CWD in Tennessee

The 2022-2023 deer hunting season will mark the fourth full deer hunting season since the discovery of chronic wasting disease (CWD) in southwest Tennessee. We may never know how or when CWD was introduced into Tennessee, however, it is clear that CWD is established in Fayette and Hardeman counties. Furthermore, the disease will always be present there at some level. TWRA remains committed to preventing the spread of CWD throughout Tennessee and striving to decrease the prevalence of the disease where it is known to exist.

The Disease At A Glance

CWD is a transmissible spongiform encephalopathy found in deer, caribou, elk, and moose. It was first recognized as a syndrome affecting mule deer by researchers in Colorado in the late 1960s. It was not until the early 1980s that the cause of CWD was identified as an infectious abnormal protein called a prion. Prions, the unique infectious agent that causes CWD, are a challenge to manage for many reasons, including:

• Prions are not living organisms.
• Prions are extremely difficult to destroy (both in the body and outside of the body).
• Prions can be found all throughout the body and in most tissues, fluids, and excretions.
• Prions accumulate in the highest amount in the brain and spinal cord, which leads to the symptoms seen in sick animals.
• Once infected, animals may not begin to show clinical signs for up to 18 months.
• Once an infected animal begins to show signs of CWD, they may live for many months.
• Although prions do not reproduce outside of a living host, they may remain infectious indefinitely once in the environment.
• Direct and indirect transmission occurs.
• Prion infections are always fatal: mortality rate is 100%.
• No vaccines or treatment for prion infections currently exist.
• There are no known cases of CWD in humans.

Unfortunately, CWD is not easy to diagnose on the hoof. Infected deer often appear seemingly healthy and in good body condition until the very late stages of the disease. The buck pictured here appeared healthy when it was harvested, but upon testing for CWD, the results showed that it was in fact positive for CWD. Furthermore, older bucks are more likely to be detected with the disease. Although all age and sex classes have the potential to be infected with CWD, in Tennessee’s white-tailed deer populations adult bucks have twice the disease prevalence when compared to adult does.

Surveillance and Monitoring Efforts 2018-2022

Since 2018, TWRA has implemented a robust and far-reaching surveillance program designed

to detect new CWD infections across the state and to monitor changes in prevalence where the disease is already found. These goals were only met because of the continued support of hunters and industry partners. TWRA has tested over 54,000 free-ranging white-tailed deer and elk through the statewide surveillance program. Surveillance goals were successfully met in every Tennessee county over the last four years. Over 1,900 deer have tested positive for CWD, with all of them being located in west Tennessee. To date, CWD has been detected in fourteen counties (Chester, Crockett, Fayette, Gibson, Hardeman, Hardin, Haywood, Henry, Lauderdale, Madison, McNairy, Shelby, Tipton, and Weakley). Five additional counties (Carrol, Decatur, Dyer, Henderson, and Wayne) have been classified as high risk due to the detection of CWD within 10 miles of the county line. Most samples are collected during hunting season as part of a massive statewide effort, but samples are also collected from road-kills and from sick and dying animals throughout the year. Samples are collected through a network of voluntary hunter submissions, assistance from taxidermists and processors, and TWRA sponsored check stations.

After the 2021-2022 deer hunting season, Fayette County had the highest county-wide prevalence of CWD at 17.7% and Hardeman County had the next highest at 11.8%. Both Fayette County and Hardeman County have seen significant increases in prevalence since 2018. Within these two high-prevalence counties, the disease is not distributed evenly, and the prevalence essentially represents an average for the county.

Roughly 60% of the known positive deer come from an area centered on the southern half of the Fayette-Hardeman County line. CWD prevalence is higher in and around this core area than in other parts of these counties. A much lower percentage of deer that are harvested from other areas of Fayette and Hardeman counties test positive for CWD. The remaining counties where CWD has been detected all have prevalence below 2% and range from 1.5% (Shelby) to 0.1% (Henry).

Although it may seem as if the disease has spread rapidly across southwest Tennessee, the reality is the disease was likely there for many years before being detected. It has taken fouryears of surveillance to fully understand the extent of the affected area. It is critical that we swiftly and effectively employ our management. If left unchecked, the disease mayyet continue to spread past the known range in Tennessee.

CWD Management in Tennessee

Best management practices for CWD involve a multipronged approach to not only prevent the disease in different deer groups (i.e., reducing the geographic spread and prevalence), but also to address the environmental persistence of prions as a source of infection. At this time, there are no practical means of removing, inactivating, or mitigating prions in the environment, which leaves the focus of management on limiting deer interactions and human assisted movement of prions. Much like managing wild deer populations, CWD management is only successful as a collaborative effort between the Agency and its stakeholders (e.g., hunters, landowners, etc.). It is a balancing act between meeting disease management objectives and maintaining a viable and sustainable population. Current programs are aimed at increasing hunter participation through increased bag limits and harvest opportunities, engaging landowners in active CWD management, focusing additional removal of deer around confirmed positives in low prevalence areas, and conducting annual aerial surveys to monitor the effects of CWD on population levels. In addition, regulations help prevent the spread of prions by humans. Current CWD-specific regulations restrict the movement of live deer in the state, restrict the movement of infected carcasses outside of known CWD endemic areas, and prohibit practices that concentrate deer.

Future of CWD in Tennessee

The long-term impacts of CWD on deer populations in Tennessee are currently unknown. Other states battling CWD have documented deer population declines above 40% in locations where the disease is present. Other states have seen a shift in the age structure—meaning they no longer see older deer. These outcomes are neither desirable, nor consistent with managing for long-term, healthy, and sustainable deer populations. TWRA is committed to preventing these undesirable outcomes. TWRA is actively pursuing collaborations for research projects to improve the detection of CWD in field settings. One such project is using dogs as biosensors (i.e., detectors) of active infection in wild animals. Additionally, research is being conducted to better understand the role environmental deposits of prions play in the natural disease transmission cycle. TWRA is committed to learning more about CWD disease dynamics through disease surveillance and monitoring programs. TWRA needs active input from our stakeholders and strives to provide them with the most up-to-date developments. CWD management programs in Tennessee are constantly being refined in response to new research and changing conditions across the landscape. TWRA is currently developing a long-term CWD Management Strategic Plan to provide a framework for prevention, surveillance, monitoring, management, and research activities.

CWD management is not a one-man band. It is a partnership between TWRA, partners, hunters, landowners, and you. Your engagement and support are needed. Please, harvest more deer in Unit CWD. Abide by carcass transportation and feeding restrictions in CWD-positive and high-risk counties. Read all of the CWD content in this hunting guide and at CWDinTN.com. Seek out credible sources and understand the newest scientific information on CWD management. Signup for email updates at CWDinTN.com. Together we can conserve a healthy deer population for the benefit of present and future generations.