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Photograph by Joe Mac Hudspeth, Jr. · www.southernfocus.com

Magazine


Chronic Wasting Disease in Deer – What does this mean for Mississippians?

From the Spring 2018 issue

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Since February 9th, I don’t think a day has gone by when I haven’t thought about CWD and what is going to mean for Mississippi in the coming years. In some “CWD States” the disease has changed the deer herd, as well as hunting, while in other states, hunting appears to carry on without skipping a beat. What is the projected outcome for Mississippi?

First, a quick review of the disease. Chronic Wasting Disease (CWD) is a neurological disease that is fatal. CWD is categorized as a TSE disease, which stands for Transmissible Spongiform Encephalopathy – in English, this means holes develop in the brain – you can see why this is bad news for a deer. Mad Cow disease and Scrapie are examples of this TSE-type disease in other mammals. The actual agent that causes the disease is a little protein called a prion. These little prions can become abnormally shaped, and when they do, they cause the cells that typically produce normal prions, to instead make the abnormal prions. So prions are not a virus, or bacteria, they are a type of protein that all critters with a nervous system have in their body. Over time, the number of bad prions accumulate and cause the disease. This is why the “incubation time” for the disease can be months and over a year. The abnormal prions have to build up to a threshold amount before animal shows symptoms. It is at this time, when the deer is symptomatic of the disease, that it can shed these abnormal prions. The disease can be spread when an infected animal sheds the abnormal prions in their urine, feces, or saliva.

Where did the abnormal prions come from? We have only educated guesses at this point. Abnormal prions can live outside the body and can even be viable in the soil for years. We do know the deer found to have CWD was a native deer – meaning it’s genes corresponded to genes found in the Delta. Some scientists have hypothesized that abnormal prions are found in very small amounts all throughout the range of the white-tailed deer and deer have always suffered from CWD, we just didn’t know it. However, the vast majority of scientists that study CWD report that live animal transportation is the most efficient way to pass abnormal prions from place to place. This was very well documented with the movement of deer and elk from Colorado (where the disease was first discovered in deer) to other states and Canadian Provinces. Although live animal transportation could be the reason CWD found its way to Mississippi, we have no proof at this point.

So how will CWD impact deer in Mississippi? Will our deer herds decline? Will some deer herds go extinct? This is very, very unlikely. Because the disease takes months, and often years to manifest to a level for the deer to show symptoms, at which time its believed the deer shed the abnormal prions in the environment, deer can reproduce and keep building the population. Now this could be different in areas where a deer herd is struggling (where fawn production and/or adult survival are low) – in those places we would assume CWD could affect the deer herd more negatively. However, in most of Mississippi, this is not the case and we are fortunate to have great deer habitat and a productive herd. One thing to keep in mind, even with Mississippi’s productive deer herd, over time, the disease could cause the age structure to be younger simply because deer would not live to old ages. Because all deer that contract the disease will die, the number of animals living to ripe old ages will necessarily decrease.

We still have so much to learn before we can begin to make forecasts about how deer season will be affected in the fall of 2018. The Mississippi Department of Wildlife, Fisheries & Parks is executing their action plan and we need to support them and thank them for their efforts. Their plan involves sampling, potentially, a few hundred deer in the six-county area where the infected deer was found. As of the date of this article, well over one hundred deer have been sampled with no additional CWD-positive deer found. This is wonderful news for Mississippi! Some readers may be familiar with what occurred in Arkansas. When Arkansas Game and Fish Commission began sampling in their CWD positive zone in the northwest part of the state, they found over 20% of the deer had the disease. We are hoping the Mississippi experience will be like New York’s. When a CWD-positive was identified in New York the state wildlife agency rushed in and conducted their collections to assess the damage, but found very, very few deer had the disease. For the most part, CWD is no longer an issue in New York because it caught early.