Wisconsin mobilizes to battle chronic wasting disease

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Wisconsin mobilizes to battle
  chronic wasting disease

Wisconsin's Department of Natural Resources wants hunters to depopulate an estimated 15,000 white-tailed deer in a 287-square-mile zone to halt the spread of chronic wasting disease, a transmissible spongiform encephalopathy of North American deer and elk. Department officials are also proposing reductions of up to half the deer populations in 14 counties.

Chronic wasting disease was found for the first time in Wisconsin this February in three randomly sampled bucks. Subsequent testing of 516 deer revealed 11 more infections. Now, the state's deer and elk populations, along with its $1 billion hunting industry, are threatened by a disease researchers are just beginning to understand.

"I cannot emphasize enough that hunters and landowners hold the keys to dealing with chronic wasting sickness," said Darrell Bazzell, secretary of the state Department of Natural Resources, in a statement. "If we want to have healthy deer and deer hunting in the future, we're going to have to do some hard things now—open our lands and start the very sad task of drastically reducing deer numbers in the CWD zone."

Tissue Samples

Sport hunting is a key part of Wisconsin's economy and culture. After the spring fawning season, the free ranging white-tailed deer population is expected to peak this fall at around 1.5 million, making Wisconsin fertile ground for hunting enthusiasts. Moreover, the state economy relies on revenue generated during deer season, which traditionally runs from September through January. Interstate commerce of farmed elk and deer contributes to the economy as well.

But CWD could change all that. Texas announced this March that it was closing its borders to Wisconsin deer and elk imports. "We're very concerned," said Bob Manwell of the Wisconsin Department of Natural Resources. "We're treating it as a very serious threat to the health of our herd here, which is why we've moved so quickly, trying to depopulate that area."

Governor Scott McCallum has asked the federal government for $18.5 million and has directed an additional $4 million in state funds to fight what his administration is calling the most serious animal health crisis in Wisconsin's history.

Chronic wasting disease is a degenerative brain disease in cervids characterized by weight loss leading to death. It was first recognized in 1967 in mule deer at a wildlife research facility in northern Colorado. The disease was found in free-ranging deer and elk in Colorado, Wyoming, and Nebraska in the mid-1980s, and later in farmed herds in South Dakota, Nebraska, Oklahoma, Montana, and Colorado.

The U.S. Department of Agriculture issued an interim rule in February regarding a nationwide CWD surveillance and indemnity program for farmed elk herds. In April the USDA agreed to purchase around a thousand farmed elk in a part of Colorado where the disease is endemic in free-ranging animals. At this time, there is no live animal test or vaccine for CWD.

The cause and transmission of CWD are not known. Theories about the cause range from an abnormal prion to an unconventional virus. There is no evidence that other ruminant species are infected through contact with CWD-infected deer or elk. Nor are there any known health risks to humans eating meat from infected animals, although handling, processing, and consumption precautions are recommended.

Wisconsin has been monitoring its white-tailed deer for disease since the 1990s, starting with bovine tuberculosis. The surveillance program was expanded in 1999 to include CWD. Hunters voluntarily submit samples from culled deer, which are tested at the National Veterinary Services Laboratories in Ames, Iowa. More than a thousand deer were tested in that time, all with negative results.

But on Feb. 28, Wisconsin officials were notified that three submissions from the 2001 hunting season had tested positive for CWD. The infected deer had been killed in western Dane and eastern Iowa counties, and 11 additional infections were later discovered that area. How CWD was introduced in Wisconsin and the number of infected cervids are not known, however.

Based on a sampling analysis, the state Department of Natural Resources established a 287-square-mile eradication zone around the infection sites. Special hunting permits are being issued to landowners in the eradication zone, home to an estimated 15,000 deer, to start culling as many of the animals as possible. Owners can do the hunting themselves, or allow others to depopulate deer on their property.

"Our goal there is to eliminate the disease by bringing the white-tailed population just as low as we possibly can, as close to zero as we can get it," Manwell said. "If [CWD] is contained in as small an area as we think it is right now, based on what we know, we might stand a chance of eradicating it."

Original Deer

On another front, efforts are under way to reduce deer populations between 25 percent and 50 percent in 14 Wisconsin counties. The department has asked the state Natural Resources Board for emergency rules to amend deer-hunting protocol to facilitate this plan. The rules, which address a variety of issues ranging from the types of hunting weapons that can be used to the number of deer that a single hunter can kill, are expected to be implemented in June.

Landowners and hunters have been asked to observe a voluntary ban on feeding deer in the eradication zone and adjacent areas, as the practice is thought to facilitate the spread of CWD. A series of public meetings were held across the state to educate the residents and to also gather their comments as part of the rule-making process.

The state is exploring the possibility of developing its own internal CWD testing capabilities. One option, Manwell explained, is expanding the state veterinary diagnostic laboratory at the University of Wisconsin in Madison, with the aim of testing up to 15,000 samples by fall. But for this to happen, he said, funding and facility issues must first be addressed.