New Research Zeros in on How CWD is Spreading

Before there was a clear understanding of how CWD prions could and could not be transmitted by the environment, there was always the question of when an infected area was free of the disease.

New Research Zeros in on How CWD is Spreading

Featured photo:  Kansas Department of Wildlife, Parks and Tourism

Salt licks and areas where deer and other wildlife congregate have been thought to aid in the spread of chronic wasting disease (CWD), and now that suspicion is confirmed, thanks to new research by the University of Wisconsin (UW).

According to the Milwaukee Journal Sentinel (MJS), “Scientists detected the prion that causes chronic wasting disease in soil and water at mineral lick sites in south-central Wisconsin.” This research was made available in a research publication released May 2.

“Detection of prions in environmental reservoirs represents an important first step in understanding environmental transmission of CWD as well as the potential for cross-species transmission," Joel Pedersen said to MJS. Pedersen, the lead author of the study, is a professor of Soil Science, Chemistry and Civil and Environmental Engineering at UW.

Why Is This Research Critical to Sustaining Deer Hunting in the U.S.?

Without an aggressive campaign to slow the spread of CWD, Mike Samuel, an emeritus professor of wildlife ecology at UW, believes as many as 50 percent of Wisconsin’s adult male deer population and 25 to 30 percent of the female population will be killed by the disease before it finally slows down on its own, according to

If you’re not a resident of Wisconsin, don’t turn away just yet. Animals infected with CWD have been identified in 24 U.S. states and three Canadian provinces.

Related: The New York Times Drops Report on How CWD Is Threatening Deer

Before these recent findings, there was no clear understanding of how CWD prions could and could not be transmitted by the environment. There was always the question of when an infected area was free of the disease. For instance, an area may harbor deer infected by CWD, yet the area would remain infected for years after the infected animals were removed.

Now, with the detection of prions in soil and water, it’s much clearer when a contaminated area is considered cleaned up.

“Having an analytical technique to detect the presence of CWD prions is valuable to establish an environmental vector as well as support steps (wildlife) agencies should be taking to address the disease,” said Tom Hauge to MJS. Hauge is a retired director of wildlife management for the Wisconsin Department of Natural Resources.

The study sampled 11 lick sites from 2012 through 2015. Subsequent testing found the CWD prion at nine of 11 sites. To identify prions in soil and water samples, scientists used a technique known as protein misfolding cyclic amplification (PMCA).

The licks, typically used by hunters and farmers to draw animals to a site and add minerals to the animals’ diets, are used by free-ranging deer, livestock and non-cervid wildlife species.

Levels of prions detected at these sites were considered low, which may be due to the difficulty of separating prions from the soil. Regardless, researchers haven’t determined how many prions are needed before a deer begins to show symptoms of CWD.

"Longer term, we also hope to better understand how direct and indirect sources of transmission play into CWD outbreaks," Pedersen told MJS. "We're hopeful our recently published work will help advance work in this area."

Hunters and CWD: A Long Way From Critical Mass

Before the 2000s, CWD was considered a “Western” disease because it appeared to be confined to the Wyoming and Colorado region. By 2005, the disease had jumped the Mississippi River and was headed east. New York and West Virginia found their first cases of CWD in 2005.

Within the hunting and wildlife communities, there have been concerns that hunters are in denial. Back in 2015, Don Bates, former supervisor of chronic wasting disease operations for the Wisconsin Department of Natural Resources said in an interview with Wisconsin outdoor writer and Whitetail Journal contributor Patrick Durkin that people tend to ignore CWD.

Bates, now retired, said most deer stricken with CWD die unseen and undocumented in thickets, wetlands or river bottoms.

“If CWD wasn’t such an insidious unseen killer — if it had teeth, claws and hair — the hunting public would be outraged by it,” Bates said. “They want the problem to go away. They’re not talking about it. They’re in denial, but it’s not going away. It’s getting worse at faster and higher rates than ever.”

Maybe that silence is changing. There are signs hunters are beginning to talk about the problem. It stands to reason hunters are nearing a tipping point where the spread of the disease is so great it can no longer be ignored.


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