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CWD prevalence grows exponentially in local area
CWD Prevalence Growth

DRIFTLESS - Experts who monitor the spread of Chronic Wasting Disease (CWD) in the Southern Farmland District in Wisconsin are sounding the alarm bells. The increase between 2002 and 2018, as the fatal disease affecting whitetail deer spread northwest from western Dane and Iowa counties, through Richland County, and now up into Vernon County, has epidemiologists worried about the future of the deer population in our area.

At a CWD Summit, held at the Kickapoo Valley Reserve on Thursday, May 9, nearly 100 citizens showed up to hear Doug Duren, a Richland County landowner/hunter who is dealing with CWD positive deer on his property. Bryan Richards, Emerging Disease Coordinator with the United States Geological Survey (USGS) National Wildlife Health Center, the country’s leading expert on Chronic Wasting Disease and a native of Monroe County, discussed the current state of CWD in Wisconsin and what are the implications to the Wisconsin deer herd.

Doug Duren, a landowner from Richland County, is the fifth generation of his family to have hunted their 400-acre property in Cazenovia. His family has been on the front lines of the spread of CWD into Richland County.

“Sixty years ago, when my family would hunt our land, we didn’t see very many deer,” Duren said. “Now, it’s completely different, and there are deer everywhere.”

Duren explained that 85 percent of Richland County is covered in deer habitat. Of that percentage, he pointed out, 95 percent of it is privately owned land. When CWD was first discovered in 2002, the prevalence of it in the deer herd was less than one-tenth of one percent.

“It used to be just the older males that were testing positive, but last hunting season, of the 50 deer killed on our farm, three of them tested positive,” Duren explained. “Those deer were a one-and-one-half-year-old male, and two, two-and-one-half-year-old males.”
“It used to be just the older males that were testing positive, but last hunting season, of the 50 deer killed on our farm, three of them tested positive,” Duren explained. “Those deer were a one-and-one-half-year-old male, and two, two-and-one-half-year-old males.”
Doug Duren, Richland County landowner/hunter

Duren explained that due to lack of other management options available at the state level, the best tool that citizens have to try to control its spread is their firearm. For that reason, given the alarming growth in prevalence of the disease in the Richland County deer herd, Duren and his family try to invite lots of people to hunt on their land. And they insist that every deer taken on their land be tested for CWD. The family sponsored a CWD testing station and dumpster for disposing of carcasses in the 2018 deer hunting season.

At the crisis point

Bryan Richards with USGS has been researching CWD for years. He was quick to explain to meeting participants that the spread of the disease, from an epidemiological standpoint, is on the point of an exponential leap in this area.

“I grew up on a 600-acre farm near Cataract in Monroe County,” Richards explained. “When I was young, you hardly saw any deer, and at the same deer stand in 1985, I saw 160 deer.”

Richards pointed out that the growth in the deer herd is beginning to have an impact on farming operations. He emphasized that managing for recreation and managing to control disease are very different management strategies. He also pointed out, though, that even though one of the best management strategies for controlling the spread of disease is to shoot antlerless deer, Wisconsin as a dairy state has a legacy of discomfort with shooting female animals.

“Dairy farmers derive their livelihoods from the females in the herd,” Richards said. “This is one of the reasons there has always been opposition in the state to shooting the does.”

Richards told participants that between 2001 and 2018, there were 228,000 deer sampled for CWD in Wisconsin. After the legislature eliminated deer registration stations, the sampling was purely voluntary. By the end of 2018, over 5,200 CWD-positive deer had been detected in 26 Wisconsin counties.

“One third of adult male deer shot and sampled in 2018 tested positive for CWD,” Richards said. “The disease has overtaken Richland County, is beginning to spread north and west into Vernon County and also up the Wisconsin River into Adams and Portage counties.”
“One third of adult male deer shot and sampled in 2018 tested positive for CWD,” Richards said. “The disease has overtaken Richland County, is beginning to spread north and west into Vernon County and also up the Wisconsin River into Adams and Portage counties.”
Bryan Richards, Emerging Disease Coordinator with the USGS National Wildlife Health Center

Richards told a story about Buffalo County, which is considered to the number one deer hunting county in the nation.

“Buffalo County’s Citizen Deer Advisory Council (CDAC) met and were so alarmed about the possibility of CWD infecting the county’s deer herd, they proposed an “antlerless only” deer season for 2019,” Richards said. “The DNR denied their recommendation, the only time they have ever gone against a CDAC recommendation.”

What is CWD?

CWD is one of a class of diseases known as ‘Transmissible Spongiform Encephalopathy’ (TSE). ‘Transmissible’ means it can be spread between animals. ‘Spongiform’ means that it resembles a sponge. ‘Encephalopathy’ means that it is a disease of the brain.

Other TSE-type diseases are Scrapie, which affects sheep; Bovine Spongiform Encephalopathy (BSE) or ‘Mad Cow Disease,’; and the spongiform encephalopathies that affect mink and felines. TSE characteristics include a long incubation time, progressive neurological deterioration, uniform fatality, transmissibility through food, blood, body fluids, etc., confirmation is post mortem, there is no known vaccine or treatment, it crosses the species barrier, and is caused by prions.

“Basically a prion is a protein, a chain of amino acids that is folded in a certain way,” Richards explained. “What happens with CWD is that the disease causes the proteins to unfold themselves, and then refold in a different way.”

Richards explained how his team had tried various extreme methods in the laboratory to destroy the CWD prions, such as incineration, high pressure, etc., and none of the methods had worked.

“You can’t cook the prion out of the meat,” Richards said. “The prion will also not cause your body’s immune system to try to defend itself, so there will not be observable signs of infection.”

Richards was quick to say that scientists have not documented a case where CWD has jumped from deer to humans, but he says that other TSEs like Mad Cow Disease had made the jump. He said that canines, like dogs, coyotes and wolves, seem to have immunity from it even if they are eating the flesh of infected deer. 

The disease is spread by feces, saliva, urine, coughing and sneezing. The prions remain active in the environment a very long time, and can be spread from area to area by infected soil on tires. It also can be taken up from the soil into plants, and be spread by healthy animals consuming infected plants or by transporting infected hay into other areas than where it is grown. Any place where deer gather in numbers can be a transfer point for the disease, such as deer farms, deer baits, and even deer plots.

“Basically, at this point, 20 percent of 18-month-old deer have CWD,” Richards said. “Even though a case where the disease has jumped from deer to humans has not been documented, the World Health Organization advises against eating meat from animals that test positive.”

Management

Richards said the keys to managing the spread of the infection are prevention, monitor new outbreaks, support ongoing research, and provide timely and accurate information to stakeholders.

To prevent the further spread, he says hunters should

• stop moving deer

• dispose of carcasses appropriately and don’t allow discarded parts to end up on the landscape

• stop artificial congregation of deer

• address other potentially infectious agents

• test your deer for CWD to help create a better data set for researchers and to ensure that your family is not consuming meat from an infected deer

The number one priority is to manage the disease where it exists. He pointed to the ‘Earn a Buck’ program that existed from 2002-2008 as the best management tool the state had ever had to fight the spread of the disease. Beyond measures like that, or some sort of targeted, wholesale slaughter of the herd in an infection hotspot area, the other tools are to increase the harvest of bucks, particularly older bucks, and consider allowing hunting of bucks while they are in rut.

 “Given the tools available to us right now, your gun is the best management tool we have available,” Richards said. “We need more hunters in the field shooting more deer.”