scams (Cato Institute, 2001).