Research finds the matter, which causes chronic wasting disease, in muscle. It had been thought to be only in nervous-system tissue.
By Katy Human
Denver Post Staff Writer
A person who eats venison could swallow the proteins shown to cause a deadly brain disease in deer, elk and moose, researchers reported today.
Their article in the journal Science represents the first time scientists have found the proteins that cause the affliction, chronic wasting disease, in the meat and muscle of deer.
Previously, it had been found only in the brain, spinal and lymph tissues. Health officials have long reassured hunters they would not be exposed to the disease as long as they did not touch or eat those parts.
A Colorado expert on the disease said the discovery doesn't necessarily mean that Colorado hunters should change their practices or that venison eaters should change their habits.
There's still no evidence that a person has caught a brain disease by eating a sick deer, said the expert, Mike Miller, a veterinarian with the Colorado Division of Wildlife.
In the Science article, Colorado and Kentucky scientists said they had found "significant" amounts of disease-causing prion proteins in the hamstring muscle of deer dying from chronic wasting disease.
When injected into laboratory mouse brains, the muscle tissue caused wasting disease.
"People who are handling or consuming deer meat are going to be at risk to consuming prions," said Glenn Telling, a molecular biologist at the University of Kentucky and co-author of the study.
Scientists still don't know whether the deer prions can sicken people, Telling said, but the finding "raises the stakes."
Prions that cause a similar disease - mad cow - have never been found in cow muscle tissue.
Even so, a few people who ate mad-cow-infected beef have caught and died of a deadly brain disease, called variant Creutzfeldt-Jacob.
"People are more likely to run a risk of exposure to chronic wasting disease proteins" through deer meat than they are to ingest mad-cow proteins by eating beef, Telling said.
"It's clearly there in the meat, but in very small quantities," said Miller, also a co-author of the new paper.
"We've been saying for 10, 11 years now, 'Don't consume deer or elk that appear to be sick,"' Miller said. "If anything, this confirms that our standing recommendations are appropriate."
John Pape, an epidemiologist with the state health department, agreed.
He just submitted a paper showing that the incidence of Creutzfeldt-Jacob disease in Colorado is no higher than it is elsewhere, even in places without chronic wasting disease.
"We can't exclude that possibility, that a rare (human) case could occur, but it's certainly not occurring at a high rate," Pape said.
The new study suggests that experts can monitor the incidence of chronic wasting disease by taking muscle samples from wild animals, Telling said.
Previously, the only reliable tests for the disease involved killing deer, elk or moose to test brain, lymph or spinal tissue.