Chronic Wasting Disease (CWD)

By Misi Stine, Environmental Educator and member of the MN Herpetological Society

White Tailed Deer

Lwolfartist, CC BY 2.0, via Wikimedia Commons

There has been a lot in the news about Chronic Wasting Disease (CWD) in recent months, so it seems timely to write an article on the topic and discuss its impacts on wildlife.  CWD is part of a group of neurological diseases called spongiform encephalopathies (TSE’s) which are believed to cause abnormal proteins to form called prions. Proteins become abnormal and contagious when the protein material folds incorrectly.

Elk. Photo by David J. Stang, CC BY-SA 4.0, via Wikimedia Commons

 Other diseases in this group are scrapie, found in domestic sheep and goats for over 200 years, and bovine spongiform encephalopathy or “mad cow disease” found in cattle and Classic & Variant Creutzfeldt-Jakob Disease. The Classic form occurs in one out of a million humans worldwide. The Variant form has been found with large-scale outbreaks of mad cow disease in Europe.

CWD is found in the cervid family which includes deer, moose, caribou, elk and reindeer.  The disease was first identified in captive mule deer in the late 1960’s in Colorado. Today, it is found in 30 states, parts of Canada, South Korea and Scandinavia.  

When an animal is infected with CWD it causes spongy degeneration of the brain.  The disease is transmitted through direct contact between animals where an infected animal sheds the prion through bodily fluids (blood, saliva, feces, urine), antler velvet and the carcasses of dead infected animals. In addition, it can be spread through the environment.   Deer may not show symptoms for one to three years after exposure. Symptoms include weight loss, loss of fear of humans, drooping head or ears, confusion, excessive drooling or salivation and loss of control of their body. Once contracted, the disease is always fatal.

Hunter

FieldsportsChannel.tv, CC BY 2.0, via Wikimedia Commons

CWD was found in Minnesota in 2002 at an elk farm in Aitkin County. Since that time the Minnesota DNR has taken steps to curb the spread of the disease through surveillance of the wild deer population, and testing so it can be detected early. When these tests are positive the DNR can take action to try to keep it from spreading.  The first wild deer in Minnesota to test positive was in 2010.   As of 2020, there were 16 counties reporting positive cases of CWD. The DNR works in conjunction with Minnesota Board of Animal Health because deer and elk farms are classified as livestock operations and under their management.  The DNR has an extensive CWD response plan. Use the link to the left if you want to learn more about their efforts.

In May of 2023, the Minnesota Legislators agreed to add a mortarium on new white tailed deer farms as part of negotiations between the House and Senate on pending environmental legislation.  This change will likely bring the potential for a total ban on deer farms in the future. In addition to other regulations on existing deer farms, transferring regulatory oversight to the DNR from the Minnesota Board of Animal Health was included.  This is a strategy that they hope will slow the spread of CWD in wild deer protecting, cervid, and deer hunting which brings in an estimated $500 million dollars in revenue annually.

At this time, there is no effective way to treat CWD. Since a prion is an abnormal protein, scientist have not found a way to neutralize or  kill it. It does not respond to antibiotics, antifungals, antivirals, heat, or cold.  As a result, it can persist in the environment for long periods of time.  However, the Minnesota Center of Prion Research and Outreach at the University of Minnesota has found that the prions can be removed from stainless steel surfaces using a 1:1 solution of household bleach that is left to soak for 5 minutes, this is a helpful tool where multiple deer are being processed. But be aware that it only removes it from this type of surface, it does not neutralize or kill the prions.

It will be up to all of us to help slow the spread of the disease, as cervids around the world are important parts of the ecosystem, and significant losses of white-tailed deer, or any cervid, will negatively impact ecosystems and humans, who rely on the meat for food in many places, including Minnesota.

Here are some things you can do to help slow the spread of the disease.

  1. Stay informed, new information is being learned through research and the CWD regulations change from year to year.

  2. At this time there is no evidence that it poses a risk to humans. However, limiting our exposure to the prion is recommended by the CDC. You can limit exposure by not consuming meat from CWD positive animals, since the prion is not neutralized by heat or cold, cooking or freezing the meat is not known to make it safe. 

  3. In some zones testing is mandatory, but hunters should consider getting their deer tested even when it is not mandatory as it helps the DNR better manage the spread. The test involves taking samples of brain tissue and lymph nodes. Do not eat the meat until you get a “not detected” test result. Currently there is no available test for live deer.

  4. If you have your meat processed commercially, consider asking for it to be processed individually to avoid contact with meat that may not be known to be tested and found “not detected” for CWD.  Also, inquire about the health and safety procedures they use to ensure they are doing everything they can to protect your deer from accidental exposure during processing.

  5. Wear latex or rubber gloves while processing cervid meat, and minimize how much you handle organs, especially brain and spinal cord tissue, and avoid consuming these tissues.

  6. In some places feeding deer is prohibited because of known CWD cases, but it is important to consider not feeding deer at all. Where deer congregate in numbers, they have a greater chance of spreading disease.

  7. Avoid contact with deer that seem “friendly”. As with other wildlife, if they don’t have a good flight response to human presence it should not be interpreted as them being friendly, but that something could be wrong.

  8. If you know that CWD has been found in your area, please work with the DNR to help them manage the disease by cooperating with their efforts on private lands.

  9. If you see a deer that may be sick (see symptoms above) in Minnesota, please call 888-646-6367 to report the animal.

References

  • Chronic Wasting Disease. (n.d.). Retrieved from Centers for Disease Control and Prevention: cdc.gov/prions/cwd/prevention.html#:~:text=If%20you%20have%20your%20deer,eat%20meat%20from%20that%20animal

  • CWD background & resources. (n.d.). Retrieved from Minnesota Department of Natural Resource: .dnr.state.mn.us/cwd/about.html

  • Ingraham, C. (June, 2023 2). The cost of managing Minnesota’s deer: 33 million bucks. Retrieved from Minnesota Reformer: minnesotareformer.com/briefs/the-cost-of-managing-minnesotas-deer-33-million-bucks/#:~:text=The%20DNR%2C%20however%2C%20estimates%20that,seems%20like%20a%20reasonable%20investment.

  • Orenstein, W. (2023, May 8). In effort to curb chronic wasting disease, DFL lawmakers agree to ban new deer farms. Retrieved from n effort to curb chronic wasting disease, DFL lawmakers agree to ban new deer farms: minnpost.com/greater-minnesota/2023/05/in-effort-to-curb-chronic-wasting-disease-dfl-lawmakers-agree-to-ban-new-deer-farms/

  • Outreach, M. C. (n.d.). Chronic Wasting Disease- what can you do. Retrieved from Minnesota House of Representatives: house.mn.gov/comm/docs/7fea8c5d-8ec7-4efd-be58-b89bdb8f94ac.pdf