Study: Deer culling has kept CWD controlled
Lee Creek, Ill. — Despite objections by many hunters and most wildlife watchers, the state’s deer culling program appears to be accomplishing its goal of containing and limiting the spread of chronic wasting disease.
This suggestion comes from a new report out of the University of Illinois, where researchers spent time and effort looking at the effectiveness of sharpshooting deer.
“[Culling] is a textbook scientific strategy for control,” Jan Novakofski, a professor of animal sciences at the U of I and one of the authors of a study on culling’s effectiveness, said. Novakofski also happens to be a hunter himself.
“You reduce contact and you reduce the spread of infection with the smallest overall impact on healthy deer,” he added.
The study, which appears in the journal Preventive Veterinary Medicine, was conducted under the Illinois Natural History Survey. Findings point out that prevalence of CWD in tested deer remained at about 1 percent from 2002-12 in the state.
The team also found that, although hunters in counties subject to culling programs have claimed a steep decline in the deer population, hunters were actually harvesting more deer each year in each region – regardless of CWD and CWD management.
Culling has not been popular with people who live near forest preserves or wildlife areas where large numbers of deer live. And hunters in CWD counties have campaigned to be allowed to thin the deer herd themselves, instead of hired sharpshooters.
But hunters tend to be too selective when hunting deer – a trait that is beneficial for the hunter but counter to the goal of a culling program, the research team agreed.
CWD made its grand entrance in the state in November of 2002, when a doe in northwest Boone County was diagnosed after demonstrating signs of aspiration pneumonia and behavioral abnormalities.
As of the summer of 2013, DNR has recorded 372 positive cases of CWD in 10 counties. A full 90 percent of infected deer were found in four original CWD counties – Winnebago, Boone, McHenry and DeKalb. Winnebago and Boone counties accounted for 71 percent of positive cases.
Over the past decade, DNR has tested more than 7,000 deer for CWD infection. Those deer sampled have been killed by hunters, vehicle collisions or as part of culling programs. The culling program works like this: DNR annually conducts aerial surveillance to see where deer congregate and sends in sharpshooters to cull deer at the sites with disease.
“We know a lot about how far deer typically move,” Novakofski said. “If they’re sick, they’re going to spread the disease that far. So if you find a deer that’s sick, you draw that small circle and you shoot there.”
Nohra Mateus-Pinilla, a wildlife veterinary epidemiologist at INHS who led the study, said the research team was primarily trying to figure out if Illinois hunters have fewer deer to hunt today than they did before CWD came into the picture. Along with U of I post-doctoral researcher Mary Beth Manjerovic, Mateus-Pinilla maintains that the culling program is working and is having minimal effect on hunting.
“We found that hunter harvest has increased, and the prevalence of CWD has been maintained at low levels for 10 years in Illinois,” Mateus-Pinilla said.
Also compared as part of the study was the Illinois approach and the tactics taken by Wisconsin, which changed its CWD-management strategy from culling to one that primarily allowed hunters to do the job. Wisconsin saw a striking increase of CWD cases in deer after it did that, Mateus-Pinilla noted.
“In the early years in Wisconsin, CWD prevalence was still about 1 percent, just as it was in Illinois,” Manjerovic explained. “Then the strategy changed. Since 2007, CWD prevalence has increased to about 5 percent [in Wisconsin].”
The question Illinois hunters and wildlife fans continue to ask is if killing deer is necessary to test of CWD. Novakofski, who along with Mateus-Pinilla has spent years looking at other animal diseases such as mad cow disease, say “yes.”
“We’ve been looking for 15 years to find a way to detect CWD while a deer is alive, but so far there is no alternative to sampling tissues from a dead deer,” Novakofski said.