Early detection and intervention are key when it comes to minimizing the spread of chronic wasting disease in deer, and there are many ways wildlife agencies do this, including targeted removal. Targeted removal is a precision removal of deer in locations where CWD was detected previously. Landowner approval is required, and sometimes landowners can assist in the effort. Goals include removing additional infected deer in that location as soon as possible, determining the prevalence rate, and reducing deer density to slow deer-to-deer spread. Often misunderstood, targeted removal is one of the most effective ways to hold prevalence rates low and buy time until better CWD solutions are found.
Many agencies use targeted removal as part of their CWD management toolbox, and there are ample data to support the effectiveness of this strategy. At a recent CWD meeting in Jefferson City, Missouri Department of Conservation (MDC) Director Jason Sumners presented a chart that demonstrates states using this method are holding CWD rates relatively low, while states that don’t use it are not. Seen above, the chart is based on this scientific study.
The Missouri Example
Speaking of Missouri, MDC has done a tremendous job fighting CWD since it’s initial detection in the Show-Me State’s wild deer population 13 years ago. Targeted removal efforts were implemented almost immediately, and they haven’t stopped. Combined with mandatory sampling in some cases, voluntary sampling, and a variety of other collection techniques, prevalence rates have remained below 1% statewide, and in all but one positive county remains under 3%.
A common misconception is that targeted removal is a localized eradication of deer populations that will leave hunters with less opportunities to fill their tags. In fact, targeted removal in Missouri has accounted for less than 1% of the total deer harvest since targeted removal began, and Missouri hunters actually harvested more deer, and more bucks, in recent seasons than they did before the discovery of CWD in the state.
CWD Intervention must start early and continue in order to slow the spread, and because Missouri has done just that, productive deer populations and sustainable hunter harvest are ensured for the long haul. But let’s not forget the second half of Jason’s message: states that don’t use targeted removal are not holding CWD prevalence rates low.
CWD in Wisconsin
For example, Wisconsin began using targeted removal shortly after finding the first positive case in 2002, which kept prevalence rates low at first. It is now known that targeted removal is most effective when efforts are focused close to known CWD detections, rather than on a widespread scale, and early on the Wisconsin DNR took the latter approach. This led to strong opposition from hunters, landowners and the public who were skeptical of the technique itself. Political pressure ultimately resulted in stopping the practice in 2007. Since then, prevalence rates have climbed steadily to over 10% across management zones, with some areas exceeding 50%! It can be extremely difficult for hunters to find the motivation to harvest enough does if you know that half of the population in your area may have CWD, and decreasing doe harvest further contributes to the spread.
CWD in Alberta
Further north, Alberta also ceased targeted removal efforts after just three years, resulting in another drastic spike in prevalence across management zones. Infection rates now approach 27% in mule deer and nearly 9% in whitetails. Mule deer and whitetail bucks tend to be 1.5 to 3 times more likely to be infected with CWD compared to females, and because of that, Alberta is seeing prevalence rates of 32.5% in mule deer bucks and 11% in whitetail bucks. If you factor in elk and moose, overall prevalence for all cervids across Alberta is over 16%.
CWD in Illinois
Illinois is another prime example of using targeted removal to keep prevalence rates low. First discovered in Boone County in 2002, targeted removal was implemented in 2003 as part of their targeted surveillance program. As a result, overall prevalence rates have remained below 3% until recent years, with latest estimates around 9.2% for adult deer of both sexes in the known CWD area. According to the Illinois DNR, these spikes are clearly indicative of shifting disease dynamics, and notably the continual accumulation of prions in the environment and increasing probabilities of infection of free-ranging deer across northern Illinois. While management has been successful overall, new updates to the CWD surveillance and management program has ceased targeted removal efforts in high-prevalence areas (>5%) as of January 2025. This is a slippery slope when we look at what has happened to other states who abandon this surgical strike.
Take Action Against CWD
Doing nothing means CWD will get worse, and targeted removal works. It is not a one-size-fits-all approach, and it cannot eliminate CWD, but it is an effective tool that wildlife agencies can employ. As hunters it is our responsibility to assist through voluntary sampling, education and increased doe harvest to ensure the future of wild deer, wildlife habitat and hunting.