Infected animals waste away, becoming emaciated and listless. "A (sick deer) might have its head down, its ears flattened, instead of up and alert," says Beth Williams, a veterinary pathologist at the University of Wyoming Department of Veterinary Sciences in Laramie. "It would have a spacy look in its eyes. It would be able to see you, but wouldn't care very much."
Once symptoms emerge, death comes within weeks as the disease destroys the animal's coordination, leaving it unable to stand.
"Often the actual cause of death turns out to be pneumonia," says Williams. "I wouldn't be surprised if many are finished off by coyotes."
Monitoring programs carried out over the past four years in Colorado and Wyoming suggest that the disease infects 5 percent of the deer and approximately 1 percent of the elk in northeastern Colorado and southeastern Wyoming.
Wildlife officials from both states believe the disease is confined to this relatively small area. South Dakota has recently identified a dozen cases in captive elk, further complicating the picture.
While chronic wasting disease is no newcomer to the Rockies, the rate of infection, particularly for deer, seems to be excessively high. Five percent is "a staggering figure," says Clarence Gibbs, head of Transmissible Spongiform Encephalopathies (TSE) research at the National Institutes for Health, in Bethesda, Md. "That should be sufficient stimulus for people to get off their suitcases and try to figure out where it's coming from."
Chronic wasting disease (CWD) was first detected 31 years ago in captive mule deer near Fort Collins. The disease is one member of a family of rare and mysterious brain illnesses called TSEs that kill by eating microscopic holes in the brains of their victims. Mad-cow disease is another form of the illness, as is Creutzfeldt-Jakob disease in humans, and scrapie, which has been endemic at low levels in American sheep since the 1940s.
Research is stepping up. Colorado is expanding its monitoring program for the next hunting season, while South Dakota plans to initiate a surveillance program for wild deer and elk herds. Last October, the U.S. Animal and Plant Health Inspection Service initiated a modest seven-state program to determine if the disease is present outside of Colorado, Wyoming and South Dakota.
Currently, little is known about how chronic wasting disease is spread among deer and elk, let alone whether other species can be infected. Experiments are under way at the Animal Research Service's laboratories in Ames, Iowa, to test cattle susceptibility to the disease. Results are at least 18 months away, says Randall Cutlip with the Animal Research Service.
There are inevitable concerns about whether the infection can pass from game to hunters, especially since mad-cow disease made the jump from beef to people.
Public health officials don't believe that humans can contract the disease by eating infected animals, though they acknowledge the possibility exists.
"Is chronic wasting disease transmissible (to humans under normal conditions)? The answer is nobody knows," says John Pape, an epidemiologist with the Colorado Department of Health, "The evidence suggests it is not."
Colorado officials are asking hunters handling deer and elk from affected areas to use precautions, including wearing gloves when dressing out animals, avoiding the most infectious tissues, the brain, lymph and spinal tissue, and boning out the carcass.
Wyoming has yet to issue health recommendations for deer and elk hunters, but "the risk is so small, I wouldn't worry about it at all," says Tom Thorne of Wyoming Game and Fish, who adds that he regularly hunts and eats deer from southeastern Wyoming.
What does worry Thorne is a possible spread of the disease to uninfected deer and elk herds. "If, in the worst-case scenario, this disease spread from deer to deer ... across the country, it could play a role in limiting your (deer) population," he says.
The spread of the disease among captive animals may represent a more immediate threat.
"This is probably going to cause quite a bit of problem in the game-farm industry," says Wyoming's Tom Thorne. Captive herds seem to facilitate the spread of chronic wasting disease, just as they do other communicable diseases like tuberculosis. Already, several cases have been linked to game farms. The captive South Dakota elk that developed the disease came from a source herd that included animals from the Colorado-Wyoming infection zone as well as from Canada, according to Sam Holland, South Dakota's state veterninarian. Additionally, two recent Canadian casualties, a deer and an elk, both originated from U.S. game farms.
All of which means that either chronic wasting disease is already more widespread than suspected, says Thomas Pringle, a molecular biologist and public lands advocate, or game farms are allowing it to spread beyond the Colorado-Wyoming focus area. "That's how scrapie got spread around," says Pringle, who operates the Mad Cow Disease home page for the Sperling Foundation. "They brought in (infected) Suffolk sheep from England (in the 1940s). They were buying and selling them all over, then pretty soon you have it in 39 states."
Chris Carrel freelances from Federal Way, Wash.
You can ...
* Contact the Colorado Division of Wildlife at 303/297-1192;
* Contact Tom Thorne at the Wyoming Department of Game and Fish at 307/777-4586;
* Contact Beth Williams, University of Wyoming Department of Veterinary Sciences, at 307/742-6638.
* Find a comprehensive source of news articles and scientific articles about TSEs on the Mad Cow Disease home page at http://mad-cow.org.
* Read two recent books, which provide excellent background information on TSE disease: Deadly Feasts by Richard Rhodes (HarperCollins, 1997), and Mad Cow, USA: Could the Nightmare Happen Here? by John Stauber and Sheldon Rampton (Common Courage Press, 1997).