Aaron Skarlupka, a hunter in northeast Wisconsin, was recently thrilled when he got his first harvest of the season: an eight-point white-tailed buck. Skarlupka’s son, who was along for the chilly morning hunt in the woods, convinced his dad to have the prominent head mounted so he could put it on his bedroom wall.
Taking care to avoid any glands that might contain traces of chronic wasting disease (CWD)—a 100 percent fatal illness in deer, elk and moose that has been in detected in 35 U.S. states and five Canadian provinces—Skarlupka put on a pair of nitrile gloves and carefully beheaded the carcass. A few nearby hunters gave him grief about the gloves: “I definitely got some pushback and ridicule,” he says, “and some looks like, ‘What are you doing?’”
The science behind how or if CWD could spread to humans is murky. So far there hasn’t been a documented case in a human, but scientists say that people who eat infected game meat such as venison could still be at risk. Some hunters like Skarlupka aren’t keen on taking chances, especially when they depend on deer meat to feed their family. Other hunters don’t care.
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Ongoing research continues to reveal new aspects of the disease, helping scientists understand more about cross-species infection and the potential of vaccines. Yet skepticism and disinformation about the legitimacy of CWD’s threat abound in Wisconsin and elsewhere. Potential management policies mostly sit on shelves. All Wisconsin can do for now is monitor the disease as it spreads across the state, county by county. Wisconsin’s 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 about a quarter of infected meat is taken home and eaten anyway.
CWD is not created by a typical virus or bacterium. It’s caused by a prion—a misfolded protein that causes other proteins to fold abnormally, killing cells in what can become an expanding network of cell destruction that leads to a slow and undignified death. Prion diseases such as CWD, mad cow disease and Creutzfeldt-Jakob disease are typically spread by ingestion, inhalation or by mouth. When a deer licks the saliva, feces or blood from of an already infected animal, a prion might slip into the body and begin its slow, fatal campaign.
As misfolded prions encounter healthy cells with functioning prions inside, they convert the prions into misfolded, infectious agents, and “that just keeps happening,” says Jason Bartz, a microbiologist at Creighton University. The wave of prions slowly accumulates, spreading through the spleen and the lymph nodes and through the peripheral nervous system into the central nervous system. Misfolded proteins inside some cells don’t cause problems, Bartz says. But in other cells, especially some neurons in the brain, a misfolded prion is a death sentence. As CWD prions accumulate throughout the host’s brain and spinal cord, the widening destruction of tissue and cell function eventually—and always—leads to death.
Deer can survive with CWD for years without showing noticeable symptoms. In the later stages of the disease, deer become starved, weak and less fearful of humans. Often they die from predators, cars or guns before fully wasting away to the disease. Some researchers fear that CWD could permanently debilitate deer herds across the U.S.
Thus far, humans have been spared. “There’s no evidence of any transmission of chronic wasting disease to humans,” says Ermias Belay, a medical epidemiologist at the U.S. Centers for Disease Control and Prevention. But no evidence now doesn’t mean no evidence ever. Because prion diseases can have long incubation periods, from years to decades, during which the misfolding can widen without any noticeable symptoms, “it’s very important to monitor the potential transmission of the disease in humans for a very long time,” Belay adds. “Continued vigilance in monitoring is critical.”
CWD was first identified in northern Colorado in the 1960s, and Wisconsin found its first case in 2002. Almost immediately, the state sent in sharpshooters and hunters who killed thousands of deer throughout the state’s southern grasslands, where CWD was most prevalent. The DNR cracked down on transporting carcasses, and on some regions, it imposed the Earn-a-Buck program, which required hunters to harvest a doe before they could “earn” the right to a buck. Killing female deer weakens a herd’s ability to grow, and officials thought that thinning out deer herds was the key to eradicating the disease and preserving wild herd health.
Some hunters think Earn-a-Buck was one of the DNR’s “greatest tools” to combat the disease. Others saw it as a major infringement on their hunting traditions, says Kim Zuhlke, president of the Coulee Country Branch of the National Deer Association, who has been hunting in southwestern Wisconsin for more than 60 years.
A similar method of aggressive deer management worked in New York State, the only state to have successfully eradicated the disease in the wild. But hunters in Wisconsin refused to fully buy into the crisis that CWD seemed to be threatening. Hunting, after all, is almost sacred here. To many hunters, thinning herds without a justifiable cause—as they saw it—created a hassle, Zuhlke says. Harvesting more deer, submitting samples and abiding by restrictions felt to them like a huge inconvenience, he says, and it was hard to create a sense of urgency.
“Over time, a lot of hunters perceived the cure to be worse than the disease,” says Ben Beardmore, a social scientist at the Wisconsin DNR, who has studied hunter attitudes toward CWD management. “And every year that goes by that somebody doesn’t get infected with CWD after eating infected meat, the perception of risk goes down.”
Eventually the state closed down programs like Earn-a-Buck and switched its stance on CWD from controlling the spread of disease to monitoring it. Different regions, different zip codes and even different family members still maintain opposing views on CWD’s threat to the health of humans and Wisconsin’s wild deer. It’s hard to rally a community against a disease that kills slowly, almost invisibly, without much fanfare.
“I can see from a hunter’s perspective: 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 might not be present in a given herd, but “if there’s CWD there, they’re passing it amongst one another,” 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 cervids such as deer, elk, moose andreindeerthrough saliva, feces and blood. The prions can pass from pregnant deer to unborn offspring and have even been shown to bind to soil, suggesting that deer can become infected through their environment.
Still, some research suggests that CWD could evolve to infect new species or jump to people through other animals. If the disease were to make a leap from deer to swine, for example, it might then jump from swine to humans. “I think that’s an important consideration, especially as CWD is moving into areas in the southern United States where there are large, feral swine populations,” Bartz says.
Although the risk of transmission is low for now, some people see the stakes as high. “Personally, I’ve tested every deer that I’ve shot,” says Lauren Bradshaw, a social scientist at the DNR, who has studied how Wisconsin hunters think about the disease. The Wisconsin DNR recommends that hunters test their meat before consuming it. “Even if the risk was 0.005 percent,” Bradshaw says, “I don’t want to be patient zero.”
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