AgBioResearch

More than 600,000 Michiganders take to the woods in pursuit of white-tailed deer each year. For many, the hunt represents more than a chance to secure fresh food. In many instances, the opening day of deer hunting season is treated like a holiday.

An activity rife with nostalgia in the Great Lakes State, deer hunting is often a multigenerational pastime where stories of chasing trophy bucks are ingrained in community folklore. But this heritage and its future are threatened by a fast-spreading, highly contagious condition called chronic wasting disease (CWD).

Caused by an abnormal form of cellular protein called a prion, CWD affects deer, elk and moose. It is among a class of conditions known as transmittable spongiform encephalopathies, meaning that it’s an infectious and degenerative neurological disorder. One of the most well-known examples of this type of disorder is mad cow disease.

Animals with CWD may have no discernible symptoms for years. However, in advanced stages they may show odd behavior, emaciation, listlessness and loss of bodily functions. All CWD cases eventually result in death.

Identifying CWD in a live animal can be tricky. The only way to ensure an accurate diagnosis is a postmortem examination to check for prions in the brain, lymph node or tonsil tissue.

Colorado was the first state in the U.S. to detect CWD – in a captive facility in 1967. States in the western part of the nation have been battling the disease in free-ranging deer since the early 1980s. Now in 25 states, CWD was first discovered in free-range deer in Michigan in 2015.

Studies have not shown CWD to be transferable from deer to humans, but research is ongoing. Mad cow disease, which shares many characteristics with CWD, has caused more than 200 individuals to develop a human form of the disorder called Creutzfeldt-Jakob disease.

A research team at Michigan State University (MSU) led by William Porter, holder of the Boone and Crockett Chair of Wildlife Conservation, is studying CWD in hopes of curbing its spread. Porter first encountered the disease in 2005 while working as a professor at the State University of New York College of Environmental Science and Forestry.

“Once established, chronic wasting disease is extremely difficult to eliminate from a landscape,” Porter said. “Prions can persist in the environment for a long time, and there’s no established method to get rid of them.”

Porter and his colleagues used a modeling technique that integrated information on deer movement and interactions, followed by a thorough culling strategy, to help prevent CWD from gaining a foothold in New York. By 2010, five years after, no new cases had been found.

“We were seeing positive results in New York in large part because we were addressing CWD early,” Porter said. “In Michigan, we need to find solutions before the problem becomes widespread.”

Sonja Christensen, a research associate at MSU, leads several efforts in fighting deer diseases on behalf of Porter’s laboratory.

“Deer hunting is a big part of the culture in Michigan, of course,” Christensen said. “But there’s a conservation aspect to deer hunting that’s critical for many species. More than 50% of funding for all wildlife conservation in Michigan is generated through sales of deer hunting licenses.”

Christensen said a significant reduction in hunter participation due to concern over CWD management or a notable deer population decline could be disastrous. She added that Wisconsin has already experienced a decline in hunters because of conflicting opinions on management between hunters and agencies.

In partnership with the Michigan Department of Natural Resources, MSU researchers are confronting CWD from a multitude of angles.

MSU doctoral student Jonathan Cook is using modeling that combines risk factors in natural deer behavior and interactions with humans to learn more about where and why CWD is spreading.

“We’re trying to position management agencies to take proactive measures rather than learning about large clusters of CWD and then reacting,” Cook said. “Using our innovative models, we’re starting to put numbers on things that have been historically difficult to quantify, such as live animal movement or carcass movement from one place to another.”

To track movement patterns, deer are being captured and fitted with GPS collars, work led by doctoral student Jonathan Trudeau. Deer movement is a primary catalyst for disease distribution, and researchers hope that this exercise will yield much-needed information.

In cooperation with management agencies, MSU scientists are also exploring cost-effective approaches for lessening risk factors. In September, MSU hosted a meeting of 46 representatives from universities and management agencies in the inaugural meeting of the CWD Research Consortium. The group is collaborating on CWD research across multiple disciplines and thematic areas.

“We’re fortunate to have a talented team of scientists at MSU who bring a range of expertise on wildlife ecology and quantitative research methods,” Christensen said. “It’s going to be crucial to work with as many partners as possible moving forward.”