Chronic Wasting Disease Update

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Whitetail Deer
When CWD was first discovered in Wisconsin, sharpshooters culled hundreds of white-tailed deer to determine the disease’s prevalence..

What about deer hunters’ promises to increase the antlerless deer kill without EAB? With EAB, deer hunters in CWD zones generate a 1-to-2.8 buck-to-antlerless kill ratio, but only a 1-to-1.2 ratio with either-sex regulations. “Most people only want to shoot one deer, so unless they’re required to shoot an antlerless deer first, many of them pass until they see a buck they want,” Bates said. “Then they shoot and go home.”

DNR data support Bates’ comment. Even with 53 of Wisconsin’s 130 deer management units under EAB regulations in 2008, 65 percent of successful hunters statewide shot only one deer, 24 percent shot two, 7.26 percent shot three and only 2.4 percent shot four.

Bates also opposed the DNR compromise in 2008 that eliminated all gun-hunting before the traditional nine-day November season, except for a four-day antlerless-only season in mid-October.

“When we had those long gun seasons starting in mid-October, we had two years when 53 percent and 58 percent of the deer harvested fell before the regular gun season opened,” he said. “Gun-hunts during the rut helped push the herd closer to where it needs to be. There’s a disconnect there. Folks tell us they want to see more deer, but then they demand no gun-hunting during the rut when they’d see more deer.

“That’s one of deer hunting’s biggest dilemmas,” Bates continued. “Lowering deer numbers goes against what average deer hunters want. They don’t want to shoot more deer; they want to see more deer. But to get a handle on CWD, our policies have been totally opposite of that. They have to shoot more and see less. People don’t want to do that. As a result, we’re no longer effectively reducing the herd. And where we have CWD, it’s getting worse.”

No-Confidence Votes

Such disagreements reached the next level in August 2009 when the DNR’s seven-citizen Natural Resources Board – which sets agency policy -- voted 7-0 to table the agency’s long-awaited CWD management plan. Rather than approve the five-year strategic plan -- which was two years in the making -- the Board set it aside for further review by a scientific panel.

In delivering the initial “no-confidence” vote, Board members said the plan would merely monitor CWD, not control it. The Board wasn’t alone in its rebuke. Several independent scientific reviewers shared their concerns before the Board’s vote. Here’s a sampling:

“The plan appears to overly bend to politics and deer hunter preferences rather than aggressively striving to implement all possible deer management practices to keep the disease in check. … It is our feeling that many vocal hunters, deer lovers and their elected officials want it both ways; i.e., a large deer population and traditional hunting seasons/practices, and effective control and containment of CWD in Wisconsin. (We believe) it is not possible to have it both ways.”
– Dr. Doug Kratt, DVM, Wisconsin Veterinary Medical Association

“It is my opinion that the stated goal of 19 deer per square mile (of range) is too high to have an impact on CWD dynamics. This deer density is not unlike that found in much of northern Illinois’ CWD area prior to intervention, and CWD did not appear to be constrained under those conditions. (Another) aspect of the plan that’s discouraging is the lack of acknowledgment that the success/failure of CWD in either Wisconsin or Illinois has ramifications that cannot be overcome in the other state.”
– Paul Shelton, Manager, Forest Wildlife Program, Illinois DNR

“(According to the plan,) the new goal for the entire CWD management zone is 88,000 deer, approximately 20 deer per square mile of deer habitat. … The deer population (for this area) was below 100,000 animals in the late 1980s. … It is very likely CWD was present in Wisconsin at that time. If that is the case, CWD was able to persist at that population density. … It is unclear how the agency can suggest to its constituents, or itself believe, that CWD will be impacted by population reduction to this level.”
– Bryan J. Richards, CWD Project Leader, U.S. Geological Survey, National Wildlife Health Center

Wisconsin’s Natural Resources Board eventually signed off on a revised plan several months later, but suggested it still had more to do with politics than science.

Worsening Trends

How could the Wisconsin DNR be so vulnerable to these blunt critiques after dealing with CWD more than seven years? It’s not as if the agency ignored the disease. The DNR has worked with several state agencies and universities on more than 30 CWD-related studies, and spent nearly $41 million on research, disease-monitoring, sharpshooting, registration/sampling stations between 2002 and 2009.

And it’s not as if CWD is disappearing. As of Oct. 26, 2009, Wisconsin lab technicians had checked 104,320 whitetails in the disease-management zone and found CWD in 1,177 deer, a 1.13 percent overall infection rate. They also tested 47,771 deer outside the CWD zone, none of which tested positive.

Unfortunately, CWD-infected deer come largely from the disease’s 210-square-mile core area near the town of Mount Horeb west of Madison. Further, the disease rate jumped unexpectedly there in 2008 for bucks and does of all ages, with the biggest increase occurring in older bucks. The infection rate for bucks 2.5 years and older surpassed 15 percent in 2008 after hovering around 10 percent since 2002. The infection rate for bucks in this age group then hit 22 percent in 2010. The infection rate for 1.5-year-old bucks jumped to 6 percent in 2008 after sitting near 3 percent since 2002, and then neared 9 percent in 2010.

In females, the disease rate for 18-month-old does hit 5.25 percent in 2008, up from 3.25 percent in 2007 and the fifth straight year the disease increased for this group. It then neared 7 percent in 2009 before registering about 2 percent in 2010, likely an anomaly. The infection rate for does 2.5 years and older hit 6.5 percent in 2008, up from about 5 percent in 2006 and 2007, nearly a point higher than the previous high, 5.75 percent in 2005. It then approached 8 percent in 2010.

Davin Lopez, the Wisconsin DNR’s CWD project leader, said the core area’s increases are impossible to explain away. “Maybe there’s factors we’re not yet realizing,” Lopez said, but by the same token, that prevalence rate for adult males is huge. This could be our scientific sign of the dramatic increase in prevalence other states have documented for CWD. The disease has shown exponential rates of increase once it starts growing.”



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