What is Chronic Wasting Disease?
A deer with Chronic Wasting Disease. Credit Terry Kreeger
Chronic Wasting Disease (CWD) is a highly-contagious neurological disease that infects deer, elk, and other cervids. It is similar to mad cow disease, scrapie that infects sheep, and Creutzfeldt-Jakob disease that affects humans. There is no known cure.
CWD causes the brain to degenerate, extreme weight loss, abnormal behavior, and then death. Infected animals can show no symptoms for years while still transmitting the disease throughout the herd.
The disease is caused by a misfolded protein called a prion that continues to multiply in the infected animal. Prions infect new animals through direct animal-to-animal contact, contact with feces, saliva, and carcass parts, as well as through environments (soil, etc.) contaminated with any of the above.
LISTEN >> Keep Tennessee CWD Free, An Expert’s View
Additionally, it is important to note that prions are neither viruses nor are they bacterium and are extremely difficult to destroy. In fact, once they get into the environment they can remain stable and infectious. Many in the wildlife science community believe that once they are established in an area, it is not realistic to ever remove them from the wild environment.
While there have been no known cases of transmission to humans at this time, recent research has produced conflicting results about transmission to primates. A 13-year-long study by the National Institutes of Health showed no trace of CWD within primates after they were exposed to the prion, including through food. A 3-year Canadian study showed CWD crossing the species barrier to infect primates. However, the Canadian results are preliminary and have not been published, so its methodology and accuracy have not been assessed by the scientific community.
You will likely never see an animal showing symptoms of CWD. Symptoms only appear long after infection and the unhealthy animal is often first killed by predators, vehicles, or other diseases.
According to the CWD Alliance, CWD has been confirmed in 25 states, including our neighbors Arkansas, Mississippi, Missouri, and Virginia.
For more information about CWD, visit the CWD Alliance at cwd-info.org
Is Chronic Wasting Disease the same as Epizootic Hemorrhagic Disease (EHD) or Bluetongue?
No. Chronic Wasting Disease is a contagious disease with no known cure that has the potential to decimate wild deer populations.
Epizootic hemorrhagic disease (EHD) and bluetongue, while both contagious, are two separate types of viral hemorrhagic disease that can cause short-term declines in localized cervid populations, but do not seem to have any significant effect on long-term herd health and survival.
Both EHD and bluetongue do cause a significant reduction in the physical health and appearance of deer (i.e., wasting) and ulceration, particularly of the mouth and tongue.
Because the viruses are transmitted by biting insects, such as midges, the disease comes and goes with the seasons. Additionally, some deer do survive EHD and bluetongue and are able to pass along immunity to their offspring. This is not the case with CWD as it is always fatal.
What does deer farming have to do with Chronic Wasting Disease?
Captive Deer by Dr. Terry Kreeger
Deer farming creates high-density populations of deer, making it an ideal environment for transmitting CWD. While deer farms are fenced, escapes of captive deer and elk occur when fences are damaged by storms. Deer farms also regularly transport deer across state lines, which appears to serve as a method by which CWD can be established in other captive and potentially wild deer herds. In Tennessee, it is illegal to farm native deer species, with the exception of elk, which may be farmed under certain circumstances.
For these reasons, among others, the Federation opposes deer farming in our state.
Is controlling CWD an option?
In short, no. Preventing CWD from entering an area is really the only effective means of controlling the disease. The prion is extremely resistant to control mechanisms and, to date, no method has successfully destroyed the prion and eradicated the disease from infected areas.
Further, once CWD is introduced to an area, attempts to contain the disease—including monitoring herds, testing deer, culling herds, containing infected populations, and enforcing strict carcass disposal and importation rules—are both extremely costly and controversial.
Why does Chronic Wasting Disease matter to me?
Father and daughter with a CWD free doe at a Federation youth deer hunt in West Tennessee
Chronic wasting disease is a serious threat to Tennessee’s deer population along with the food, traditions, and conservation funding it provides.
For example, in Wyoming wildlife biologists estimate a 10 to 20 percent decrease in its mule deer population each year because of CWD. In parts of southern Wisconsin, the infection rate has been measured between 30 to 50 percent of the deer sampled, with bucks seemingly more susceptible to CWD than does. Because CWD is always fatal, we know that parts of Wisconsin will lose at least half of its deer herd. This means if the disease is ever established in Tennessee, it is not unreasonable to say that it could greatly reduce hunting opportunities and the chance for new hunters to carry forward an important piece of American culture.
Currently, CWD is not thought to be transmittable to humans, but it is recommended that venison from a CWD-positive deer, or any deer showing signs of illness, be disposed of—not consumed. This could eliminate an important source of food for many Tennesseans, while also removing an incentive to get out and hunt. The U.S. Centers for Disease Control and Prevention has issued this article about the potential of transmission of CWD to humans.
Because of these factors, states with CWD often see a drop in the number of deer hunters–the largest group of hunters in Tennessee. Money from sporting licenses and a special tax on firearms and ammunition fund a large portion of all wildlife conservation in Tennessee. And hunters are eight times more likely to support public conservation policies. Without these hunters, all wildlife conservation will suffer.
If CWD comes to Tennessee, much more than the deer population will be hurt.
What can I do to Keep Tennessee CWD Free?
There are several measures Tennesseans can take to keep Tennessee CWD free.
First and foremost, Tennessee law prevents importation, transportation, or possession of deer or other cervid carcasses from any area where there has been a known case of CWD. More information about this restriction is available here: www.tn.gov/twra/hunting/cwd.html
Additionally, Tennesseans can minimize the risk of CWD by taking these simple precautions.
- Do not transport animals or carcasses. Before bringing an animal product into Tennessee, it must meet minimum processing standards. Always consult current Tennessee Wildlife Resources Agency guidelines.
- Follow recommendations for disposal of the carcass and tissues of infected animals.
- Field dress and bury the offal and tissues of harvested animals. Or, field dress and double bag the offal and tissue for disposal in a landfill. Use rubber or latex gloves.
- Do not bait or feed game. In Tennessee, baiting game is illegal. The risk of CWD makes it even more important to avoid this practice. Baiting game attracts deer, thereby artificially increasing the deer population in a small area, increasing opportunities for the disease to be transmitted.
- Avoid use of urine products. While it is not a known pathway for infection, urine has been shown to contain the prion that causes CWD. Additionally, it can also attract more animals to a smaller space, increasing opportunities for infection.
- Report to TWRA any animal that appears to be acting abnormally or appears to be sick. If you harvest an animal that you suspect may be ill, request testing and share results with TWRA.
It is imperative to follow all regulations, restrictions, and recommendations issued by regulatory agencies, such as TWRA and the Centers for Disease Control.
For more information about CWD prevention, listen to this audio recording and visit cwd-info.org
It is our responsibility to keep Tennessee CWD free.