5 cases of ‘zombie deer disease’ confirmed just miles from Idaho-Montana border

This spring, Montana wildlife officials confirmed five cases of a deadly neurological disease less than 25 miles from the Idaho Panhandle.

Chronic wasting disease, which can decimate deer and elk populations, was first confirmed in and around Libby, Montana, in May.

The confirmations will likely trigger year-round monitoring efforts in the Idaho Panhandle, said Toby Boudreau, the wildlife bureau chief for Idaho Department of Fish and Game.

“I imagine that is the direction that we will go,” he said.

IDFG already does year-round surveillance in the southeastern region of the state. That surveillance effort started in July 2017 after a mule deer in Wyoming’s Star Valley tested positive for CWD the year prior. The deer was 1 1/2 miles from the Idaho border. Other close calls include a 2010 confirmation about 5 miles from the Idaho border in Bedford, Wyoming.

There have been no confirmed cases of CWD in Idaho or Washington.

Still, the Libby CWD confirmations are big news for regional hunters, wildlife managers and conservationists. For the first time, CWD has been documented west of the Continental Divide, according to a Montana Fish, Wildlife & Parks news release. Montana officials don’t know how the disease spread to Libby.

“This last Libby thing was definitely news to us,” Boudreau said.

Zombie deer

CWD is a debilitating neurological disease that kills deer and elk, similar to bovine spongiform encephalopathy, or mad cow disease. There is no known cure.

Infected animals will, among other things, stumble, drool, show no fear of people and lose weight.

While some research indicates CWD can jump to other species, including primates, there has never been a human case of CWD.

The disease is spread via “abnormally formed proteins” known as prions. CWD has a long incubation period, meaning seemingly healthy animals may be infected, and prions spread to the soil via deer or elk scat, urine and saliva can remain infectious for years.

CWD was first documented in Fort Collins, Colorado, in 1967. Since then it has spread, decimating cervid populations in some states. A Wyoming study documented a 21% annual decline in mule deer herds with extinction within 40 years.

Idaho’s response

The severity of CWD all comes down to the prevalence in the population, Boudreau said. While the disease is nearly impossible to stop, its spread can be slowed.

“States have reduced the prevalence on the landscape,” he said. “We haven’t cast in stone any prescription for what will happen, because ultimately deer and elk populations are a public resource and we will manage them as the public desires.”

The current surveillance strategy used by IDFG includes collecting samples from hunters and roadkill and responding to reports of deer behaving abnormally. The sampling model gives IDFG a 95% chance of detecting CWD if 1% of the population is infected.

Idaho first started testing for CWD in 1997 and has sampled around 16,000 mule deer, white-tails, elk and moose. Those samples are sent to an out-of-state lab.

Boudreau estimates IDFG spends less than $100,000 per year statewide on surveillance efforts.

In 2018, the state updated its CWD response plan, the third such plan IDFG has drafted. Additionally, last year the Idaho Fish and Game Commission banned the import of deer, elk or moose carcasses and urine from areas with documented cases of chronic wasting disease.

“We’re doing a better job,” Boudreau said. “I think science has come a long ways with surveillance and testing. I think Idaho is definitely better prepared.”

Different state, different story

That sort of widespread surveillance is not occurring in Washington. Since 2011, the Washington Department of Fish and Wildlife has not had a “formal surveillance program,” said Kristin Mansfield, a wildlife veterinarian for WDFW.

In 2011, funding provided by the federal government (to Washington, Idaho and other states) ended. WDFW still does “targeted surveillance” and responds to reports of odd deer and elk behavior.

Mansfield hopes that changes.

“There are currently several bills in Congress, some of which would be really beneficial to our agency and other states to restart our surveillance program,” Mansfield said.

Like Idaho, Washington has done some CWD testing since 1995. The state banned deer farming in 1993.

“Fortunately, Washington had the foresight, in the mid-1990s, to mostly ban deer farming,” she said. “I have no doubt that if we still had deer farming, we would more than likely have CWD.”

There are also strict rules governing the importation of carcasses from states with documented cases of CWD, although Washington doesn’t have any rules banning the use or importation of urine.

This fall, Mansfield and others will start working on updating the state’s response plan. They hope to have a draft done by December. An updated plan could make it easier to apply for surveillance funding, she said.

“We would like to implement a good surveillance plan that meets scientific criteria,” Mansfield said.

Wildlife managers from both states urge hunters and others to report animals that appear sick and to not bring “high-risk parts from positive states.”

“I think there is a good chance we can keep it out of the state,” Mansfield said. “But we really need to address things more aggressively than we have at this point.”

The signs of CWD

Deer and elk with chronic wasting disease appear emaciated, don’t avoid humans and can act listless and unresponsive.

In Idaho, hunters are encouraged to stop at check stations during the season and submit samples from their animals. Idaho Department of Fish and Game biologists collect lymph nodes from harvested and salvaged animals. If you harvest a mule deer in one of the game units where samples are being collected, head to the nearest check station or the regional office. If bringing a sample into a regional office, leave the upper portion of the neck attached to the head so that staff can remove the lymph nodes from the throat. Only adults and yearlings, no fawns.

The same holds true for any salvaged road kill.

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