By: John M. Tomeček
What is Chronic Wasting Disease (CWD)?
CWD is a disease that affects the nervous system in some cervids including white-tailed deer, mule deer, red deer, elk, sika deer, reindeer, and moose. The precise origins of CWD are unknown. The condition was first detected in 1967 in a research mule deer herd in Colorado. Today it is present in 24 US states and 2 Canadian provinces. Chronic Wasting Disease is one in a group of diseases called the transmissible spongiform encephalopathies (TSEs), such as scrapie in domestic sheep and goats, and bovine spongiform encephalopathy (BSE) in cattle. CWD is not thought to be transmitted to humans or livestock. It is caused by a type of misfolded protein (prions) which causes host animals to replicate the misfolded protein. Prions interrupt and degrade nerve cells and ultimately eliminate basic nervous system functions, leading to death.
What are the symptoms?
Symptoms appear from 16 to 36 months after infection. These include:
◆ Emaciation or generally poor body condition
◆ Decreased activity and/or erratic behavior
◆ Wide, low stances and blank expressions
◆ Excessive drinking and urination
◆ Salivation and grinding of teeth
◆ Keeping distance from the herd
◆ Loss of fear of humans
Because these symptoms are common to a number of diseases, positive diagnosis requires laboratory testing by a trained professional.
How is it spread?
Chronic Wasting Disease is spread among susceptible animals by direct and indirect contact with infected tissue and body fluids including saliva, urine, feces, or an infected carcass. These prion carrying sources are deposited on the ground and in the soil, and can be picked up by other animals during foraging. Research indicates that some plants and soil types bind prions. Other inanimate objects like feeders, water containers and possibly rubs and scrapes have been experimentally implicated in CWD transmission. Thus, reservoirs of prions in the environment enable transmission. Prions are capable of persisting in the environment for long periods of time. Though motheroffspring transmission is possible, lateral transmission between two animals is thought to be the typical route for infection, primarily by ingestion or inhalation.
Can CWD affect livestock or humans?
There is no strong evidence that CWD is transmissible to humans or domestic livestock. However the CDC and WHO advise that animals known to be infected with a prion disease should not enter the food chain to be consumed by humans or livestock. If hunting in a known CWD area, it is strongly advised to test your harvest and not consume it until the results are complete. Prions accumulate densely in the brain, spinal cord, other nervous tissue, eyes, tonsils, spleen, and lymph nodes of infected animals. These tissues should never be consumed and good personal protection practices such as wearing disposable gloves while field dressing is encouraged. In areas affected by CWD, bone out carcasses in a way that removes all nervous system tissue. Be sure not to cut meat with saws or knives that were used to cut bone. To prevent exposing other susceptible animals to infected material, bury the inedible carcass parts as deeply as possible or dispose of it in an approved landfill.
What should I do if I see an animal that might have CWD?
- Immediately contact the nearest Texas Parks and Wildlife Department (TPWD) Game Warden or Wildlife Biologist or the Texas Animal Health Commission (TAHC).
- If directed to send a sample for testing by TPWD or TAHC, contact your local TPWD biologist for professional assistance in collecting the sample.
- Follow any instructions given by those agencies for follow-up.
What are the recommended treatment and prevention strategies for CWD?
There is no vaccine to prevent infection and, once infected, there are no effective treatments. Although researchers are working to develop such tools, the way to prevent the spread of CWD, for now, is to manage susceptible animal populations.
The best management practices are to:
(1) restrict movement of live animals,
(2) restrict movement of potentially infected carcass parts,
(3) manage populations to keep deer densities at or below carrying capacity, and
(4) minimizing animal to animal contact at areas like feeding stations.
How can I help?
The best way to help is to be vigilant and carefully follow any requests or regulations from Texas Parks and Wildlife or the Texas Animal Health Commission. Preventing CWD provides the best chance to minimizing the spread of the disease. Encourage fellow Texans to remain calm, and work to prevent the spread of misinformation. The resources below provide detailed, factual information on CWD.
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