Try to imagine a disease that has no cure and no immunity. It is always fatal. Diagnosis is a one-way ticket, but the disease does not kill immediately. It can take over a year before the infected host develops symptoms. The whole time the host is infected, it is unwittingly spreading the disease. The disease slowly bores holes throughout the host’s brain, and neurological function declines. Eventually, the host appears emaciated and staggers around as if lost. It has no fear of what it should be fearful of. Essentially, it appears dead inside. What was once vibrant and lively now only exists as a shell of its former self. The host is, for the most part, a zombie. This disease is not imaginary. It thrives in Wisconsin and continues to spread into other states. It’s called Chronic Wasting Disease (CWD).
First announced in 2002, CWD was discovered in the Wisconsin whitetail deer population and shook hunters to the core. Concerns of how CWD would influence the future of whitetail hunting and the closely held annual tradition raised many questions. Venison, the meat that comes from deer, is a primary source of protein for many Wisconsin families. This is especially true for rural areas, so confirmation of an infected animal does not always deter consumption. Some even ignore the advice given for deer harvested in confirmed CWD locations as if ignorance will protect them.
Motives for ignoring the advice range from needing the meat for food to a lack of concern. Testing of a harvested deer is voluntary and involves a lengthy process of sending the head into an agency and then waiting for the results. Some hunters do not care to invest the time necessary to test because the deer appeared healthy while it was still breathing. To deal with the environmental issues related to CWD, disease management objectives to limit the spread, reduce prevalence, and eliminate the disease must continue.
According to the Centers for Disease Control and Prevention (CDC), CWD is a prion disease that affects deer, elk, reindeer, sika deer, and moose. Unlike other diseases, CWD cannot be treated because the disease is not actually alive. A prion is a misfolded protein that is not readily broken down in the body. This leads to accumulation, typically in the lymphatic and neural tissues. As the misfolded proteins accumulate, they bore holes into the surrounding tissue. As a result, the brain tissue appears spongy. Figure 1 compares healthy brain tissue to figure 2, the brain tissue with CWD.
Upon contracting CWD, life expectancy is about 18 to 20 months. While the deer may appear healthy for the first 16 months, more and more holes accumulate in the brain. Once enough damage has been done, the deer begins showing signs like heavy drooling, tremors, staggering, and thin bony features covered by a ratty looking hide (figure 3).
There is no known evidence that CWD can transfer to humans. Still researchers are being cautious due to limited knowledge of the disease. CWD is one of the most contagious prion diseases. Moreover, CWD prions spread in urine, feces, and saliva, which is driving force of CWD transmission. Deer hunting and venison consumption are very common in Wisconsin. As the disease continues to spread, exposure of humans to CWD prions becomes more likely. The past has shown society that humans are susceptible to a different prion disease called bovine spongiform encephalopathy, or mad cow disease. There were many cases of mad cow disease in the United Kingdom during the late 1990s that affected people. The United States suffered four deaths related to consuming meat from cows with mad cow disease.
Although mad cow disease prions are different from CWD prions, the potential transmission to humans is an alarming issue and still an open question. A long-term study exposed macaques to CWD through the consumption of infected meat. The study found that three of five macaques fed infected deer meat over a three-year period tested positive for CWD. Macaques were chosen for the experiment because of how closely related they are to humans. The results verify what the Wisconsin DNR, CDC, and World Health Organization have been warning consumers about for years, stating that nobody should consume deer meat with a known prion disease.
Since 2002, testing for CWD in the deer population has been ongoing. According to the Wisconsin Department of Natural Resources (DNR), 25 of Wisconsin’s 72 counties have detected CWD in their wild deer herd. The majority of the disease is concentrated in the southern farmland area of Wisconsin and the annual CWD detections show that the disease is geographically spreading (figure 4). With CWD killing more deer each year and research funds drying up, the hope of stopping the spread is diminishing.
Exactly how CWD is spread is not entirely known. Scientists think CWD prions spread between animals through feces, saliva, blood, or urine. This happens either through direct contact or indirectly through soil, food or water contamination. They think that if an infected deer dies, the CWD prions absorb into the soil and stay there for a long time. Then they wait in ambush for another deer to feed in the area. This includes when a hunter kills a deer in one county, heads home to another county to butcher the deer and discards the bones in the woods.
Deer are also very social animals. They often feed in groups and groom each other. In the fall, they urinate in common locations to signal their presence. Artificial feeding like salt licks are another potential situation that increases the likelihood of both direct and indirect transmission.
To address these issues, state wildlife agencies have imposed strict regulations against transporting a hunter-harvested deer out of a known CWD area. Other regulations prohibit baiting, artificial feeding, and putting out salt or molasses licks. Such actions are common among hunters to attract deer to their hunting area or even to get photos on a trail camera for pre-season scouting. Granted, researchers don’t fully understand the means by which CWD spreads. Nevertheless, such precautions are needed to deter spreading and preserve the deer population.
Wisconsin hunters were familiar with CWD because of hunting in other states. According to the Chronic Wasting Disease Alliance, CWD was first identified in the 1960s as a clinical disease in captive mule deer at a wildlife research facility in Colorado. To Wisconsinites, CWD was once thought of as a Western states problem. Then, things became surreal when CWD was found on a Wisconsin captive deer farm.
Shortly after that discovery, wild deer in the surrounding area began testing positive for CWD. Suddenly, CWD launched to new heights of concern. In a panicked reaction, Wisconsin mobilized a battle plan to stop CWD. It was a sad and disturbing time for hunters. The DNR established a 287-square-mile eradication zone centered over the area where the initial positive tests had come from. The mantra became, “If it’s brown, it’s down.” Landowners near the eradication zone where given special permits to shoot deer throughout the year to contain the disease.
At the time, Darrell Bazzell, secretary of the Department of Natural Resources, said, “If we want to have healthy deer and deer hunting in the future, we’re going to have to do some hard things now–open our lands and start the very sad task of drastically reducing deer numbers in the CWD zone.” Not fully understanding the disease, the eradication seemed appropriate, but this did not make the process any easier to a responsible and caring hunter. Knowing much of the meat would go unconsumed, conservationist’s hearts were heavy with so much life being wasted away.
Deer farms are probably a major contributor to the spread of CWD. Like most animal farming, business includes the purchase, sale, and transport of farm animals across states lines and sometimes country borders. Prior to the CWD epidemic, people transported potentially infected deer to other deer farms throughout America. The regulations governing commercial deer operations varies from state to state. Some states have banned the movement of captive deer coming from another state. Some states have even implemented aggressive rules requiring the killing of all captive deer when a member of the herd tests positive on the farm.
Concern over CWD management is not a one-way street. Hunters and conservationists generally support Wisconsin’s plans to thwart CWD, but on the other hand, deer farmers are more concerned with their livelihood. Earlier this year, Wisconsin Governor Scott Walker called on the state to be more aggressive in its response to the spread of CWD. Kremer reported that Wisconsin deer farmers and hunting ranch owners fear they will be driven out of business because of Walker’s CWD plan.
Some of these hunting ranches can cost as much as $10,000 to hunt there due to the chances of bagging a trophy. Walker’s proposal includes enhanced fencing and the mandated kill of an entire deer farm with an infected herd. The plan also includes the movement of live deer from farms in CWD positive counties. Walker explains, “We need to protect Wisconsin’s hunting traditions and long-standing heritage by working together to contain the spread of chronic wasting disease in deer.”
Whitetails of Wisconsin, a group that represents Wisconsin’s deer farms, was quick to criticize Walker’s plan. They stated that Wisconsin has already wasted millions on bad strategies to fight CWD. In turn, the group diverted blame of CWD away from deer farmers and claimed that it is more likely due to hunters irresponsibly moving and disposing of carcasses. Regardless of the management strategy, curbing CWD still has a long way to go with gaining support and cooperation. After all, no one wants their hunting abilities or business to be affected.
Wisconsin has 16 years of Chronic Wasting Disease management experience at this point and one thing has become clear: controlling CWD in the wild deer population will continue to be extremely challenging. The DNR developed the Chronic Wasting Disease Response Plan: 2010 – 2025 as a long-term plan to limit the spread of CWD. So far, the longest standing solution has been to kill a lot of deer. However, evidence has not shown that eradication is slowing CWD’s spread in deer. The plan has a number of management and monitoring actions to reach the DNR’s goal. These actions include, additional hunting permits, increase access to CWD testing sites (figure 5), ban on feeding and baiting deer, regulating and testing of deer farms, and cooperating with the Department of Health Services to maintain a registry of persons known to have consumed CWD positive venison.
Management of the disease is controversial particularly because significant population reduction is involved. Thus, the DNR has incentivized hunters by paying meat processors to store meat until test results arrive. Then, the parties involved donate meat found to be CWD free to food pantries. Conservationists feel better knowing that meat is not being wasted. The DNR makes it clear in their plan that they believe population reduction is the most effective disease control method.
Managing Chronic Wasting Disease is very challenging. Results may take years to measure because CWD is such a slowly progressing disease. Another challenge is the involvement of deer hunters and landowners. Not every hunter is supportive of the DNR’s plan so they may not participate in the culling of additional deer. Plus, landowners may not be fond of opening up their land for strangers to hunt on. This is one of the areas that the DNR is exploring their options to work cooperatively with landowners and hunters.
A potential solution using a vaccine may be within our grasp. Researchers at the Center for Cognitive Neurology have developed a vaccination to protect deer from CWD. The vaccine could be the beginning of treating other prion based disease as well. The researchers think they need only a 10 percent inoculation to induce herd immunity. Scientists conducted vaccination experiments on five deer. They exposed all of the deer to CWD prions and housed them together to keep them in constant exposure. Four of the deer given the vaccine took much longer than a separate control group to become infected, and the fifth deer remains CWD free.
Vaccines, wildlife management strategies, and research all require lots of money. Not having funds makes developing new tools very difficult. More money could be on the way, though. Wisconsin representatives, Ron Kind and James Sensenbrenner introduced H.R.4454 – the Chronic Wasting Disease Management Act in November 2017. If passed, the bill would provide $35 million to conduct CWD research and management.
Wherever Chronic Wasting Disease exists, there is a potential for serious negative impacts on the future of deer and hunting traditions. With increasing positive tests and additional geographic areas of disease occurrence, it seems that CWD will continue to spread. CWD researchers are still dealing with many unknowns. How this will impact deer in the long-term is uncertain. Even though management success is difficult to monitor, efforts must continue using the best available information. As new science is developed and our understanding of CWD expands, management strategies must be modified. One of the biggest contributors to successfully managing CWD will certainly be state and federal funding.
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Bryce Vieth lives in Colorado Springs. After a career with Army Special Forces, he now spends his free time climbing 14ers, camping, and bowhunting. He recently started a woodworking LLC to experiment with entrepreneurship and a goal of opening more businesses in the future. He is pursuing a B.S. in Mechanical Engineering at UCCS.
