Aaron Skarlupka, a hunter in northeastern Wisconsin, was thrilled recently when he got his first harvest of the season: an eight-point whitetail. Skarlupka’s son, who was out hunting in the forest on a cold morning, convinced his father to mount a prominent head so he could hang it on his bedroom wall.
Taking care to avoid glands that may have scars chronic wasting disease (CWD) — a 100 percent fatal disease of deer, elk and moose that has been detected in 35 U.S. states and five Canadian provinces — Skarlupka donned a pair of nitrile gloves and carefully cut up the carcass. Some hunters in the area gave him grief about the gloves: “I definitely got some pushback and ridicule,” he says, “and some are like, ‘What are you doing?'”
How CWD could have spread to humans or the science behind it is murky. Until now it has not been a documented case in a human, but scientists say people who eat contaminated game meat like venison may still be at risk. Some hunters like Skarlupka are reluctant to take risks, especially when they depend on venison to feed their families. The other hunters don’t care.
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Constantly research continues to reveal new aspects of the diseasehelping scientists understand more about cross-species infection and the potential of vaccines. However, skepticism and misinformation about the legitimacy of the CWD threat abound in Wisconsin and elsewhere. Potential management policies are mostly shelved. All Wisconsin can do for now is control the disease as it spreads across the state, county by county. The Wisconsin Department of Natural Resources (DNR) relies on tissue submissions from hunters, but only about 10 percent of the state’s hunters submit their deer for testing. And even when they do, a DNR survey found that a quarter of the contaminated meat is taken home and eaten anyway.
CWD is not caused by a typical virus or bacteria. It is caused by a prion: a misfolded protein causes other proteins to fold abnormally, killing cells by spreading a network of cellular destruction that leads to a slow and undignified death. Prion diseases, such as CWD, mad cow disease and Creutzfeldt-Jakob disease they are usually spread by ingestion, inhalation or oral route. When a deer licks the saliva, feces, or blood of an already infected animal, a prion slips into the body and begins its slow, deadly campaign.
As misfolded prions encounter healthy cells that have functioning prions inside, they turn the prions into misfolded infectious agents, and “that’s what’s happening,” says Jason Bartz, a microbiologist at Creighton University. The wave of prions slowly accumulates, spreading through the spleen and lymph nodes and from the peripheral nervous system to the central nervous system. Misfolded proteins inside some cells don’t cause problems, Bartz says. But in other cells, especially neurons in the brain, a misfolded prion is a death sentence. As CWD prions accumulate in the host’s brain and spinal cord, the increasing destruction of tissue and cell function eventually and invariably leads to death.
Deer can survive with CWD for years without showing any noticeable symptoms. In the later stages of the disease, the deer become starved, weak and less afraid of humans. They are often killed by predators, cars or guns before the disease is completely gone. Some researchers fear that CWD could permanently weaken US deer herds
So far, humans have been spared. “There is no evidence of transmission of chronic wasting disease to humans,” says Ermias Belay, a medical epidemiologist at the US Centers for Disease Control and Prevention. But just because there’s no evidence now doesn’t mean there never will be. Because prion diseases can have long incubation periods, from years to decades, during which misfolding can spread without obvious symptoms, “it is very important to monitor the potential transmission of the disease in humans for a very long time,” Belay added. “Continued vigilance in follow-up is key.”
CWD was first identified in northern Colorado in the 1960s, and Wisconsin found its first case in 2002. Almost immediately, the state sent in shooters and hunters who killed thousands of deer in the southern prairies of the state, where CWD was prevalent. The DNR cracked down on hauling carcasses, and in some counties, instituted the Earn-a-Buck program, which required hunters to harvest a doe before “earning” the right to buck. Killing female deer weakens the herd’s ability to grow, and officials believed that thinning deer herds was key to eradicating the disease and preserving the health of the wild herd.
Some hunters believe Earn-a-Buck was one of the DNR’s “greatest tools” in fighting the disease. Others saw it as a major violation of their hunting traditions, says Kim Zuhlke, president of the Coulee Country Branch of the Deer Association, who has hunted in southwestern Wisconsin for more than 60 years.
A similar method of aggressive deer management worked in New York State, the only state that has successfully eradicated the disease in the wild But Wisconsin hunters refused to fully buy into the crisis that CWD seemed to threaten. Hunting, after all, is almost sacred here. For many hunters, the thinning of herds for no justified reason – as they saw – caused trouble, Zuhlke says. He says harvesting more deer, sending samples and meeting the restrictions was a huge hurdle, and it was difficult to create a sense of urgency.
“Over time, many hunters came to recognize that the cure was worse than the disease,” says Wisconsin DNR social scientist Ben Beardmore, who has studied hunter attitudes toward CWD management. “And for every year that passes after someone eats contaminated meat and doesn’t become infected with CWD, the perception of risk goes down.”
Eventually, the state shut down programs like Earn-a-Buck and changed its stance on CWD from controlling the spread of the disease to controlling it. Different regions, different zip codes, and different family members still hold conflicting opinions about the threat CWD poses to human health and Wisconsin’s wild deer. It is difficult to rally a community against a disease that dies slowly, almost imperceptibly, without much fanfare.
“I see it from a hunter’s point of view: you go in, you see a herd, and they look beautiful. Nobody looks sick. And so you’re thinking, “Well, there’s nothing wrong with this herd,” says Candace Mathiason, a pathobiologist specializing in CWD at Colorado State University, who is conducting CWD vaccine research in deer. The disease may not be in a particular herd, but “if there’s CWD there, they’re passing it on to each other,” says Mathiason, who has stopped hunting in part because of the threat of CWD.
Mathiason’s work has shown that CWD prions can spread between deer, elk, moose, and reindeer through saliva, feces, and blood. Prions can be passed from pregnant deer to their unborn fawns and have also been shown to bind to soil, suggesting that deer can become infected through their environment.
However, some research suggests That CWD could have evolved to infect new species or jump to people through other animals. If the disease jumped from deer to pigs, for example, it might jump from pigs to humans. “I think that’s an important issue, especially since there are large pig populations where CWD is moving into areas of the southern United States,” Bartz says.
While the risk of transmission is low for now, some people see the stakes as high. “Personally, I’ve tested every deer I’ve shot,” says DNR social scientist Lauren Bradshaw, who has studied how Wisconsin hunters think about the disease. The Wisconsin DNR advises hunters to taste meat before consumption. “Even if the risk was 0.005 percent,” says Bradshaw, “I don’t want to be patient zero.”
