Chronic wasting disease (CWD) is a prion disease of cervids characterized by clinical symptoms of progressive weight loss, abnormal behaviour and excessive salivation. Incidents have been reported in North America and Korea as well as in Europe. Current knowledge, based on in vitro
and in vivo
experiments, suggests direct CWD transmission to humans is unlikely. Nonetheless, humans may consume CWD-infected materials, which presents a potential risk. Studies indicate that transmission by horizontal infection of cervids probably occurs via
saliva, faeces, and urine as well as from environmental reservoirs of prions found in soil and water. In addition, infectivity in the skeletal muscle of infected deer has been observed. These findings suggest that direct contact with infected animals and indirect contact with prion-contaminated materials are potential sources of infection. However, recent studies on the detection of pregnancy-related prion infectivity imply the potential transmission of CWD from mother to offspring. In this chapter, fundamental aspects of CWD are reviewed.