Elk with Chronic Wasting Disease, Wyoming.
Photo credit: Dr. Elizabeth Williams, University of Wyoming. C/O CWD Alliance.
Chronic Wasting Disease (CWD) is a fatal, neurological disease of white-tailed deer, mule deer, elk, and moose. The disease was first recognized as a ‘wasting syndrome’ in mule deer in a research facility in Northern Colorado in 1967 and has since spread to free-ranging and captive populations in 23 US states and 2 Canadian Provinces. The disease is currently present in five of seven Kentucky-bordering states (Missouri, Illinois, Ohio, West Virginia, Virginia). Since 2002, KDFWR has tested over 25,000 deer and elk for CWD; all results have been negative. CWD has not been found in the State of Kentucky. To see which states have confirmed CWD in deer or elk, check out the US Geological Survey’s CWD Map.
CWD belongs to a group of diseases called Transmissible Spongiform Encephalopathies (TSE), which includes scrapie in sheep and goats, bovine spongiform encephalopathy (commonly known as "mad cow” disease) in cattle, and Creutzfeldt-Jakob disease in humans. It is suspected that the agent responsible for causing TSEs is an abnormal protein called a prion.
Although the exact method of transmission is unknown, evidence suggests that CWD is transmitted through direct animal-to-animal contact and indirectly through environmental contamination from feces, urine, saliva, and infected carcasses. There is evidence that CWD prions can survive in the environment even after infected animals have been removed.
Animals can be infected with CWD for months or years before clinical signs are evident. In the terminal stages of infection, deer and elk will show signs of progressive weight loss, excessive salivation and urination, increased water intake, and depression. Other noticeable changes include decreased interactions with other animals, listlessness, lowering of the head, blank facial expression, and repetitive walking in set patterns. In elk, hyper-excitability and nervousness may be observed. There is no known treatment for the disease and the disease is typically fatal.
NOTE: These signs are also symptomatic of other more commonly seen diseases, such as meningeal worm infections (“brain worm”) in elk and epizootic hemorrhagic disease or blue-tongue virus in white-tailed deer and elk.
No obvious lesions can be seen in affected animals. With advanced disease, the brain will have a “spongy” appearance when examined under a microscope.
The only definitive way to diagnose the disease is by examination of a portion of the brain stem (the obex) and lymph node tissue (the retropharyngeal lymph node). There is currently no practical live-animal test for chronic wasting disease.