Researchers Wary of Mad Cow-like Disease in Wildlife

January 24, 1998 Web posted at: 11:52 a.m. EST (1652 GMT)

ESTES PARK, Colorado (AP) -- The emaciated mule deer stares blankly into space. Then, stumbling in small circles, it falls over dead, another victim of chronic wasting disease.

It is a grim sight for wildlife officials working in the Rocky Mountains on the border of Colorado and Wyoming, one of only two spots in the world where the disease has appeared.

For health officials, a frightening question must be answered: Will this terrible illness cross over to the human population?

The National Institutes of Health is investigating because mad cow disease, similar to the chronic wasting disease that has struck mule deer and elk, has been linked to a brain-wasting malady in humans -- Creutzfeldt-Jakob disease -- that has killed 20 people in Europe.

"We know there's a link between the diseases, not a causal link necessarily, but they're the same kind of disease," said Byron Caughey, biochemist at the NIH's Rocky Mountain Laboratories in Hamilton, Montana.

"Of great interest is whether we have to worry about it being transmitted into other animal hosts, whether cattle or humans," he said.

About 6 percent of mule deer in the area of northern Colorado and southern Wyoming suffer from chronic wasting disease, or CWD, said Todd Malmsbury, spokesman for the Colorado Division of Wildlife in Denver.

There are an estimated 550,000 mule deer -- a brown, white-tailed species with big ears -- in all of Colorado.

Like mad cow disease, or bovine spongiform encephalopathy, and the new strain considered its human equivalent, Creutzfeldt-Jakob disease, CWD destroys brain tissue and kills its victims.

Both Creutzfeldt-Jakob and CWD leave spongelike holes in victims' brains.

Creutzfeldt-Jakob may lie dormant for years, but once symptoms appear -- loss of muscle control and dementia -- it quickly destroys the brain.

It is rare, afflicting just one in a million people annually in the United States. But it's fatal, killing about seven months after symptoms appear.

All three diseases -- mad cow, Creutzfeldt-Jakob and the wasting disease -- are blamed on infectious rogue proteins called prions, which are mutant versions of proteins that occur normally in the body.

An American biochemist, Stanley Prusiner, won the Nobel Prize in medicine in October for discovering the Jekyll-and-Hyde protein that causes these brain-destroying illnesses. Prions are considered an entirely new type of disease-causing agent, distinct from bacteria, viruses, fungi or parasites.

No one has become sick from carrying the wasting disease -- but wildlife officials require hunters to turn in the heads of deer or elk they've killed. If the brains test positive, the hunters are advised to dump the meat.

Forty deer turned in during the past hunting season tested positive, Malmsbury said.

While the NIH is interested in whether the wasting disease can jump to humans, federal and state agencies have launched three studies to determine its transmissibility to cattle, said Mike Miller, a state wildlife veterinarian.

In Iowa, researchers are injecting brain material of infected wildlife into the brains of cattle. At the University of Wyoming, infected brain material is being given to cattle orally.

In addition, researchers are investigating whether the disease can be spread through contact, letting cattle live with deer herds that have contained infected animals.