Study shows sharpshooting can control CWD

February 12, 2016

Beckie Joki Outdoors Writer

While there are many unknowns about Chronic Wasting Disease (CWD), several studies have been done that may shed some light on which control efforts seem to be most effective. CWD was found in Illinois and Wisconsin at approximately the same time. In 2002, there was a scramble to try to control an outbreak of the disease in both states. Both states implemented a ban on baiting and feeding deer located in areas where the disease had been detected. The translocation of deer was also banned. Sharpshooting was seen as a viable control measure in both states as well. However, in 2007, largely due to negative feedback from the public, sharpshooting was eliminated as a control measure in the state of Wisconsin. In Illinois, however, the specific, targeted sharpshooting continued. In a study called “The importance of localized culling in stabilizing chronic wasting disease prevalence in white tailed deer,” Mary Beth Manjerovic, Michelle L. Green, Nohra Matews-Pinilla, and Jan Novakofski looked into the differences in CWD prevalence in deer herds in southern Wisconsin and northern Illinois from 2002 to 2012. The researchers were from the Illinois Natural History Survey – University of Illinois Urbana-Champaign and the Department of Animal Science – University of Illinois Urbana-Champaign. While culling of game species by government agencies is one means of disease control, it can be met with some resistance from the public, they said. That was the case in Wisconsin. Beginning in 2007, the state decided to use only traditional public hunting as a means of control, while Illinois continued using sharpshooters to target specific areas and parts of their herd. Once CWD is established in a herd, it is nearly impossible to eradicate the disease from that herd. It was hoped, however, that through targeted culling, the state of Illinois would be able to control the spread of CWD. According to the study, the Illinois Department of Natural Resources “implemented a disease management program to bring about small scale population reductions in known CWD infected areas by incorporating additional hunting seasons and government culling.” Included in the study was a graphical depiction of the prevalence of CWD in both states from 2002 to 2012. The graph shows that when both states were involved in localized culling, the prevalence of CWD (calculated as the number of positive deer divided by the number of deer tested annually) remained relatively flat at around 1 percent. However, the study shows things changed in 2007 when Wisconsin did away with government culling and instead relied on increased hunting to help control the disease. Starting in 2007, the prevalence of CWD in the Wisconsin herd started to increase sharply. In 2012, the prevalence was near 5 percent and still climbing. The researchers then looked at the effects government culling had on hunting harvests in the CWD-infected area. The Illinois culling program, according to the study, removed an estimated 747 deer from 10 counties where CWD had been detected since 2002, using the Illinois DNR’s numbers. They said that number represented approximately 4.9 percent of the deer removed from those counties during each hunting season. They also stated that the government culling “has not resulted in a reduction in overall hunter harvest in those counties.” In total, when comparing the 10 years during which the government was culling deer to the 10-year period before use of this CWD management tactic, “significantly more deer” were harvested by hunters in those 10 counties. The average annual harvest, they said, increased by just over 18 percent. In only two counties were the harvest numbers reduced. The harvest in Boone County was reportedly reduced by 20.1 percent and McHenry County by 11.2 percent. Overall, however, the numbers were up, which may have helped give most hunters more confidence in the culling program. Illinois, the study said, felt that relying only on hunter harvest was a less effective way of controlling CWD. Normal hunting, they said, does not tend to concentrate efforts in specific areas with a high risk of CWD. Government culling, however, can be concentrated, thereby keeping CWD prevalence in check without lost hunting opportunities for the general public. The study mentioned that other variables that have an effect on the prevalence of CWD had not changed in the areas of either state that were involved in the study. The main variable, it was said, was the management philosophies imparted by both states. Other environmental factors that have an effect on CWD transmission, such as clay content in the soil and forest cover, did not change over the period of the study, the researchers added. According to the study, there are costs, both in controlling a wildlife disease and in allowing the disease to run its course. While the study did not address the issue specifically, it stated that it was likely that those costs played a role in state agency management decisions. Public opinion can also influence funding for projects and play a role in management decisions, according to the study. Government culling, the researchers concluded, has likely “achieved the goal of preventing an increase in CWD without a consistent reduction in hunter opportunity” throughout the state. Beckie Joki may be reached at

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