ecoglobe [yinyang] news (31 October 1999)

ecoNews list | previous | next | ecoglobe front page | site index & keywords
"prions" (proteinaceous infectious particles)

Mad Deer Disease: Can Venison Kill You? by Frank Miniter

A fatal brain disease is spreading in deer and elk... and hunters are dying from a very similar illness.

The disease that struck the three hunters is ominously similar to another disease that's spreading in deer and elk in Colorado and Wyoming. This possible connection has some people pointing to deer meat and crying killer.

The accusation could prove true. The disease found in deer and elk is called Chronic Wasting Disease (CWD), and it's closely related to Creutzfeldt-Jakob Disease (CJD), which is what killed the hunters. Both CJD and CWD are classified as "transmissible spongiform encephalopathies" (TSE). Diseases don't always make the leap from one species to another, but there is a connection between chronic wasting disease and Creutzfeldt-Jacob that has many scientists concerned: Another TSE-bovine spongiform chronic encephalopathy (BSE)-spread from cattle to humans in the United Kingdom, where it was dubbed "Mad Cow Disease."

Mad Cow Disease exploded in U.K. cattle herds in the late 1980s and early '90s. But it was not until 1996 that it was found to have crossed over to humans. Since then, 43 people are known to have died in the U.K. from Mad Cow Disease, but because of its long incubation period-possibly up to 20 years-it may yet kill many more. The disease resulted in European bans on British beef and forced the destruction of more than half of the cattle in the U.K.

Because of the similarity, CWD has already been nicknamed "Mad Deer Disease," but it hasn't yet proved as sinister. In fact, another TSE called "scrapie" has afflicted sheep for at least 250 years and has never been found to cross over to humans. Still, because of Mad Cow Disease, CWD is hitting the hunting world like a horror movie monster, lurking unseen in the shadows.

Scientists, however, are on the monster's trail. More than a dozen states and the federal Centers for Disease Control (CDC) in cooperation with the Animal Plant Health Inspection Service (APHIS) are pouring money and resources into a thus-far-quiet, but nevertheless massive, investigation. They're trying to answer two questions: Is CWD killing people? And where is CWD?

To answer the first question, the CDC is taking a street cop approach by chasing down every lead that comes into its Atlanta headquarters. And with what they've found so far, this horror movie is starting to feel more like an X-File. Larry Schonberger, a medical epidemiologist for the CDC, says, "I've sent one of our epidemiologists out to investigate to see if there's a link between CWD and the [three] hunters' deaths. I did this because two of the victims were young [one was 27 years old, the other 30]. That's very unusual. CJD normally shows up in people well over 30. But our scientist's initial report is that the deer eaten by the victims had not come from [known] infected areas. But we're taking no chances. In fact, a young girl died in a southern state from CJD who had reportedly eaten venison that her father had shot in Maine, so this year 300 deer will be checked for the disease in Maine.

"At this point we can't rule out a link between Chronic Wasting Disease and the hunters' deaths, but I think it's unlikely. CJD occurs all over the world at a ratio of about one in 1 million people. Each year in the U.S. 250 to 300 people die from CJD. So it's understandable that a few of the victims happened to have eaten venison," says Schonberger.

Meanwhile, APHIS and many state agencies are doing a broader search to discover if CWD can be found outside known infected areas, and to find out how fast it's spreading from the infected area. Since there is no accurate test that can be performed on living animals, scientists are checking brain samples. The samples are collected at deer check stations and meat processors. From there they are sent to a number of labs for analysis. Colorado and Wyoming each check thousands of samples annually at their own research facilities, but other states, such as Nebraska, South Dakota, Montana and Nevada, send their samples to the APHIS lab in Ames, Iowa. So far no wild deer or elk outside of Wyoming and Colorado have shown up with the disease. CWD has been found in elk produced in the game-farm industry, however.

Both CDC and APHIS efforts are designed simply to get a fix on the situation. Right now not much can be done to stop or prevent Mad Deer Disease because scientists know so little about it. To get answers, however, labs worldwide are intensively studying all spongiform encephalopathies. The CDC, for instance, is investigating this group of pathogens at its Prion Disease Pathology Surveillance Center at Case Western Reserve University in Cleveland. But despite the intensive research efforts, answers are slow to come.

In fact, scientists don't even agree on what causes TSEs, although there is wide support for a theory put forth by Stanley Prusiner, M.D., a professor of neurology at the University of California at San Francisco, whose research won him the Nobel Prize in Medicine in 1997. Prusiner theorizes that "prions" (proteinaceous infectious particles) cause this family of diseases, and not a virus, as was previously assumed. His chief reason for fingering "rogue proteins" is that the chemical and physical procedures that destroy most viruses don't affect TSEs, whereas procedures that have been found to degrade proteins seem to inactivate them. Prusiner's hypothesis is that prions kill by turning normal proteins in nerve cells into infectious ones by forcing them to alter their shape.

A Doomsday for Deer?

In light of the recent conjecture about CWD killing humans, it's easy to overlook one certainty about this disease: It kills deer. The ramifications of that indisputable fact are almost as unsettling. Before we go on, keep three things in mind: CWD is spreading, CWD is always fatal and CWD has no known cure.

In the infected areas of Wyoming and Colorado, about 4 to 8 percent of deer and 1 percent of elk have the disease, according to Beth Williams, a professor of veterinary services with the University of Wyoming, and Mike Miller, a biologist with the Colorado Division of Wildlife.

"It's been spreading slowly since it was first found in the wild in 1981," Williams says. "We think [CWD] passes from animal to animal through bodily fluids. So it probably takes physical contact of some kind to pass the disease."

That said, the spread of CWD may soon pick up speed because whitetails may be next on its hit list. Thus far the disease has mostly spread in mule deer up the South Platte drainage in northeastern Colorado. Mule deer have fairly thin population densities along the river, but whitetails have heavy population densities in this area. This dilemma has Miller worried because the whitetail's heavier population density means there is a greater chance of physical contact, which means CWD could move more rapidly. "Based on some computer models that we did at the Division of Wildlife, this scenario could prove devastating," Miller says.

"The only preventive measure we can take is to cut down the deer population in the infected areas. But these areas are popular with hunters, so that would be controversial. As a result, right now we're just checking for the disease, but unless something is done, CWD could spread farther and farther east. I'm not saying that it'll be in New Jersey next year, but in 10 or 15 years, who knows?"

So this article ends not with a climax, but with a "to be continued." Many questions still surround what we hope is erroneously named Mad Deer Disease. Consequently, we're left in the dark, speculating as to what it means to deer, to hunting and to hunters.

[This is from "Outdoor Life on line" at:]

** NOTICE: In accordance with Title 17 U.S.C. Section 107, this material is distributed for research and educational purposes only. **
Feedback to: <>






ecoNews list | previous | next | top | ecoglobe front page | site index & keywords

ecoglobe [yinyang] news (31 October 1999)

this site: