Chronic wasting disease (CWD) is a fatal neurodegenerative disease of white-tailed deer (Odocoileus virginianus), mule deer (Odocoileus hemionus), Rocky Mountain elk (Cervus elaphus nelsoni), Shira’s moose (Alces alces sherasi), and reindeer (Rangifer tarandus). CWD is the most contagious transmissible spongiform encephalopathy and affects both free-ranging and captive cervids in predominantly North America. CWD is characterized by a prolonged course of individual infection, lengthy epizootics that last for decades, and delayed population impacts that occur after prevalence has reached a sufficient level. Geographic spread of new detections of CWD has increased dramatically since 2002, despite the disease having been present in North America since the 1960s.
The infectious agents of CWD are prions, mis-folded proteins that aggregates into beta-sheet rich amyloid deposits and affect nervous system function. CWD infection occurs through ingestion of infectious prions, which can be found in saliva, feces, blood and antler velvet of infected individuals. CWD can be transmitted to naïve cervids by direct contact with infected animals or through environmental reservoirs. Clinical signs include weight loss, anorexia, repetitive behaviors, hyperesthesia with progression to severe emaciation, severe behavioral changes, excessive thirst (polydipsia), excessive salivation, polyuria, tremors, and ataxia.
Current research is being conducted on CWD in Wisconsin white-tailed deer in collaboration with the Wisconsin Department of Natural Resources and USGS National Wildlife Health Center. Extensive information about this joint endeavor as well as additional information about CWD can be found on the project website and on the USGS NWHC website. The CWD Alliance maintains an extensive website on CWD news, scientific information, directory of experts, and many other resources related to CWD.
The guiding principles of CWD research activities being conducted by the USGS-Wisconsin Cooperative Wildlife Research Unit are to improve our scientific knowledge of CWD in free-ranging deer, and develop research to facilitate and refine CWD management actions. Our primary research objectives are aimed at providing reliable scientific information to inform chronic wasting disease management through an integrated approach to understanding:
- the impact of CWD on white-tailed deer survival rates,
- the population impacts of CWD for white-tailed deer,
- the spatial and temporal disease transmission of CWD in white-tailed deer,
- the role of movements and behavior for demographic and transmission processes,
- the role of genetics in disease dynamics, and
- forecasting for CWD management actions.
CWD may have long-term adverse population effects on these economically and ecologically valuable keystone species. Scientific understanding of the ecology and transmission of CWD in free-ranging wildlife is limited, but this information is critical to providing knowledge for making management decisions and helping to better understand the ecology of CWD in free-ranging populations.