Chronic wasting disease, or CWD, is a neurological disease infecting wild white-tailed deer in Iowa and other members of the Cervidae family in North America including mule deer, elk, moose, and caribou. This page provides information on the current status of the disease in Iowa, references to learn more about the disease, and some simple recommendations everyone can follow to reduce the spread of the disease and ensure safe consumption of venison harvested in Iowa.
You can help by following these recommendations
- Don’t feed deer. Concentration of deer around artificial food or mineral sources can increase risk of transmission of the disease.
- In harvested deer, minimize contact with portions of the deer with the highest CWD possible concentrations (brain, lymph nodes, spinal cord, spleen) and safely dispose of carcasses where other deer will not contact them.
- Submit heads from deer harvested in or near CWD-positive areas for testing and discard meat from CWD-positive deer.
- Follow state laws regarding transportation and importation of deer, elk, moose, and caribou from areas with CWD.
- Captive facility operators should ensure wild deer have no interactions with captive herds.
- Report any deer that appears to be sick to local conservation officers.
Learn more about CWD
CWD is in the class of neurological diseases called transmissible spongiform encephalopathies (TSE), that infects hoofed mammals in the Cervidae family (cervids), including white-tailed deer, mule deer, elk, moose, and caribou. CWD is similar to other more well-known TSE diseases like bovine spongiform encephalopathy (mad cow disease) of cattle, scrapie of sheep and goats, and Creutzfeldt-Jakob Disease of humans. All these diseases are caused by an abnormally shaped class of proteins called prions, which cause microscopic holes to form in the brain, giving it a spongy appearance, and ultimately degrade neurological functions and cause death. All known TSE diseases are fatal, although some, including CWD, have delays between initial infection and display of symptoms and death.
CWD generally has prolonged incubation period, ranging from 16 months to 3 years, before the infected animal shows any symptoms. Once symptoms are expressed, they are consistent with those seen in many more common ailments of deer and are thus not individually diagnostic of CWD infection. A symptomatic CWD-positive deer will simply appear sick, with common symptoms including drooling, poor balance, or emaciation. However, healthy-appearing deer could also be infected with the disease and not be symptomatic. Only laboratory tests conducted by disease specialists can confirm CWD infection. Most laboratory tests are performed with samples of tissue from the brain or lymph nodes of a dead deer.
All known cases of CWD in wild deer have resulted in death of the afflicted animal shortly after symptoms become apparent. There is mixed evidence among white-tailed deer and other species (mule deer and elk) affected by CWD that infection can increased vulnerability to harvest or predation before succumbing to death by the disease. There is also some evidence to suggest that successful reproduction is reduced in infected deer. Research on genetic aspects of the disease has revealed that although there is genetic variation in susceptibility of some animals, there are no known genes that completely prevent infection, suggesting all animals are potentially vulnerable to contracting the disease.
Research has shown no strong evidence that CWD is transmissible to humans or cattle. However, due to the long incubation period of prion diseases, human populations at increased risk of exposure to potentially CWD-infected cervids are undergoing long-term monitoring to help understand what risk, if any, CWD poses. The Centers for Disease Control recommends avoiding eating meat from CWD-positive animals and using caution when handling CWD-positive carcasses.
Routes of transmission of CWD among deer
- Direct-transmission through bodily fluid exchange
- CWD can be transmitted from an infected deer to a healthy one through incidental exchange of bodily fluids, such as nasal discharge, saliva, urine, feces, or birthing matter. Likely routes of transmission include behaviors that bring deer into direct contact such as artificial feeding, interactions between bucks, or social interactions among family groups.
- Indirect transmission through contaminated soil
- Because CWD prions, the disease-causing agent, can persist in the soil, areas where bodily fluids of deer, such as saliva, urine, feces, or birthing matter, accumulate could serve as sources of infection. Such locations include concentrated feeding areas, scrapes, or other areas where deer gather.
|This map shows the current distribution of CWD in wild white-tailed deer in Iowa based on surveillance sampling by the Iowa Department of Natural Resources on hunter-harvested deer throughout the state since 2002.|
|This map from the U.S. Geological Survey shows the current distribution of CWD in wild and captive deer, elk, moose, and caribou in North America.|