Chronic wasting disease of cervids

Abstract

Chronic wasting disease (CWD) of cervids is the only known transmissible spongiform encephalopathy (TSE) found in non-domestic, free-ranging animals. To date, it is found in wild cervids only in North America, and natural infection has been detected in only four species (Cervus elaphus nelsoni, Odocoileus hemionus, Odocoileus virginianus and recently Alces alces) although there are concerns that it could spread to other species, particularly Rangifer tarandus. The infectious PrPCWD spreads throughout the body, particularly in lymphoid tissue, although lesions (typical of TSEs) are found only in the brain and are associated with development of clinical disease (e.g. wasting, behavioural changes). Transmission is lateral and probably oral. Infectious prions are shed in faeces, urine and saliva, and are present in various body tissues, all of which may contribute to ante- or post-mortem environmental contamination, increasing transmission. Infectious prions persist in soils. There is presently no evidence of spread to other sympatric wildlife, domestic livestock or humans. Intracerebral inoculation enables transmission to various species of ungulates, rodents, carnivores and even primates, but oral transmission to non-cervids has mainly been unsuccessful.