Two days before Christmas, disease biologist Jared Rogerson responded to a report of a sorry-looking buck mule deer in a fringe Pinedale neighborhood.
“It was alive, but it was just very sick and laying down and not interested in moving,” Rogerson said. “And it was really emaciated.”
The Wyoming Game and Fish Department staffer put the distressed animal out of its misery. A necropsy showed the buck had pneumonia, and weeks later testing at the agency’s Wildlife Health Laboratory in Laramie showed he had been worn down by degenerative chronic wasting disease — just the third-ever case of the incurable encephalopathy being confirmed in Wyoming’s portion of the Green River basin. A deer tested positive in residential Green River in 2012, and then it took five years for the next detection, marked near Pinedale’s Ralph Wenz Field Airport in 2017.
Other parts of Wyoming grappling with the recent arrival of the worrisome wildlife disease are seeing many more cases.
Game and Fish officials were surprised to see a flare-up of CWD this last fall in its deer hunt unit No. 105, which stretches from Yellowstone National Park to Badger Basin near the border of Montana — another state that’s scrambling to ascertain where the disease is occurring. Although the prion malady had never been known to occur in deer hunt area 105, five bucks shot and bound for freezers last fall and another that was road-killed tested positive out of 16 total deer tested from the area.
“That was a lot, because it was the first year we detected it up there,” Wildlife Health Lab Supervisor Hank Edwards said. “So that was a surprise to us.”
Edwards said he wouldn’t read much into the prevalence rate — which amounted to nearly a third of deer tested — because of biases that lead to likely infected animals being tested at higher rates.
“What happens is sometimes a hunter will shoot an animal and go, ‘Holy s---, that thing is really thin,’ and they’ll submit it when they wouldn’t test it otherwise,” Edwards said. “That really affects your data.”
Other swaths of the state where CWD has only recently arrived are experiencing suddenly widespread, routine detections that are more statistically significant.
Deer hunt zone 157 — which stretches from Riverton to Pavillion to the Owl Creek Range to Boysen Reservoir — is the case in point. This past fall, Game and Fish dubbed the unit one of its inaugural CWD surveillance focus areas. The state agency’s Lander Region brought on technicians whose job was laser-focused on collecting lymph nodes and other tissues telling of the disease. They even sent out letters to hunters with an appeal to submit samples.
Some 70-plus mule deer samples and another 50-plus whitetail deer samples arrived at Edwards’ lab. Unfortunately, over half the animals hunters harvested were coming up positive for CWD — and in a unit that was first confirmed positive as recently as 2012.
“It’s alarming that it’s that high, for sure,” Edwards said. “This was an area where we just didn’t have much data.”
“Deer hunt areas 105 as well as 157 are both good examples of the fact that we’re just starting to get caught up on our surveillance and get a good handle on where CWD is existing and at what prevalence,” he said.
Jackson Hole to date has just a single positive detection, although the Jackson Elk Herd is easily the most closely surveilled ungulate herd in the Equality State.
Other reaches of the state along the leading western edge of the CWD endemic area have also held steady with a single detection or very few.
The deer hunt area encompassing Star Valley joined the CWD endemic zone in 2016, when a stricken doe mule deer found dead tested positive. A total of just 10 samples have been submitted by hunters in that area in the past five years, Edwards said, and none have tested positive. But that’s a statistically insignificant sample size, he said.
Deer hunt area 152, which encompasses the northern Wyoming Range’s celebrated mule deer population, joined the CWD-positive ranks just this fall when a hunter had his animal sampled at the Alpine check station. A second animal registered as positive later in the year, although relatively few samples from the zone have been submitted, Edwards said.
Game and Fish’s new surveillance program, which focuses resources on collecting tissue samples from specific ungulate herds, is designed to end ambiguities around CWD’s distribution and occurrence rates.
“We’ve got a fair amount of work to do,” Edwards said. “Within, hopefully, five years, we should have a good handle on our prevalence.”
The surveillance format is new in 2019 and was recommended by a working group that helped reconfigure Wyoming’s CWD plan, which is likely to be finalized this spring. Nine to 11 deer and elk herd units will be selected annually as focal herds, with a goal of gathering 200 samples apiece.
“We can’t just continue to do a shotgun approach across the entire state,” Edwards said. “Then it’s all like, ‘seven samples here, 10 samples there.’ We want those 200 samples.”
In the Pinedale hunt area where the second positive deer turned up near death over the holidays, hunters had turned in just seven samples since CWD reached the area in 2017. Last hunting season, only two samples trickled in.
Pending thorough testing, CWD prevalence near Pinedale remains to be seen. But to Rogerson, the disease biologist, it’s worrisome that even a couple of cases have been confirmed.
“It’s concerning to have the disease arrive,” Rogerson said. “Especially in areas where we know we have a lot of deer interacting.”