Photo by: NPS / Jacob W. Frank
What is Chronic Wasting Disease?
Chronic Wasting Disease (CWD) is a deadly neurological disease that affects hooved mammals such as deer, elk, and moose— species that are crucial to North American ecosystems. CWD can spread directly from animal to animal and indirectly through the environment, meaning animals can contract it from soil, water, and food. Despite being first detected in 1967, much remains unknown about CWD. This disease is caused by prions, abnormal proteins that damage the brain and lymphatic system. Once an animal is affected by CWD, it may live for a few years, but the disease will kill it. Prions can linger in the environment for two or more years, potentially infecting other animals. At present, there is no effective vaccine for CWD.
As Chronic Wasting Disease continues to spread across North America, it is crucial to implement effective management strategies. Many government agencies are exploring expensive techniques to limit the spread; However, a natural “deterrent” of CWD already exists. Researchers have proven that wolves limit the spread of CWD at a rate that could help prevent transmission (Wild, 2011). The remarkable thing about wolves is that they already naturally exist in many areas where officials have detected CWD.
Figure 1: CWD Map
How Can Wolves Help?
Wolves are selective predators, meaning they tend to prey on injured and diseased animals, including those with chronic wasting disease. A study indicates that selective predators, like wolves, are much more likely to kill CWD-infected deer than hunters (Krumm, 2009).
A model predicted that “CWD prevalence could be halved within a decade and eliminated within the century if a pack of wolves consistently and selectively removed 15% of deer in a closed population” (Waldner, 2016).
Another benefit of wolves is that they cannot be infected by CWD. This means that when wolves consume infected animals, they consume the prions without increasing the infection rate. Although their feces still carry the infected prions, research suggests that these prions may begin to break down in a predator’s digestive tract, aiding in their removal. The most important thing wolves do is remove infected species that directly affect one another, which is crucial for elk and some deer that live in herds where direct infection could be high. Effective removal of infected animals from herds may decrease the transmission rate and increase the survival of deer, elk, and other CWD-susceptible species.
By affecting their prey’s behavior, wolves may indirectly affect the spread of CWD. Some studies suggest that the presence of wolves changes the behavior of deer and elk in a way that reduces their likelihood of becoming infected with CWD through indirect environmental exposure (Waldner, 2016).
What are the implications?
For wolves to play an effective role in reducing Chronic Wasting Disease (CWD), there needs to be a stable wolf population. Many western states where CWD and wolves are present have passed anti-wolf legislation.
In Wyoming, “74% of buck mule deer killed by hunters are in the process of dying anyway from CWD” (Koshmrl, 2024).
Wolves could help decrease this number. Instead of promoting a healthy wolf population, Wyoming has classified wolves as ‘predatory animals,’ allowing them to be killed without a license at any time of the year.
In states like Idaho, where CWD has not been widely detected, wolves could play a crucial role in limiting the spread. However, Idaho has implemented some of the harshest wolf legislation yet. Senate Bill 1211 permits a reduction to 150 wolves, which is about a 90% reduction of Idaho’s wolf population.
Rather than treating wolves as enemies, we should work with them to mitigate CWD transmission.
Photo by: Karen Crewe from Wildlife Photo of the Day.
The Wood River Wolf Project uses non-lethal deterrents to minimize conflicts between wolves and livestock. This project promotes coexistence between wolves and ranchers and has been proven effective during its 16 years of operation. It serves as a model for coexistence, contributing to the maintenance of a healthy wolf population and assisting in the reduction of CWD spread.
References
- CDC (2024, May 13). Chronic Wasting Disease in Animals. https://www.cdc.gov/chronic-wasting/animals/index.html#:~:text=Scientists%20think%20CWD%20spreads%20between,soil%2C%20drinking%20water%20or%20food
- Center for Human-Carnivore Coexistence (2020, May). Wolves and Disease. Extension. https://extension.colostate.edu/topic-areas/people-predators/wolves-and-disease-8-006/
- Koshmrl, M. (2024, June 24). A Wyoming mule deer herd is so riddled with CWD it could nearly vanish. https://wyofile.com/a-wyoming-mule-deer-herd-is-so-riddled-with-cwd-it-could-nearly-vanish/
- Krumm, C. E., Conner, M. M., Hobbs, T. N., Hunter, D. O., & Miller, M. W. (2009). Mountain lions prey selectively on prion-infected mule deer. The Royal Society. https://doi.org/10.1098/rsbl.2009.0742
- National Wildlife Health Center (2024, June 8). Distribution of Chronic Wasting Disease in North America. https://www.usgs.gov/media/images/distribution-chronic-wasting-disease-north-america-0
- USDA (2023, December 18). NWRC Spotlight: Accomplishments in Chronic Wasting Disease Research. Animal and Plant Health Inspection Service. https://www.aphis.usda.gov/about/news-and-media/aphis-action/nwrc-spotlight-accomplishments-chronic-wasting-disease-research#:~:text=CWD%20is%20caused%20by%20abnormal,%E2%80%9Cwasting-away%E2%80%9D%20death
- Waldner, C. L., Bollinger, T. K., Johnston, A. C., & Uehlinger, F. D. (2016). Systematic review of management strategies to control chronic wasting disease in wild deer populations in North America. National Library of Medicine. (2)
- Wild, M. A., Hobbs, T. N., Graham , M. S., & Miller, M. W. (2011). THE ROLE OF PREDATION IN DISEASE CONTROL: A COMPARISON OF SELECTIVE AND NONSELECTIVE REMOVAL ON PRION DISEASE DYNAMICS IN DEER. Journal Of Wildlife Diseases. https://doi.org/10.7589/0090-3558-47.1.78
- Williams, E. S., & Fischer, J. R. (2002). CWD Overview. Cwd-Info.org. https://cwd-info.org/cwd-overview/
- (n.d.). Wood River Wolf Project. https://www.woodriverwolfproject.org/
- Wyoming Game and Fish Department (n.d.). Wolves in Wyoming. https://wgfd.wyo.gov/wyoming-wildlife/large-carnivore/wolves-wyoming#:~:text=Wolves%20outside%20the%20WTGMA%20are,year-round%20without%20a%20license
