WASHINGTON (Reuters) -- The muscles of deer affected by a mad cow-like disease carry the infectious prions that spread the illness, meaning that venison could potentially spread the agent to humans, researchers reported.

They said leg muscle tissue taken from mule deer with chronic wasting disease (CWD) infected specially bred mice when they were injected with the tissue.

While stressing that was a long way from showing venison was infectious, researcher Glenn Telling of the University of Kentucky said the study showed it could be.

Chronic wasting disease is a transmissible spongiform encephalopathy (TSE), one of a family of diseases that includes scrapie in sheep, bovine spongiform encephalopathy (BSE), or mad cow disease, in cattle and Creutzfeldt-Jakob disease (CJD) in people.

Like scrapie, BSE and the other diseases, it gradually destroys the brain and it is always fatal. It is caused by misshapen nervous system proteins called prions.

There is no evidence people can catch CWD. But after BSE swept British cattle herds in the 1980s, people began coming down with an odd version of CJD called vCJD, and it has been linked to eating infected beef.

In Britain, 153 people have died from probably or confirmed vCJD and six suspected vCJD patients are still alive.

Telling and colleagues used a well-established method to test the infectivity of venison, by breeding special mice that are susceptible to CWD, then injecting them with brains and muscle tissue from infected deer.

The mice became ill and the higher the dose, the worse their disease, they report in Friday's issue of the journal Science.

"We don't know if people will develop a human prion disease as a result of exposure to CWD but we know people developed prion disease as result of exposure to BSE," Telling said. "Obviously the most likely route of exposure would be via meat and that is why we addressed this."