student fitting a captured white tail deer with a GPS collar

Michael Egan, a doctoral student at Southern Illinois University Carbondale, prepares to fit a captured white tailed deer with a GPS collar. Egan is collaborating with the Illinois Department of Natural Resources to better understand where deer are likely to come into contact and spread chronic wasting disease, an affliction of deer, elk, reindeer, moose and other species in North America and beyond. (Photo provided)

June 15, 2022

SIU doctoral student researches how a devastating disease spreads among deer

by Tim Crosby

CARBONDALE, Ill. – White-tailed deer are so plentiful in Southern Illinois that seeing a group of them sauntering through a neighborhood at dusk or dawn is almost as common as seeing a squirrel. The animal is also a mainstay on the campus of Southern Illinois University Carbondale, where woods and waterways meander among the academic buildings and residence halls, inviting wildlife of all kinds.

The university’s bucolic setting is one reason zoologists at SIU have a long-standing partnership with state biologists, studying many aspects of the deer’s life, from its interactions with other species to its interface with humans. One of the latest such efforts has a doctoral student investigating how deer come into contact with one another, with an eye toward better understanding how a devastating disease spreads.

Michael Egan, a doctoral student in zoology, is collaborating with the Illinois Department of Natural Resources (IDNR) to better understand where deer are likely to come into contact and spread chronic wasting disease, an affliction of deer, elk, moose and other species in North America and beyond. Working with Guillaume Bastille-Rousseau, assistant professor at SIU’s Cooperative Wildlife Research Laboratory, Egan is trying to understanding where and how CWD may spread, which is important for managing the disease.

The work also has taken on a more recent twist, with the researchers investigating whether deer can act as “reservoirs” for SARS-CoV-2 in Southern Illinois, the virus that causes COVID-19, between the typically more infectious winter seasons.

Expanding knowledge

CWD is spread by prions, a misfolded protein that can be transferred through direct interaction or indirectly when one deer sheds prions through feces, urine, blood or saliva and another deer comes into contact with them. Once a deer is infected, it may take more than a year to develop symptoms, which include drastic weight loss, stumbling, listlessness and other neurologic indicators.

Consistently fatal, CWD can affect animals of all ages, and some infected animals may die without ever developing the disease. The disease is in the state, but not currently in Southern Illinois; however, it is important to study deer behavior in environments without CWD infections, Egan said.

“Our goal is to use GPS collars to track the movements of white-tailed deer to determine their habitat associations and where deer come in contact with each other,” he said. “We also want to study patterns in deer contact, like how often deer make contact with members of the same sex relative to the opposite sex, and the rate of contact within versus between social groups.”

A constant threat

To date, wildlife officials have confirmed cases of CWD in 17 Illinois counties: Winnebago, Boone, McHenry, DeKalb, Ogle, LaSalle, Stephenson, Jo Daviess, Kane, Grundy, Kendall, Du Page, Lake, Will, Livingston, Kankakee and Carroll. Deer throughout the state hold great ecological, recreational and economic value.

Scientists also worry about CWD’s potential ability to “jump” to other species, including humans. Another prion protein-related disease, so-called mad cow disease, did make that transition, with lethal results of variant Creutzfeldt-Jakob disease. So far, however, evidence indicate humans have a strong biological barrier against CWD.

Sampling the population

To find out more, researchers must get up close and personal with an animal known for its swift, elusive nature. Egan’s project is capturing deer mainly in two locations: SIU’s Touch of Nature Environmental Center, south of Carbondale, and near Lake Shelbyville in Central Illinois on land owned by the Army Corp of Engineers.

To capture the animals, Egan primarily uses “clover traps,” which are basically baited net enclosures with a trap door. Once a deer enters and the door closes behind it, the net collapses and safely secures the deer until researchers can administer tranquilizers.

After the drugs take effect, Egan fits the deer with a GPS collar, takes measurements and collects samples such as blood.

The researchers also use drop nets above baited areas to capture several deer at the same time. Finally, they sometimes use dart guns to administer a tranquilizer from a distance to specific types of deer – adult bucks, for instance – that they may need to compare behavior between the sexes.

“GPS collars record the position of deer every few minutes and allow us to determine where and how deer move,” Egan said. “Once data is collected, we use statistical models to evaluate the behavior of the deer. Mainly we look at where the deer are and what the habitat at those locations is typically like; however, we also do things like determine when deer are most active and when they come in close proximity to other deer to determine when they may be coming in contact with each other.”

How it works

Egan is particularly interested in whether contacts among deer occur in areas deer rarely visit, rather than their normal locations. For example, a human may spend most of their time at home, but come into contact with other people most often at the gym or a bar.

“So deer may also spend most of their time in one habitat, but come in contact with other deer in totally different habitats,” Egan said. “So far, we are finding that deer may be most likely to come in contact with each other in areas they don’t usually select for most strongly.”

Although SIU has worked for years with IDNR, Egan began his project just over two years ago. The study is central to his doctoral efforts, and the work will likely continue after he graduates in a few years.

Deer and COVID-19

Researchers in other areas previously discovered that some deer were carrying the SARS-CoV-2 virus, suggesting it may pass between humans and that species. Such a dynamic could mean that deer act as a reservoir for the virus during the less infectious seasons before spreading back into the human population.

To find out more, Bastille-Rousseau’s began taking blood samples in 2022 specifically to test for the virus.

“If deer can act as a reservoir for the virus, it’s important to understand where deer populations are infected with SARS-CoV-2 and how it spreads in the population,” Egan said. “It’s especially important to identify areas with the greatest risk of transmission between deer and humans.”

The researchers take blood from as many captured deer as possible, process the sample at SIU and then send it to a U.S. Department of Agriculture laboratory for testing.