Chronic Wasting Disease (CWD) Facts
What is Chronic Wasting Disease (CWD)?
Chronic Wasting Disease belongs to a family of diseases known as Transmissible Spongiform Encephalopathies (TSE) or prion diseases. Other TSEs include bovine spongiform encephalopathy (BSE) in cattle, scrapie in sheep, feline spongiform encephalopathy (FSE) in cats in Europe, and Creutzfeldt-Jakob disease (CJD) and a new variant (vCJD) in humans. While CWD is similar to BSE (“mad cow disease”), there is no evidence that CWD can be transmitted to people. CWD, which is 100% fatal with no known cure, is believed to be transmitted through prions, or misfolded proteins that attack the nervous system of the host. These prions accumulate in the brain, spinal cord, eyes, spleen, and lymph nodes of infected animals, but are found ubiquitously throughout the animal.
How does it spread?
CWD can spread through natural movements of infected animals, and transportation of infected animals or carcasses. Deer and other cervids may become infected with CWD by animal-to-animal contact or by animal contact with a contaminated environment. Prions are shed from infected animals in saliva, urine, blood, soft-antler material, feces, or from the decomposition of an infected animal which ultimately contaminates the soil and environment in which deer and other cervids live. Prions shed into the environment can remain capable of infecting other animals for many years. As more deer become infected over time the number of infectious CWD prions in the environment increases. Once CWD prions become established in an area, deer are more likely to become exposed to CWD by coming into contact with prions shed in the environment. Conversely, in areas where CWD is not well established, and where the environment is relatively uncontaminated, animal to animal contact is the most likely source of transmission of CWD to uninfected deer.
There are no known management strategies to mitigate the risk of indirect transmission of CWD once an environment has been contaminated with infectious prions. This makes eradication of CWD almost impossible in areas where CWD may have been established for a long period before initial detection. Removing infected animals from the population early in an outbreak offers some hope of limiting the geographic extent of the disease as well as prevalence within the deer population by reducing direct transmission between animals and limiting the potential for environmental contamination.
Where has it been found?
CWD has been detected in captive and free-ranging deer and elk in 21 states and two Canadian Provinces: Colorado, Wyoming, Saskatchewan, South Dakota, Nebraska, Montana, Wisconsin, New Mexico, Minnesota, Oklahoma, Illinois, Alberta, Utah, New York, West Virginia, Kansas, Michigan, Virginia, Missouri, North Dakota, Maryland, Iowa and Texas.
How can you tell if a deer has CWD?
The disease cannot be diagnosed by symptoms alone since some toxic and other neurologic afflictions can cause the animal to exhibit similar symptoms. A portion of the brain or lymph nodes found in the throat of an animal must be tested to confirm if the animal in question is infected with CWD. Unfortunately, there is no live-animal test to detect CWD. Symptoms of infected animals include: emaciation, excessive salivation, lack of muscle coordination, difficulty in swallowing, and excessive thirst and urination. Clinically-ill animals may have an exaggerated wide posture, may stagger and carry the head and ears lowered, and are often found consuming large amounts of water. However, as previously noted, these symptoms are similar to numerous toxic or neurological afflictions so diagnosis cannot be made by symptoms alone.
What should I do if I see a deer that shows symptoms of CWD?
Accurately document the location of the animal and immediately contact the nearest TPWD Wildlife Division or Law Enforcement Division office or call TPWD headquarters in Austin toll-free at (800) 892-1112 and enter 5 for wildlife and 1 for general wildlife information. Or contact TAHC toll-free at (800) 550-8242. Do not attempt to touch, disturb, kill or remove the animal.
Is CWD dangerous to humans?
Epidemiologists with the Federal Center for Disease Control and Prevention in Atlanta, Georgia, and along with the Colorado Department of Public Health and Environment, have studied CWD and have found no evidence that CWD poses a serious risk to humans or domestic animals. Years of monitoring in the affected area in Colorado has found no similar disease in people or cattle living there. The World Health Organization (WHO) has likewise advised that there is no current scientific evidence that CWD can infect humans. However, as a precaution, the WHO advises that no part of a deer or elk with evidence of CWD should be consumed by people or other animals.
What precautions should hunters take?
Health officials advise hunters not to consume meat from animals known to be, or believed to be, infected with CWD or any other disease. Since it’s not always apparent that a deer may be carrying a disease, hunters should take simple precautions such as wearing latex gloves when field dressing carcasses, and washing hands and instruments thoroughly with a 50/50 chlorine bleach and water mixture after field dressing is complete. Another precautionary recommendation is to bone out meat and avoid the central nervous system (e.g., brain and spine). Finally, when taking deer to a game processor, hunters may consider requesting their animals be processed individually, without meat from other animals being added to meat from your animal.
Can I have deer venison tested?
Deer “venison” cannot be tested; only brain and lymph node tissues can be tested to detect the presence of CWD. Texas Veterinary Medical Diagnostic Laboratory (TVMDL) can test appropriate samples for CWD at the owner’s expense. If you wish to have your harvested animal tested, please DO NOT freeze the head. The tissue sample must be removed soon after harvest. The entire head (it is acceptable to remove the antlers and the top of the skull) may be chilled overnight in a water-tight container and shipped to TVMDL. It is advisable to contact the lab (979-845-3414) before you send the sample. Arrangements can also be made through your local veterinarian to collect the appropriate tissue sample and store it in formalin. Once the sample is stored in formalin, it can be sent by regular post. TPWD biologists will be collecting tissue samples from hunter-harvested deer at meat processors and check stations located throughout the state.
What can hunters do?
Hunters should report any suspected cases of CWD to the TPWD or TAHC immediately. Proper disposal of carcasses is recommended for big game harvested in any area identified as a Containment Zone or High Risk Zone, in order to minimize the risk of spreading CWD via infected carcass parts to other areas of the state. Unused carcass parts could be disposed of at the site where the animal was harvested, in a landfill, or buried. Hunters should also support Texas surveillance efforts and should report any suspected movement or importation violations. Finally, hunters should become familiar with information about CWD as well as practical tips they may use in the field to help prevent spread of CWD and minimize any risks associated with the disease.
Where can I learn more?
- Texas Animal Health Commission: CWD
- Centers for Disease Control and Prevention: CWD
- Chronic Wasting Disease Alliance
- USGS National Wildlife Health Center: CWD