chronic wasting disease

States in the Midwest are continuing efforts to combat chronic wasting disease in deer populations. 

As of March 6, 2019, there were 270 counties in 24 states with reported CWD in free-ranging cervids. This map is based on the best-available information from multiple sources, including state wildlife agencies and the United States Geological Survey (USGS).

So far, chronic wasting disease is confined to deer in northern Illinois. But that could change in a hypothetical future.

The disease was first discovered in Illinois in 2002. It is believed to have spread from southern Wisconsin.

“The initial outbreak was near Roscoe, right on the Wisconsin line,” said Doug Dufford, a retired biologist with the Illinois Department of Natural Resources who may be the foremost expert on the prevalence of the disease in Illinois. “In 2002 we detected our first one in November. Wisconsin picked up their first one in January. We believe our outbreak was associated with the Wisconsin outbreak.”

Several hundred deer in Illinois have been infected, IDNR has reported. That translates to a 1% infection rate, which has stayed relatively level since the initial outbreak.

CWD is a neurological disease appearing in deer, elk, moose and other members of the cervid family. It is always fatal. The disease cannot be transmitted to other species, and there is no evidence of CWD being transmitted to humans.

The causative agent is an infectious protein called a prion.

“Non-cervid animals do not seem to be susceptible unless you use some radical methods, like injecting prions into the brain,” Dufford said. “That’s what we know now. But there is also a lot of evidence to suggest that these prions can mutate over time.

“A real concern is that these prions can build up in the soil and can be incorporated into the roots of plants, and into the vegetative material as well. They don’t decay very rapidly. They can remain for period of five years in the soil.”

In parts of Wisconsin, it’s infecting more than every other adult male in the deer population, Dufford said. The rate has been doubling every four to five years.

Wildlife biologists are concerned about the spread of the disease. A report published last year by IDNR determined that from 2002 to 2010, 80% of all CWD-positives identified in the state originated in either the counties of Boone or Winnebago. But in 2018, only 14% came from those counties.

“This shift in CWD distribution has posed significant challenges for management, because management must now be directed over a far larger area, spreading resources very thin,” the report said.

“Disease management strategies in Illinois have been successful in controlling CWD prevalence rates at low levels, but in many management units the number of deer removed by sharpshooters is currently insufficient, whether because of limited access to property or because of our limited resources.”

Nat Williams is Southern Illinois field editor, writing for Illinois Farmer Today, Iowa Farmer Today and Missouri Farmer Today.