Montanans are entering an era when big game hunting may never be quite the same.
This fall, chronic wasting disease was detected in hunter-killed deer in two areas of Montana — south-central Montana’s Carbon County and north of Chester along the Hi-Line. It’s likely that many other deer, and possibly elk or moose, are also carrying the disease. They just haven’t been tested.
As the state’s wildlife managers scramble to determine the extent and prevalence of the illness through regional testing of hunter-killed deer and targeted hunts, it’s a good time to learn more about the disease’s infectious agent, how CWD has affected our Wyoming neighbor to the south and Montana’s future prospects.
“It will be interesting to see how things play out in Montana,” said Bryan Richards, emerging disease coordinator at the U.S. Geological Survey’s National Wildlife Health Center in Madison, Wisconsin.
“If you don’t get on it real early and real hard, you’ll have it for a while.”
Only New York, where CWD infections in two deer were identified and steps were taken to halt the disease’s spread, can wildlife managers say they have successfully eradicated chronic wasting disease.
With Montana surrounded on three sides by CWD — Wyoming to the south, North Dakota to the east, and Saskatchewan and Alberta to the north — the chances that a sick animal could migrate into the state make eradication a challenge. One thing in Montana’s favor, though, is that it does not have any game farms, many of which have seen outbreaks of CWD.
For 46 years Jeff Muratore has been hunting deer in the foothills, mountains and prairies near his home in Casper, Wyoming. Since the mid-1990s that region has been known to contain deer infected with chronic wasting disease, one of the longest-known infections in the United States.
Although the disease is now prevalent in the Casper region, and has spread north to many other areas of the state, Muratore said he has noticed no decline in the number of hunters.
“Just the opposite,” he said. “There are as many or more (people) hunting as before CWD was detected here.”
Two special hunts offered in Montana this winter to gauge CWD prevalence were surprisingly popular, with licenses selling out quickly and hunters traveling from as far away as Minnesota and Washington to take part, in spite of the fact that their animal could test positive for CWD.
“That’s all very encouraging,” said John Vore, Game Management Bureau chief for Montana Fish, Wildlife & Parks, since hunter participation was an unknown.
Muratore said hunter interest may remain high because there’s never been a documented case of CWD infecting a human who consumed meat from a sick animal.
“Once that happens, everything will change,” he said.
Muratore became more concerned about human contraction of CWD after news stories this summer reported a Canadian study that began in 2009 had documented that two out of five macaque monkeys contracted CWD after being fed deer meat from whitetails known to have the disease but that looked healthy. Another macaque got sick from eating brains from infected deer.
After more than five years all of the monkeys suffered from anxiety, movement problems and wasting, said Stefanie Czub, the study’s lead researcher and a professor at the University of Calgary’s School of Veterinary Medicine. When killed and examined, the three monkeys had lesions on their spinal cord, she said. The study’s findings may be published by June.
It is the first documentation of the illness jumping to another species biologically similar to humans.
“The macaque studies being done are not at all conclusive yet,” said Byron Caughey, who specializes in CWD research at Rocky Mountain Laboratories in Hamilton, a National Institutes of Health lab.
A study at the Hamilton lab using macaques found that CWD wasn’t transmissible, although squirrel monkeys were highly susceptible. That study was published in 2014. But Czub said her lab’s use of younger animals, longer incubation times and more sensitive tests that examined the spinal cord and not just the brain account for the different results.
The early results of the Canadian research were reported widely enough that it caught the attention of many hunters, especially since CWD has now been found in 21 states and two Canadian provinces.
“I do know more people are concerned about having their animals tested now,” Muratore said.
What’s a prion?
CWD is caused by a very tough customer, proteins called prions (pronounced pree on) that are capable of surviving in the soil for years, maybe decades. Once contracted by deer or elk, the animals shed and spread the proteins across the landscape through saliva, feces and urine for as long as they are alive. Prevalence rates in deer-rich southern Wisconsin are as high as 50 percent among whitetail bucks age 2 ½ and older, Richards said. When they die, the infected animals’ carcasses leach prions into the soil, plants, and water and can also be spread through scavengers that feed on the sick animal’s flesh.
“It’s about the toughest pathogen known to man,” Caughey said.
Caughey advised hunters who butcher their own meat to take precautions, like letting the parts of their grinder, cutting board and knives soak in a 5 to 10 percent solution of bleach for a half hour or more.
“There’s really no hard and fast rules on it,” Caughey said. “If the meat is dried on it can take longer.”
Putting infected game meat into a freezer after it has been cut up won’t kill prions, nor will cooking the meat. Prions are that tough.
But why bother if, as Caughey noted, there has never been a documented case of CWD in humans who became sick from eating infected deer or elk meat, despite several investigations?
“That doesn’t mean it doesn’t happen,” he said. “There’s just no compelling evidence yet. It’s probably a low risk, or we’d know about it loud and clear.”
The Centers for Disease Control and Prevention and World Health Organization think the risk is great enough to issue warnings, Richards noted.
“Why take that chance?” Caughey said. “I don’t think it’s worth the risk.”
Muratore has never had a deer he’s shot test positive for CWD — although he hasn’t had them all tested until this season. But if any animal does test positive he’s throwing the meat away, even if he’s spent hours cutting, grinding and wrapping the venison into neat white packets of steak and burger for the freezer. He’s not willing to take the risk.
Although Wyoming has had documented cases of CWD in wildlife for decades, there are no CWD-specific rules for wild game processors to segregate animals or for cleaning utensils and machines.
“Cleaning everything up each time would get expensive,” said Brad Wagler, a Cody, Wyoming, butcher.
Hanging animals for what may be two weeks, until test results come back, isn’t reasonable during the busy hunting season when space is at a premium in his meat locker.
Wagler did process one animal this year before its test results came back positive for CWD.
The hunter decided to throw the meat away, but still had to pay the processing fee, which Wagler said he discounted out of pity. A normally processed deer costs $125. The one that was thrown away cost three times as much because the hunter had a large portion turned into snack sticks.
The disease issue also raises questions about the donation of wild game meat to food banks. Will they now take only deer that have been tested and proven CWD-free?
“Most of those (processors), and rightfully so, won’t take an animal that’s tested positive or from an area that has animals that have tested positive,” said FWP’s Vore.
He said the decision is up to meat processors to decide how they work. “We can’t tell them what to do.” Missoula's large food bank is waiting for FWP to advise them.
Since there’s never been a case of CWD in humans, hunters may have a hard time imagining how it would affect a person. But it turns out CWD has symptoms similar to other diseases that many people have had a personal experience with: Alzheimer’s and Parkinson’s. In fact, the same Canadian lab that’s studying prions in CWD is looking at the disease’s similarities to Alzheimer’s — how the prions transform and attach themselves to healthy proteins causing neurological degeneration.
“Prions are a strange class of infectious agents,” Caughey said. “They have no genes of their own. They are corrupted aggregated forms of what would otherwise be a normal part of our body.”
There’s at least one incident where a prion-based disease has made a jump from animals to humans. In 1995 British cattle were fed rendered sheep that had scrapie — another prion-related neurodegenerative disease. The cattle contracted mad cow disease, which they transferred to humans who died from Creutzfeldt-Jakob Disease. That’s why those who donate blood are always asked if they or a family member have ever been diagnosed with CJD.
“It can be a very slow disease, an incubation period in excess of 40 years,” Caughey said, meaning that people may die of old age or other diseases before CJD becomes obvious. But that’s not always the case.
For his part, Muratore is not willing to take the risk, but he can understand why others aren’t so cautious.
“I guess we go on the highway knowing we could get in an accident and die,” he said.
Because CWD was first detected in Colorado and has spread to so many other states, wildlife managers have tried several ways to halt the disease’s spread. In Wisconsin, hunts to reduce deer numbers did cut CWD prevalence, but hunters got angry because there were fewer deer.
Montana is considering hunts in geographically small areas where CWD infection rates are high — like a farm field where a center pivot is drawing deer — to reduce local wildlife populations, FWP’s Vore said. The state also could work with landowners to move attractants like haystacks.
Such work won’t be cheap. In Wisconsin, CWD surveillance and all that entails amounts to a financial hit of about $100 per animal tested, Richards said. In 2002 when CWD was first detected in Wisconsin more than 40,000 deer were tested to determine prevalence. By 2015 that number had dropped to just over 3,100.
Scientists have already created a vaccine, which required an intense inoculation regimen. They are also working to find a test that could be used on live animals, as well as studying different types of soil to see if some are less favorable to CWD. So far, it appears the disease cannot be contracted through the skin, but hunters are still urged to use latex gloves when gutting and processing their animals.
Some believe nature may solve the problem.
In the past four years Muratore has seen mule deer numbers rebound in his hunting area, making him think that maybe some animals are becoming more genetically resistant to CWD.
“Possibly nature may find a way to get by this crisis, but no one knows for sure,” he said.
Deer population levels haven’t declined from CWD in the short term, said Richards of the USGS, but in badly infected areas where CWD has been around for years “there’s a history of population level impacts.”
“Over time there could be genetic selection for resistance to chronic wasting disease,” Caughey said.
Even resistant deer will die eventually, though, so during the course of their longer lives they would still be shedding prions into the environment.
“Those most susceptible are dying really fast,” Caughey said. “And the disease is really spreading rapidly in North America, and now Europe and Korea.”
Scientists are already successfully breeding sheep that resist certain strains of scrapie, but that’s in a captive environment, not the wild.
So the issue may come down to how fast scientists can react.
“Chronic wasting disease is so insidious and invasive, and it affects the population so dramatically, that there’s fairly rapid selection,” Caughey said.
Wildlife populations tend to ebb and flow for many reasons: drought, harsh winters, loss of habitat, blue-tongue disease in whitetails and a 15-year cycle of high and low populations that mule deer follow.
“I’ve seen it all,” Muratore said. “From the glory years when you see hundreds of deer in one day to when you’re lucky to see 10. It’s disturbing.”
For hunters in Montana, just now getting used to the idea of CWD spreading across the vast state, Muratore has this solemn warning.
“There’s no way you’re going to stop CWD in Montana,” he said. “The argument’s been made to increase the harvest to slow down the spread, but it won’t stop it.”
“Once it is established in a free-ranging population you will have it for a long, long time.”