Brain & Nervous System Health Center

Of Mad Cows, Cannibals, and New Life Forms

From the WebMD Archives

Jan. 25, 2001 -- Mad cow disease, kuru, and Creutzfeldt-Jakob disease are all diseases that make the brain degenerate into a spongy mess; they can be transmitted by contact with infected animal or human tissue. Mad cow disease is believed to be carried in feed made of animal by-products and can infect both the cow and the human who eats the cow's meat.

The scary thing is that the meat you eat from your local supermarket or fast-food chain does not necessarily come from an American cow -- or even from one cow, making it possible that contaminated meat from a foreign country could end up on your grill. Even scarier is the fact that there is no good test to detect the agents -- called prions -- that cause the disease.

It is important to realize that even if the worst predictions come true, the number of people who will actually get the disease is likely to be quite small. This is because of the way in which the disease is transmitted and the preventive efforts of governmental agencies worldwide. So while I am concerned about the safety of our food supply, the story here is the story of the prion.

Please deglaze those eyes, and we can begin.

A mysterious disease in Papua New Guinea was reported around the turn of the 20th century but remained largely uninvestigated until the 1950s. Researchers studying the tribes there found that members of one tribe were dying of an unusual brain illness. Initial reports were that the disease commonly infected women, who initially lost their ability to walk and use their hands in a coordinated fashion. Later, they couldn't walk at all, started to lose their speech, had outbursts of laughter, and lost control over their emotions. Patients eventually lost all control over their muscles and died as a matter of course.

People from neighboring tribes, who lived in the same area and came into regular contact with members of the affected tribe, did not get the disease. The scientists looked at differences between the tribes and discovered one big one.

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The affected individuals were cannibals. Women in this tribe were the main participants in removing the victims' arms and legs, stripping the muscle, removing the ... well, you get the picture. Either they were ingesting a toxin, which seemed unlikely since the -- there is no delicate way to say this -- people being eaten did not suffer from the malady, or they were ingesting some kind of infectious agent that was inactive in the host.

So the search was on to find the host. For nearly 30 years, scientists tried identifying the infectious agent and failed, despite using every technique successful in identifying bacteria, viruses, yeast, and other infectious agents. They did finally succeed in identifying something that was infectious, but they couldn't figure out what it was, other than the fact that it seemed to have protein in it.

This is where things get really interesting. Every living thing has DNA and RNA. Even viruses, the smallest known living things, have at least one of the two, since these acids form the genes that are essential to creating and fostering life on this planet. Scientists fried the infectious agent using ultraviolet rays and ionizing radiation -- in effect destroying the DNA and RNA. The infectious agent survived.

Imagine an astronomer willing to consider that the Earth has two moons. It was about as heretical for a biologist to consider that there may be a life form with no genes. But that was what the evidence indicated, and so, in the best traditions of science, researchers slogged away for a further 15 years and finally identified the infectious agent -- a protein, nothing more or less. Scientists subjected this protein to several more years of the third degree using enzymes, heat, and all the other techniques that protein detectives use to interrogate their suspects.

Today, nearly a hundred years after the initial reports, we know what this protein, called a prion, looks like. We also know that it may replicate like a virus by borrowing the equipment it needs from the host. We do not know if this can be called a new life form or not -- that may end up being a debate between scientists and philosophers.

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Whether or not we can find a cure for this cause of "mad cow disease" is, however, not a matter for debate. We will, eventually -- just look at the people going after it.

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