Diseased Deer
Spread of Chronic Wasting Disease in Illinois and Wisconsin
An incurable prion disease that infects thousands of deer and may be a threat to humans continues to spread despite human intervention.
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What is Chronic Wasting Disease?
Chronic Wasting Disease (CWD) is a prion disease (like bovine spongiform encephalopathy (BSE) AKA mad cow disease) that can infect cervids (deer-like animals).
It was first identified in 1967 in captive mule deer at the Colorado Division of Wildlife Foothills Wildlife Research Facility in Fort Collins, Colorado. It is currently incurable and results in the death of the animal.
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The Spread
For around 30 years, CWD was only found in Colorado and neighboring Wyoming. Around 2000, CWD was first found outside of this region and begin spreading rapidly.
In 2002, CWD was found in southern Wisconsin and in northern Illinois. Both states' Department of Natural Resources immediately began working to contain the outbreaks.
What's the big deal with CWD?
Potential spread vectors for CWD in deer
Prion diseases like CWD are very easily spread and extremely hard to destroy. The misshapen proteins are extremely small and difficult to destroy, including by cooking. There is currently no proof that it can cause disease in humans; however other prion diseases have.
In the 1990’s the United Kingdom experienced an outbreak of BSE. The outbreak of mad cow disease peaked in the U.K. in 1993, with about 1,000 cases every week. By the end of 2015, the U.K. had recorded more than 184,500 cases.
What to do in the Midwest?
Graph of the percentage of CWD tests which were positive during a given year for Illinois and Wisconsin from 2003-2013.
Initially the response was very similar in both Illinois and Wisconsin. Both states used as many control options as possible, including increasing the number of hunting licenses and providing widespread testing of harvested deer. CWD management is generally popular though some methods are more disliked by hunters than others.
This includes the use of sharpshooters to kill deer suspected of being infected by CWD. Sharpshooting is disfavored by hunters as it both decreases the density of deer in an area, making it harder to hunt, and uses bait to gather deer, which has been banned for hunters in areas with CWD in both states. This discontent among hunters began to grow in both states.
Diverging Strategies
Wisconsin | Illinois |
|---|---|
In 2007, growing discontent bubbles over and results in the de-funding of the sharp shooting program in Wisconsin. To compensate, the state doubles down on the hunter focused efforts like giving specific CWD tags for very cheap and replacing all tags used on deer with CWD for free. | Across the border in Illinois, the DNR continues with sharpshooting efforts, despite hunter push back. |
Since the shift…
Since the change in strategy, CWD spread has accelerated in Wisconsin with higher prevalence of CWD and many more counties affected.
In Illinois, CWD has spread to some new locations within the state, but the spread has been slow and the prevalence of the disease in a given area has remained low.
CWD in Illinois and Wisconsin
What is happening now?
Graph of the percentage of CWD tests which were positive during a given year for Illinois and Wisconsin from 2003-2023.
Illinois has maintained their management practices and funding leading to limited further spread. While still extremely hard to control, the disease has taken a longer time to move to new areas and prevalence of CWD is still low.
Wisconsin has not return to sharpshooting and the disease has continue to spread further north, to almost all counties. Wisconsin has accepted the reality of CWD in the state and there are now pushes to remove further protections against the spread of CWD, like the ban on baiting deer for hunting.
What else can be done?
Form for a CWD test from the Wisconsin DNR
The spread of CWD seems impossible to completely halt. While Illinois has massively slowed the advance, Wisconsin, hunters have become more comfortable with CWD and hunting has not seen a CWD driven drop off.
There is active work to make testing for CWD faster and development of a test that a hunter could administer themself, to increase testing before eating.
CWD range as of 2023
There have been no strategies successful in truly stopping the spread of the disease across the country and the world. Today, there are still no known human health consequences of CWD.
While both of those remain true, in the long term we may need to look to states like Wisconsin to understand how to best live with the disease when it no longer can be controlled.
