Last year I wrote about chronic wasting disease’s (CWD) spread to deer populations in an increasing number of geographic areas in the U.S. Since then, the disease hasn’t stopped expanding its footprint. Every week bring reports of new CWD cases in areas it hasn’t been previously found in.

Deer, elk, and similar animals are the only species affected by chronic wasting disease. There’s no evidence that it can afflict livestock, other animals, or people. The concern with the disease therefore, is its effect on our wild deer and elk populations. If it spreads to cause significant death losses, there would be important implications for hunting seasons for these animals.

Chronic wasting disease is one of the “prion diseases.” These diseases are fascinating, confounding, and challenging. This is because prions are extremely resistant to degradation. CWD prions can live for months or maybe even years, out in the environment. (Contrast this with most animal viruses and bacteria, which die readily in sunlight or high temperatures.) This means that susceptible deer can become infected from their surroundings, not just contact with a CWD-infected animal. This presents big challenges for limiting disease spread.

Prion diseases affect the nervous system – the brain, spinal cord and nerves. The damage the prions inflict on the brain results in the long-term signs of the disease – behavior changes and a slow, progressive, fatal weight loss. As such, in an animal that’s died from, or infected with, CWD, the most infectious parts of the body are the brain and spinal cord.

To be sure, CWD prions can also spread between animals through saliva, urine, and droppings. But the brain and spinal cord of a deceased deer can harbor prions that could be infectious for months or years. When a CWD-infected deer dies in the wild, its body decomposes, but the prions don’t. Should deer come to graze and lick in that area – even months later – transmission could occur.

This aspect of CWD transmission brings me to my question. What did you do with your deer carcass after this year’s hunt? Notably, what happened to its head and backbone – and could that serve as a way that CWD could be spread – through our activity – to new areas?

The scenario would go something like this: a hunter bags a deer in South Dakota’s CWD-affected area (the four southwestern counties of the Black Hills). Despite being healthy-looking, the deer is infected with CWD. The hunter brings it back to his or her East River home, bones it out and tosses the remains of the carcass out in the shelter belt. A local deer comes by that carcass area, maybe even the next spring, and picks up enough infectious prion to become infected. And the disease spreads from there.

Fortunately, the chances of harvesting a CWD-affected deer, even in that part of the state, are still fairly low – and probably even much lower in other areas of South Dakota. Unless the deer is tested, we really don’t have a way of knowing. (As mentioned, CWD hasn’t been shown to affect people. It’s still best to avoid eating meat from a CWD-positive animal, out of an abundance of caution).

While other transmission routes are important, preventing the potential spread through carcass movement is something that every deer or elk hunter can help prevent. The best place for disposal of deer or elk carcass remains is an approved landfill. If you take your deer to a processor, or have a dumpster service at home, that’s taken care of. Our Game Fish and Parks department sponsors carcass

disposal sites, too. Proper disposal is a good habit for hunters everywhere, but especially important for those hunters bringing back animals from states or areas with higher CWD prevalence.

The spread of CWD is proving troublesome to halt. It will take the efforts of a lot of people, and maybe some future rule changes, to make sure it doesn’t march across our state. If you’re a hunter, or anyone interested in our wildlife populations, inform yourself about the disease, and understand that there are some steps you can personally take to prevent it from spreading.

Russ Daly, DVM, is the Extension veterinarian at South Dakota State University. He can be reached via e-mail at or at 605-688-5171.

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