New U of M resources provide cutting-edge information on chronic wasting disease.
Deer hunting draws thousands into the fields and woods each fall, particularly in Minnesota. In addition to being a family tradition for many, conservationists and scientists rely on deer hunters to cull herds to sustainably manage the wildlife population.
In recent years, however, hunters have been cautioned to be on the lookout for deer who look skinny or behave oddly, and to report those sightings to authorities. That’s because in the late 1960s, a new disease entered the equation—chronic wasting disease or CWD—that affects deer and their relatives.
CWD, first detected in a captive deer population in Colorado and now found in at least 26 states and internationally, is a rare, progressive neurodegenerative disorder that is fatal to deer and other cervids, including moose, elk, and reindeer. It belongs to a family of diseases called TSEs (transmissible spongiform encephalopathies), also known as prion diseases. There is no vaccine or treatment for the condition.
According to the Centers for Disease Control and Prevention (CDC), although the overall occurrence of CWD in free-ranging deer and elk remains relatively low, in certain areas the infection rate of herds can be as high as 1 in 10, or even higher in particularly hard-hit areas. In Minnesota, the disease has been detected to date in several counties: Crow Wing, Fillmore, Houston, Olmsted, and Winona. CWD has also been found in Canada, South Korea, Finland, Norway, and Sweden; cases have spiked in the past five years.
The CDC also says that CWD may have an incubation period of more than a year before deer or other affected animals show signs of infection.
While to date no reported cases of CWD infection have ever been found in people, concerns remain about the unknown properties of prion diseases, including CWD.
To sort through this confusion, the University of Minnesota’s Center for Infectious Disease Research and Policy (CIDRAP) has designed an online resource center to help public health officials, wildlife managers, scientists, and public policymakers better understand the disease.
The new online Resource Center—found at cidrap.umn.edu/cwd—is part of CIDRAP’s Chronic Wasting Disease Response, Research, and Policy Program, a national initiative created to combat CWD and to respond to any potential for additional animal-to-animal or animal-to-human transmission of the disease.
The decision to launch the center was a natural for CIDRAP, according to its director Michael Osterholm, a U of M Regents Professor and the McKnight Presidential Endowed Chair in Public Health. In the 1980s, Osterholm was part of a group of researchers who worked to determine if there was a risk of transmitting CWD from animals to humans. At the time, the consensus of experts was an emphatic no. Today, Osterholm and other infectious disease experts are concerned that those earlier predictions may have been too optimistic. “One of the challenges is you can’t assume that the absence of cases today means absence of clinical cases tomorrow,” he explains.
Case in point: Osterholm says that the incubation period in humans, should they ever contract CWD, could be between 10 and 40 years. But the bigger concern has to do with the fact that CWD prions—proteins that can trigger normal proteins in the brain to fold abnormally—have mutated over time.
“If Stephen King were to write a novel based on an infectious agent, he would write it about prions,” says Osterholm, noting that the proteins are heat-resistant to almost 1,500 degrees Fahrenheit and immune to most chemical degradations. “Once they contaminate the environment, they can reside in the soil and eventually get picked up in plant material.”
Although research continues, scientists currently think CWD spreads by contact with contaminated body fluids or tissue, or through exposure to CWD in the environment. And even in the absence of potential animal-tohuman CWD transmission, other scenarios involving CWD include more aggressive animal-to-animal transmission, which could be disastrous for North America’s moose and caribou populations.
Preventing such catastrophic outcomes is the goal of the new center, which includes up-to-date news about CWD, maps that track the disease, and legislative initiatives that have been introduced to address CWD. There’s also a FAQ on what hunters and others can do to reduce their exposure to CWD. (Health experts advise people not to eat animals that show any signs of infection—although the symptom-free incubation period for CWD remains a concern.)
In addition to the new resource center, this past June the U of M’s College of Veterinary Medicine and a multidisciplinary team it assembled received more than $1.8 million from the Minnesota Environmental Trust Fund and an additional $200,000 from the Rapid Agricultural Response Fund to find a better way to reliably test for CWD. The goal of the group is to develop a quick way for hunters to have deer carcasses tested after harvest to ensure no CWD is present.