From left, Brian Frerk, Josh Frerk, Ben Zill, Bob Bins and Jim Zill meet up in a field while deer hunting on private property in Kewaunee County in November. The Wisconsin Department of Natural Resources has sought the assistance of hunters in controlling the spread of chronic wasting disease. / Evan Siegle/Gannett Wisconsin Media
A Wisconsin deer that tested positive for chronic wasting disease. / Photo supplied by the DNR
CHRONIC WASTING DISEASE 101
CHRONIC WASTING DISEASE is a neurological disease similar to mad cow disease in cattle and scrapie in sheep, but it affects white-tailed deer, mule deer, moose and elk. It is caused when a naturally occurring protein mutates into an infectious, misfolded form — called a prion — and begins accumulating in nervous and lymphoid tissues, according to the Wisconsin Department of Natural Resources.
CWD was FIRST DISCOVERED IN WISCONSIN IN 2002, though officials believe it was introduced at least 20 years ago in two separate locations – near the border of Dane and Iowa counties and in southeastern Rock County. MORE THAN 1,500 DEER HAVE TESTED POSITIVE for CWD in Wisconsin since 2002, including a high of 218 in 2010.
The disease is SPREAD THROUGH DIRECT CONTACT with infected deer or CWD-contaminated soil, and the disease can linger for at least three years in soil.
An infected deer will show no immediate symptoms as the disease incubates for at least 17 months before outward signs begin to appear and the clinical progression begins, research shows. Outward signs typically last between several weeks and several months before death. They include emaciation, widened stance, lowered head, excessive salivation and behavioral changes such as walking a repetitive course.
THERE IS NO VACCINE and no signs deer can become immune to the disease.
The U.S. Centers for Disease Control and Prevention says there is “NO STRONG EVIDENCE” THAT CWD CAN BE TRANSMITTED TO HUMANS, but it advises against eating infected animals. The CDC says many years of follow-up are needed to be able to say with certainty whether CDC poses a risk to humans.
Tediously slow but invariably lethal, chronic wasting disease is the most significant threat ever to face Wisconsin’s whitetail deer population and its hunting culture, wildlife officials say.
But tell that to a hunter and you likely will see an eye roll or hear criticism of the Wisconsin Department of Natural Resources’ CWD management efforts.
“I don’t think CWD is enough of a threat to do what they’re doing to the deer herd and to the state’s hunting,” said Andy Townsend, 24, of Milton, who shot and later ate a CWD-positive buck in January.
“I’m friends with 100 guys, and 99 percent think this is getting kind of absurd and they should just let (CWD) run its course.”
Extensive studies so far have yielded no evidence of human health risks from CWD. Questions remain about its potential impact on the age and size of the state’s deer herd.
“Prevalence and distribution continue to slowly grow,” said Davin Lopez, DNR biologist and CWD team leader. “Ultimately, it could reduce deer numbers to a level that would significantly impact hunting permanently.”
The state’s highest concentration of CWD is in a 210-square-mile section of southern Wisconsin in Dane and Iowa counties, where nearly 12 percent of all deer are CWD-positive, according to DNR estimates completed this month. The previous high in that area was 8.4 percent in 2008.
Last year, 219 deer tested positive for CWD, which is 40 more than 2009 and the highest yearly total since the disease was discovered here in 2002, according to the DNR. The previous high was 205, a total reached in both 2002 and 2006.
The DNR has changed CWD management tactics and goals several times since the disease was first discovered in Wisconsin in 2002 — most notably abandoning the initial eradication goal as impossible.
The current effort is aimed at overall population reduction. CWD is spread through direct contact with infected deer or CWD-contaminated soil, so fewer deer means fewer chances for healthy deer to contract the disease.
“We only have maybe 15 to 20 percent prevalence in our adult males (bucks) in very small areas at this point, so it’s not surprising that most people don’t see a sick deer,” Lopez said.
“They’re not seeing a sick deer, they’re not thinking it’s really a problem.”
Despite nine years of extended hunting seasons, the deer population fell only slightly in the 9,000-square-mile area that covers the southern quarter of the state — called the CWD management zone.
About 184,000 deer roamed the management zone at the close of the 2010 hunting seasons, down from 198,000 in 2001, according to DNR estimates. The current population goal is 78,000, a number established in 2007 after hunters criticized the initial 49,000 goal as unachievable.
“It’s overpopulated even regardless of CWD,” Lopez said.
Extended hunting seasons in the CWD zone have drawn the ire of hunters and landowners, but the DNR defends the additional opportunities as the best available means to slow the spread of CWD. Mature bucks are most vulnerable to CWD, but Lopez said lowering the number of does is the best way to limit the population.
“Basically we’re asking for herd reduction now that could bounce back in lieu of permanent herd reduction later,” Lopez said.
The DNR has opened two additional gun seasons in the CWD zone. A four-day antlerless hunt is held in mid-October and a two-week gun season runs from late December to early January began in 2008.
The DNR also issues an unlimited number of tags in the 22 management units that comprise the CWD zone, but that is subject to earn-a-buck requirements.
Terry Frey, who co-founded a landowner group to advocate limiting hunting to the traditional nine-day season, said landowners in the CWD zone are frustrated with what he calls “endless seasons.”
“It’s here, we’re not going to eradicate it,” the 56-year-old Black Earth resident said of CWD. “How long can these deer seasons go on where people can’t go out and enjoy their property?”
Most of the 15 states with CWD in wild populations have built their management plan around some kind of population control. Methods include allowing sharp shooting, extending seasons to issuing additional licenses in key areas.
But the state with the most CWD experience — Colorado, where the disease was first discovered in the wild in 1981 — has abandoned population control efforts.
Battling CWD in deer, mule deer, moose and elk, Colorado set out in the early 2000s to reduce its deer herd in core areas by half, said Jeff Ver Steeg, assistant director for wildlife programs with the Colorado DNR. Officials dropped that goal after several years — calling it unattainable — and soon after abandoned sharp shooting and issuing extra licenses.
“(Population reduction) just didn’t really seem to make that big of a difference, and prevalence was not something that was increasing at a huge rate either, especially in hunted populations with enough turnover,” Ver Steeg said. “We’re back to managing for herd objectives and recreation. CWD is not the primary driver in terms of our management objectives.”
Unmanaged in Wisconsin, CWD would slowly spread to the rest of the state while infecting an increasing percentage of the herd — potentially up to 40 percent of adult male deer, Lopez said.
Wyoming has reached that prevalence level in areas covering thousands of square miles, Lopez said. Wyoming is the only CWD state that monitors but does not actively manage the disease.
“This is a very slow-progressing disease, and the population level effects that would affect hunting or deer numbers at all aren’t going to be seen for … decades if not longer in Wisconsin,” Lopez said.
Said Ver Steeg: “I think it’s fair to say the jury’s still out. We just don’t have enough long-term data to answer that question.”
Success in outreach
Lopez said lack of support from hunters is the single biggest problem facing the state’s CWD management. The DNR needs hunters to harvest more deer in the CWD zone and landowners to allow more access to hunters, he said.
“We ultimately have to work together if we’re going to be reasonably successful doing disease management,” he said.
A 2006 Legislative Audit Bureau analysis of the CWD program said it was “imperative” for the DNR to improve communication with hunters, calling it unlikely that the disease could be controlled without public support.
But telephone surveys done for the DNR last summer show only 7 percent of hunters who recently hunted in the CWD zone believe the disease is currently a “serious” problem. Only 15 percent believe it will become serious if left untreated.
The DNR’s goal on the disease is also unclear to many, with 60 percent of landowners and hunters in the CWD zone saying they believe the DNR is attempting to eradicate the disease.
Eric Litke writes for the Sheboygan Press.