LANDER - This fall's alarming case of a diseased moose in western Wyoming remains an "oddball" discovery, a state official said on Monday.

The oddness of the find could be good news - at least in the short term - for elk that congregate on Star Valley feedgrounds near where the moose was euthanized.

The Wyoming Game and Fish Department announced in October that a moose was infected with chronic wasting disease when it was killed just 13 miles from a state-run elk feedground.

Before that discovery, no animal in Wyoming west of the Wind River Mountains had ever tested positive for chronic wasting disease.

A Game and Fish Department scientist acknowledged this fall that the discovery of the disease in far western Wyoming was "alarming."

But Terry Kreeger, veterinary services supervisor for the agency, said on Monday that the disease doesn't appear to be endemic to the area.

Officials have found no evidence the disease is present in other animals in subsequent testing of deer and elk in that region, Kreeger said.

"It kind of lends credence to the theory that this was a migratory moose that came from somewhere else," he said.

One possibility, and perhaps the most likely, is the moose was infected with the disease elsewhere, possibly in Utah, and then wandered into the valley.

Kreeger warned, however, that such a theory is purely speculation at this point.

Regardless, the apparent absence of the disease in other animals is good news for western Wyoming elk, he said.

But he also acknowledged the slow but steady movement of the disease in that direction suggests chronic wasting will probably get to the state's greater Yellowstone elk and deer herds eventually.

Chronic wasting disease has been endemic to southeastern Wyoming for more than 20 years, and it has been moving slowly north and west across the state ever since.

Michael Miller, a veterinarian and researcher with the Colorado Division of Wildlife, describes the disease's movement as something of a "slow-motion epidemic."

The disease is similar to bovine spongiform encephalopathy, or mad cow disease, and appears to be always fatal in deer, elk and moose.

Like mad cow disease, chronic wasting is not caused by a bacteria or virus, but by an altered protein, called a prion, that somehow makes its way to the brain and slowly destroys it by turning normal brain proteins into abnormal ones.

Lloyd Dorsey, a spokesman for the Greater Yellowstone Coalition, said the fact the disease did not turn up in samples of deer and elk taken this fall is good news, but he hopes the Game and Fish Department will continue to augment its testing program in the coming year.

"The bad news is that they appear to expect chronic wasting disease to move into the wild game populations of western Wyoming sooner or later," Dorsey said. "We have good information now that should prompt the phasing out of these artificial feedgrounds in order to protect these treasured wildlife populations."

The general belief among most conservation groups and many wildlife biologists is that if chronic wasting disease were to spread to feedground elk, the disease would be transmitted through the populations at much higher rates than in normal, "free-ranging" herds, because the animals are artificially concentrated on feed lines in the winter.

Relatively little is understood about the spread of the disease, however. In some free-ranging mule deer herds in Wyoming, where the disease is endemic, nearly one-third of the animals are infected with chronic wasting disease, Kreeger said.

In other herds, where the disease has also long been present, the infection rates are much lower.

Game and Fish Department officials have repeatedly said it is the agency's long-term goal to eventually phase out elk feedgrounds, but that idea faces strong opposition from many ranchers and some sportsmen's groups.

Wintertime elk feedgrounds help reduce the intermingling of elk and cattle. Elk in the greater Yellowstone region are known to carry brucellosis, a disease that can infect domestic cattle

Groups such as Sportsmen for Fish and Wildlife oppose the phasing out of elk feedgrounds because they believe it would lead to mass starvation in the state's iconic elk herds and ultimately decimate the animals' numbers.

Kreeger said the Game and Fish Department's long-term research into chronic wasting disease continues. Other agencies in the U.S. are also conducting research on the disease. Until a great deal of data are compiled and analyzed, however, predictions about the future spread of the disease are speculative, at best, he said.

Environment reporter Chris Merrill can be contacted at chris.merrill@trib.com or 307-267-6722.