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CWD expert: Wolves and hunters can help minimize spread of deadly protein

Dec. 9, 2021 Updated Thu., Dec. 9, 2021 at 6:58 a.m.

Computer modeling shows chronic wasting disease can be brought down to almost undetectable numbers when healthy wolf numbers are in the area preying on deer and elk.  (SSR)
Computer modeling shows chronic wasting disease can be brought down to almost undetectable numbers when healthy wolf numbers are in the area preying on deer and elk. (SSR)
By Eric Barker Lewiston Tribune

LEWISTON – Idaho’s most controversial predator could play a role in managing the spread of a deadly deer and elk disease, according to a leading research scientist.

Margaret Wild, a professor at Washington State University’s College of Veterinary Medicine, studied chronic wasting disease in Colorado for three decades before moving to Pullman in 2018 to head the school’s elk hoof disease research team.

Chronic wasting disease, a fatal and contagious illness affecting deer, elk and moose, was detected near Lucile, Idaho, earlier this fall. It is the first time the feared illness, that can reduce herd numbers and has a low potential to affect human health, has been documented in the state.

Idaho Department of Fish and Game officials started emergency hunts this week designed to collect samples so they can determine the prevalence of the disease. Wild said that is a good and necessary first step and commended the agency for its previous testing efforts that detected two mule deer bucks with CWD in Unit 14, that stretches from Cottonwood to Riggins.

Nip it in the bud

Once the prevalence is known, the agency can move to actions designed to contain the disease or at least reduce its spread. Wild said hunting is a good tool wildlife managers can employ, but wolves may be particularly effective at containing the disease.

While working in Colorado, Wild and others used a computer model to simulate the effect of wolf predation on CWD.

“We showed hunting can help keep the prevalence of chronic wasting disease somewhat in check, but selective removal of deer by a coursing predator like a wolf actually really brought the prevalence of chronic wasting disease down in these populations and got it down to almost undetectable levels.”

Wild emphasized the work wasn’t a field study but rather computer modeling. Nonetheless, she believes healthy wolf numbers in areas with CWD can be a crucial tool.

Wolves test their prey by chasing and, when available, show preference for deer and elk that are ill or injured.

Chronic wasting disease is caused by misfolded proteins known as prions. It can take a year or two for an animal to die from the disease, but all the while, the sick animals are shedding infectious prions that persist in the environment for years like disease booby traps.

“It’s not a bacteria, it’s not a virus, it’s not a parasite,” Wild said. “It’s a protein and it doesn’t degrade easily at all.”

Wild said those that are infected are likely to have symptoms which, even in the early stages of illness, make them less wary, and less able to avoid predators, long before the disease progresses to the point of death. So wolves, by the way they hunt, are likely to single out these animals and remove them long before they would have succumbed to the illness.

“If they take them out six months or a year earlier than they would have died, it can reduce all those potential transmission events,” she said.

Wolves and other canines are not susceptible to the illness and thus are unable to spread it.

“My suggestion would be to consider increasing tolerance for wolves in these areas, because we know they selectively remove animals that are easy targets,” she said.

Starting Tuesday, Idaho hunters can purchase special tags allowing them to hunt deer in and around Unit 14 as part of an Idaho Department of Fish and Game effort to measure the prevalence of the disease. More information is available at idfg.idaho.gov/cwd/hunt.

Slow-motion epidemic

Wild said CWD, like most wildlife diseases, is difficult to control and nearly impossible to eliminate. Early detection can help. She said New York wildlife officials appear to have stopped the disease by reducing deer numbers following early detection. But that has been the rare exception. More commonly, the disease is not detected until it attains a level of prevalence that prevents elimination.

“It’s an epidemic but a slow-moving epidemic,” she said. “It happens in slow motion because the disease is slow to progress in the animals. It usually takes a year to a year and a half for an animal to show clinical signs.”

That makes early detection more difficult.

The degree to which it reduces deer and elk numbers depends on multiple factors such as prevalence, how long it has been present, density of deer and elk, geographic range, predator levels, hunting pressure and environmental conditions.

“There are areas we have certainly seen population level effects on whitetail, mule deer and elk,” she said.

It tends to be less prevalent in elk compared to deer, but in places like Rocky Mountain National Park, where elk density is high and there is no hunting, a higher percentage of animals tend to be infected.

Prevalence in deer and elk herds can range from less than 1% up to the midteens. Wild said the prevalence in and around Unit 14 is likely on the lower end but said it wouldn’t be surprising to find it as high as 5%.

Human health

The disease has never been shown to jump from deer or elk into humans. But a similar prion-caused neurological disease in cattle – bovine spongiform encephalopathy, or mad cow disease – does occasionally infect humans who eat infected beef. In contrast, scrapie, a similar neurological disease in sheep, has been around for hundreds of years and never made the leap to humans.

Because mad cow disease can make the jump on rare occasions and a study that indicated CWD may be able to jump from humans to macaque monkeys, health agencies like the Centers for Disease Control and Prevention advise people not to eat the meat of animals with CWD.

Wild said hunters should always use good hygiene when field dressing or butchering wild game. That includes wearing gloves, avoiding brain and spinal cord tissue and washing knives and other equipment in a bleach and water solution. She also said they should have their animals tested, but she noted animals in the early stages of the disease may not have enough prions accumulated in their lymph nodes to be detected

.

What people can do

Wild said there are several things people can do to help slow the spread of CWD. They can tolerate higher wolf numbers and not feed deer and elk. Feeding concentrates animals and accommodates disease spread. People also should report obviously sick deer and elk to wildlife agencies. Hunters also can help to not spread the disease by disposing of deer and elk carcasses properly and by not moving carcasses long distances.

“If I hunt in one area and move an animal 100 miles to my home and toss the carcass in the back 40, if it is CWD positive, I just contaminated a new area,” Wild said.

Last, they can continue pursuing deer and elk. Wild lived in northern Colorado, the epicenter of CWD in the state, for more than 30 years and raised her family on wild elk.

“If you hunt, continue to hunt. Hunting is one of the best management tools we have right now. And consider having your animals tested for CWD. Even though it’s not a food safety test, it really helps managers with surveillance.”

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