ARLINGTON (AP) - A third case of chronic wasting disease has been confirmed in Carbon County, a sign the wildlife malady may be spreading.

The latest case involved a mule deer shot by a hunter this fall east of Arlington and south of Interstate 80.

About 2,100 of the 2,300 samples submitted by hunters have been tested by the State Veterinary Lab in Laramie and about 100 infected deer have been identified, said Hank Edwards, a Wyoming Game and Fish wildlife disease specialist who tracks chronic wasting disease.

Most of the positive cases have come from deer in eastern and east-central areas of Wyoming where the disease is considered endemic, but the confirmation of three cases in Carbon County in south-central Wyoming may indicate the brain illness is spreading, he said.

The other CWD cases in the county were found last month in deer near Baggott Rocks south of Saratoga and on a ranch near Savery. The Savery case marked the first time the disease had crossed west of the Continental Divide in Wyoming.

The two earlier cases may have been the result of infected herds moving north from Colorado, Edwards said. The Arlington case could have been spread by the Rock River herd, which had one deer test positive last year.

The Game and Fish Department will step up its surveillance, he said.

"That takes a lot of eyes and ears out in the field," he said. "It's not an easy disease to track out in the field."

Chronic wasting disease creates sponge-like holes in the brain, causing the animal to grow thin, act abnormal and die. The disease is similar to mad cow disease.

There is no evidence the illness can be transmitted to livestock or humans, but scientists say they cannot rule out the possibility.

Once found only in small areas of Colorado and Wyoming, chronic wasting disease has spread to elk ranches and wild deer herds as far away as Wisconsin.

It has also been detected in captive or wild animals in Illinois, Kansas, Minnesota, Montana, Nebraska, New Mexico, Oklahoma, South Dakota and the Canadian provinces of Alberta and Saskatchewan.