While Chronic Wasting Disease (CWD) hasn’t been found in the Northern Wilds, the always fatal deer disease remains on the march in Minnesota. Now endemic in wild deer in southeastern Minnesota, the disease has been found at deer farms elsewhere in the state, most recently at a facility in Beltrami County. This new discovery is the northernmost location where CWD has been found in Minnesota.
Since the incidence of CWD in wild deer is often closely associated with nearby infected deer farms, the Beltrami case is alarming for the wildlife managers tasked with stopping the spread of the disease. When CWD is detected in a farmed deer, all of the cervids at the facility are killed and usually incinerated. The farmer is compensated by the USDA for the lost livestock.
CWD infects not only deer, but also other Minnesota cervids such as moose and elk. The disease is difficult to detect until its final stages, which may be two years or more from the initial infection. There is no cure. Current testing requires brain or lymph node tissue from a dead animal.
CWD is what is known as a protein misfolding disease. Proteins are nonliving components of the body and thus don’t respond to treatments such as vaccines or antibiotics. Prions, as the misfolded proteins are called, can persist in the environment for more than a decade. In hooved animals, other protein misfolding diseases include scrapie in sheep and bovine spongiform encephalopathy (Mad Cow Disease) in cattle. Related human ailments include Creutzfeldt-Jacobs Disease, Alzheimer’s Disease and Parkinson’s Disease.
Research into related diseases is informing efforts to stop the spread of CWD on the landscape. Recently, researchers at the University of Minnesota’s Center for Prion Research and Outreach (MNPRO) developed a field test for CWD detection that provides results within 24 hours. For hunter harvested deer, CWD detection required sending tissue samples to a distant lab and then waiting, sometimes weeks, for results. This is difficult for hunters, who are advised by the Centers for Disease Control not to eat venison that tests positive for CWD. With the rapid turnaround of the new test, if it becomes broadly available, they will know if they can safely process and eat their venison.
The new test relies on nanotechnology, which is commonly used to detect other diseases.
“We identified a nanoparticle that changes color when it interacts with the misfolded protein that causes CWD,” said Dr. Peter Larsen, co-director of MNPRO.
The new test uses relatively inexpensive equipment (less that $10,000) that can be set up at a DNR field station and complete the test on site. The test is called MN-QuIC, which is easier to say that Quaking Induced Conversion, which is the testing method. Larsen explained there is a whole family of tests for other diseases that use this method.
The new test is a positive development in the fight against CWD and it is important that hunters continue hunting, rather than giving up in frustration or due to fear of not knowing whether the deer they’ve killed has CWD. Larsen emphasized that hunting and predation on deer by wolves or other large predators are two tools wildlife managers can use to limit the spread of CWD on the landscape. In the absence hunting and predation, deer numbers quickly multiply, greatly increasing the possibility of CWD transmission from close contact among the animals.
The next level of testing is finding ways to detect CWD in living animals and the environment. Researchers have detected CWD prions in water. There is also some evidence that the prions can be taken up by plants, possibly creating another vector for infection when deer feed on them. New breakthroughs to achieve this level of testing are occurring in the MNPRO molecular lab. This will allow wildlife managers and deer farmers to address CWD in real time with sophisticated surveillance of deer farms and animals that are moved from one facility to another.
“Traditional CWD testing methods are limited for detecting early-stage infections and thus it seems we are always one to two years behind, because that how long it takes for prions to accumulate in an infected deer and to show symptoms,” Larsen said. “We need faster and more sensitive tests that provide an accurate, real time view of CWD on the landscape.”
Is reigning in the spread of CWD really that important? Larsen’s answer is an emphatic “yes.” As with other diseases, CWD has variants. It is possible a variant could be transmissible to other domestic livestock or humans. In southeastern Minnesota, where CWD is endemic, testing has found CWD in one or two percent of wild deer. In contrast, some counties in Wisconsin have found CWD in 50 percent of the bucks harvested by hunters. Since the fawns of infected does can be born with CWD, it is possible high rates of infection could result in deer herds predominately comprised of young deer. A fawn born with CWD may survive about two years—long enough to produce infected offspring.
The economic importance of deer must be considered, too. Over a half million Minnesotans participate in deer hunting. They purchase hunting licenses that fund state wildlife management, as well as gear and supplies. They also buy land for places to hunt. In many rural locations, the loss of deer hunting would result in lower land values. There are social aspects, too. Many folks enjoy seeing deer and having them around their homes. This is unlikely to be the case if a high number of animals are infected with CWD.
Larsen believes we are on the cusp of having the detection tools we need to become proactive in CWD management. While we have no control of the management strategies of other states, such as Wisconsin, we may be able to prevent the rise of CWD within Minnesota. Also, what researchers learn by addressing the challenges presented by CWD may be applied to other prion diseases, including ones affecting humans.
“At MNPRO, our position is that we need to think outside the box and embrace new technologies so we can throw everything we have at CWD to stop the spread,” Larsen said. “Now that we’re having success, we need to build on it. Anything is better than the status quo.”