Everything You Need to Know on the Impacts and Spread of CWD

There is a growing concern regarding the presence and spread of the degenerative brain disorder, chronic wasting disease, and the possibility it may spread to humans through consumption.

The disease has never been shown to infect humans who consume CWD infected meat, but a recent study in Canada by the Canadian Food Inspection Agency found a group of captive macaque monkeys contracted the disease after consuming infected whitetail deer meat. It was the first time CWD was ever recorded infecting a primate. The study now raises more concern for the spread of the disease to humans. CWD destroys the brain of hoofed animals like deer, elk and moose and is similar in nature to mad cow disease, which does transmit to humans.

According to Matt Dunfee of the CWD Alliance research center, the disease involves proteins, found in every mammal called prions, which can stimulate irregular protein formations in the brain. The mal formed proteins then replicate and over the course of several years destroy brain and nervous system functions.

Dunfee said the disease is particularly hard to understand, because it involves proteins and not bacteria or viruses. Infected animals constantly shed the mal-formed prions through natural bodily fluids and uninfected animals can pick up the prions from the earth and the prions will begin to change every normal prion they come into contact with. The infection will then cause tissue changes in the  brain, neurological damage, strange behavior and inevitable death.

CWD was first discovered in 1967 in captive mule deer populations near Fort Collins Colorado, then in wild elk in ‘81 and is now documented in 24 states and two Canadian provinces in wild, or farm raised, deer and elk and even moose in Colorado. What biologists don’t know, however, is where the disease came from, or how it started.

Map depicting where CWD is present in North America

Photo courtesy of the CWD Alliance

Dunfee said the disease could have always existed, but was never noticed, somehow spontaneously generated, or is an offset from the similar disease scrapie, which is found in domestic sheep.

Dunfee said the disease is slow moving, but what makes it hard to manage is its incredible longevity. He said infected prions can survive in an animal carcass for two years and live in the soil for potentially longer.

“This is a disease you measure in decades, not years,” he said.

Because of the 100% fatality rate and no known vaccine, management options are limited.

According to Dunfee, Wyoming took an observational stance when the disease was discovered and is now dealing with higher infection rates and significant herd loss in whitetails and mule deer in the eastern portion of the state. Dunfee said if you shoot a deer in eastern Wyoming and want to know if it has CWD, all you need to do is flip a coin.

On the other end of the spectrum, however, the Wisconsin Department of Natural Resources opted for culling their deer herds where CWD was most concentrated.

onX Hunt Team member Trevor Olson said the deer population on his family farm in Wisconsin has dropped by almost 75%. He said his memories of the early 2000s are of deer check stations and the earn a buck program, where you had to shoot one or more doe before earning a buck tag, and truck beds stacked with deer.

Olson said the effects of the cull have made him far more selective with his deer hunting to the point of agreeing with neighboring farms to not even rifle hunt until they saw a rise in populations. Olson has even avoided hunting the family farm in an effort to see repopulation take place. He said the past few years have been better for numbers, but he still feels the deer are still at a pre CWD population level.

Olson said there is a general disapproval among hunters on how the state managed the  outbreak and he fears the old days of hunting in Wisconsin aren’t coming back.

“Those traditions are long gone,” he said.

Unlike Wisconsin’s large scale cull tactic, Illinois is taking a more balanced approach by focusing on selective culling and controlling targeted populations to reduce the spread.

Whitetail deer in field

The disease was most recently discovered in Arkansas in 2015, instituting new precautions by the state department of game and fish. onX team member Matt Gray lives one county south of the highest concentration of the disease. He said while his home area in Pope County has only seen two confirmed cases, Newton County saw over 160 infected animals since the discovery. Gray said when CWD was first discovered, the department of game and fish created a  five mile perimeter and euthanized every deer within it. When infected animals were found outside that perimeter, however, the department was forced to expand the perimeter to ten miles and then even wider.

Now people are instructed to avoid harvesting sick looking deer and report them immediately to game and fish. The only problem is, most deer suffering from the disease will begin to lose nervous system functions and most likely be killed by predators, or even cars, before the visible signs of emaciation take hold.

“It opened our eyes around here,” Gray said.

Gray is more aware of the disease now, but even the Canadian study won’t keep him from hunting his favorite spots. The outbreak is, however, affecting the game and fish hunting laws he has to follow.

Natural urine attractants are no longer legal in Arkansas because of the fear of spreading the disease from farm raised deer. Salt licks are only legal to spread between September through January instead of year round, because the disease tends to spread when deer congregate. Like in most affected states, you will also have to debone all your meat when transporting it from an infected county to a non infected county. For an added piece of mind, game and fish will also check game meat for the disease.

Back in Colorado, where the disease was first discovered, CWD has almost become integrated with hunting. onX team member, and member of Predator Quest, Curtis Elmore said it is in the back of your mind while you hunt, yet it still doesn’t keep him out of the field. Elmore knows there is no proof regarding the transmission of the disease to humans, but can’t help think about it when putting wild game on the table for his kids. With all that being said, though, it’s not going to stop him from hunting, and he has already reconciled that when he draws his coveted moose tag, it will undoubtedly be in a CWD zone.

Deer with CWD

Dunfee said that while the Canadian study on primates shows the interspecies disease barrier is not as strong as we thought, it still rather robust. He urges anyone concerned about eating wild game to call their local wildlife management agency and get the animal tested. The disease is only contracted from a concentration of prions, so aside from getting it tested he advices hunters to avoid brain tissue, lymph nodes, or sawing into the spinal cord, which are all places where prions congregate. You can also help yourself with general precautions like wearing gloves during field dressing, disinfecting your tools, or the skull with a bleach and water mixture. You can also contact local wildlife officials regarding transporting a harvested animal across state or county lines.

What Dunfee does not advise, though, is stopping hunting altogether. As a hunter himself, he frequently hunts CWD zones and deals with the uncertainty by getting his animals checked. He urges people to not shy away from their heritage, but instead hunt for the sake of managing the disease and the deer and elk herds. Most of the samples received for testing come from hunters and without those samples, Dunfee said it would be very difficult to further study the disease.

Whitetail deer at sunset

“Without hunters we will be sunk on managing this disease,” he said. “The wild populations of cervids (deer family) depend on it.”

Updated August 2018