Efforts Continue to Contain and Eradicate CWD

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Chronic wasting disease in Wisconsin’s wild deer herd appears to be limited to two areas in the southern part of the state at this time based on current knowledge, say wildlife officials. The officials stress however that CWD remains a statewide issue.

“The importance of deer and deer hunting to Wisconsin is huge,” said Tom Hauge, DNR wildlife management director. “Deer hunting is a $1 billion industry providing countless memorable experiences across generations of families. Although it is easy to think of CWD as southern Wisconsin’s problem, we believe that if we do nothing to actively address this disease now, it will spread and prevalence will increase.

Areas subject to CWD management rules have been modified as more is learned about the disease and disease surveillance better defines the affected area. Maps showing the CWD management zone boundaries, tables with surveillance and testing results and special CWD zone hunting regulations can be found on the DNR Web site.

“As we go into our third fall following the discovery of CWD in the wild herd, I feel we’ve made good progress in dealing with this challenge,” says Hauge. “Two recently completed hunter surveys tell us that a strong majority of hunters agree CWD should be eliminated from the wild herd.

“Landowners and hunters are the key to the success of this effort. We’ve worked hard to keep them informed and stay in close touch with them. A year ago, we shifted away from large public meetings to a system of community liaisons – biologists that visit residents at their homes and farms to update, answer questions, and establish face-to-face contact with affected landowners.”

“We remain committed to eradicating the disease in the known infected areas,” said Al Crossley, biologist in charge of the department’s CWD management effort.

“We are working to limit the spread of the disease from the known infected areas and we’ll continue surveillance to monitor the distribution and prevalence of the disease in the herd.”

Learn and adapt

The department, along with units of the University of Wisconsin, the USGS Cooperative Wildlife Research Unit, the Department of Health and Family Services and the Wisconsin Veterinary Diagnostic Laboratory, is cooperating on 34 CWD research studies in Wisconsin. Another 12 studies are underway in other states. The knowledge gained is being used in Wisconsin’s “learn and adapt” approach to CWD management.

Examples of changing CWD management efforts include modifying the population goal for the disease eradication zone from zero to less than five deer per square mile, and reducing the number of management zones to two: a herd reduction zone (HRZ) with a population goal of 10 deer per square mile, and the disease eradication zone (DEZ).

“This is a long-term effort,” said Hauge. “We’re making progress but we need to keep up the effort. In the first two years of effort, hunters lowered the deer population in deer management unit 70A by 28 percent, from 48 deer per square mile to 35. We need look no further than Michigan and their long-term effort to eradicate bovine tuberculosis from their wild deer herd. During the first seven years of their TB program they reduced the deer population 40 percent and dropped TB prevalence from nearly 5 percent to less than 2 percent - and they are keeping at it.

Surveillance will be concentrated in and around known infected areas in 2004 according to Crossley, but beginning in 2005, statewide surveillance will resume.

“We don’t expect statewide surveillance to be on the scale of 2002, when we sampled over 40,000 deer in one year, but we do want to continue watching all areas of Wisconsin for any sign of the disease.

In addition to testing deer from the disease eradication zone (DEZ) and the herd reduction zone (HRZ) the department is testing hunter harvested wild deer in the vicinity of several deer farms where CWD-positive deer have been found.

New this year is the establishment of an eastern disease eradication zone (DEZ). The 321-square-mile eastern zone is located along the Wisconsin-Illinois border in southern Rock and Walworth counties. The existing western DEZ, located for the most part in Iowa and Dane counties has been expanded to 1,352-square miles. However, more than 80 percent of the positive deer are in a 126 square mile area bounded by Spring Green, Mazomanie, Black Earth, Mount Horeb, and Ridgeway. The eastern DEZ is formed around seven CWD-positive wild deer found in Rock County and two in Walworth County. Scientists believe this area is part of a separate core of infection centered in northern Illinois.

Maps of all CWD zones and CWD hunting regulations are available in the 2004 Wisconsin Deer Hunting Regulations pamphlet and on the DNR Web site.

Biologists have also learned that fawns have a low incidence of CWD – just 6 in 5,600 tested, and that disease prevalence increases with age and the rate of increase is faster in males than females. In the core area of the disease eradication zone, prevalence was similar in 2002 and 2003; approximately 5 percent of adult deer tested were positive. Within the center of the core area a few sections of land had prevalence of 8 to 12 percent.

“Analysis of the past two year’s surveillance results indicates that higher deer densities are associated with higher disease prevalence,” said Dr. Julie Langenberg, DNR wildlife veterinarian. “These results are similar to what researchers are finding in mule deer in Colorado. Taken together, this knowledge suggests that deer refuges in the disease eradication zone, places with high deer densities, could also be serving as disease refuges.”

Researchers at the University of Wisconsin – School of Veterinary Medicine have not been able to uncover any evidence of genetic resistance to CWD in white-tailed deer; virtually all deer in Wisconsin are considered vulnerable to the disease. This finding and monitoring of the disease here and in Colorado does not support the possibility that the disease will “burn itself out,” scientists say.

Again in 2004, the department will use sharpshooters to concentrate on areas of special interest for disease surveillance and herd reduction with the consent of landowners. Sharpshooters will also assist non-hunting landowners wishing to help in the population reduction effort.

One area where sharpshooters will deploy is in two experimental zones that scientists have dubbed “sparks” areas. The analogy comes from a wildfire where burning embers are thrown ahead of the fire line by wind, igniting new areas in advance of the main fire. In this case the sparks are CWD-positive deer found near Hollandale in Iowa County and in Orion Township in Richland County. Both these areas are quite a distance from the core area of western Dane and eastern Iowa counties. The object of the effort is to evaluate whether it is possible to put out a disease spark by reducing deer densities.

Rewards and free landowner permits

Last season, citizen comments led to creation of a cash reward system for harvesting deer and free landowner hunting permits in the disease eradication zone. This system will be in place again in 2004. A reward of $400 will be split evenly between a landowner and a hunter for any CWD positive deer shot anywhere in the state. All deer shot from the DEZ are eligible for a $20 payment in a lottery at the end of the hunting season.

Landowners in the Disease Eradication Zones and their guests will once again be able to hunt their property without purchasing a regular archery or gun deer-hunting license. What’s new in 2004 is that these permits can be purchased from any license vendor for a $2 processing fee. Gun hunting seasons are extended in both the HRZ (Nov. 20 – Jan. 3) and DEZ (Oct. 28 – Jan. 3). Landowners in the DEZ can continue to hunt until March 31 under the authority of their landowner permit. Unlimited Earn-a-Buck rules apply in both zones – hunters can shoot as many deer as they want as long as they shoot an antlerless deer first for every buck they shoot.

To help with the problem of excess venison that hunters can’t use there is a special venison donation program in place in the DEZ. Participating meat processors will store excess venison until CWD test results come back. Deer testing negative for CWD will be processed and donated to the food pantry program. This program addresses the concerns of hunters that deer they shoot in support of disease eradication not be wasted.

“CWD is going to be with us for some time,” says Crossley, “and it will affect management decisions and hunting regulations in infected areas for the foreseeable future. We will only be successful if we have support from landowners and hunters, not only in the disease eradication zones – but across the state.”

FOR MORE INFORMATION CONTACT: Al Crossley - (608) 275-3242