Chronic wasting disease is a neurological disease that is caused by abnormally folded isoform of the cellular prion protein. It’s is a naturally occurring transmissible spongiform encephalopathy (TSE) affecting members of the cervid species2. Its much like mad cow disease in cattle or Scrapie in sheep, the abnormal prion cause death in brain cell and affect the central nervous system, which ultimately kills its host.
Chronic wasting disease was first identified in closed captive mule deer in Colorado State University in 1967. Originally CWD only affected the captive mule deer around Colorado area, but soon spread to free ranging moose and white-tailed deer and 19 other states and the Republic of Korea. This geographic distribution of CWD is caused by two factors: the slow proliferation of disease of free-range cervid population and the transmission of disease within the captive herd.
Current reports and data of the pathogenesis of the chronic wasting disease in the natural host are predicted fromScrapie in sheep, because both show great similarity in its mode of transmission. CWD prion can transmit through direct and indirect contact in nature. The infected cervid species can infect a susceptible species through bodily fluid and bodily tissue. There is also report of high rate of maternal-to-offspring transmission of CWD prions, regardless of gestational period in Rocky Mountain elk. Environmental transmissions are also possible, because prion can still survive outside of the host, so it can infect a susceptible species through contact of urine, feces, bodily fluid, and even decomposed crops. The infectious CWD prion past through digestive system from ingesting contaminated material in nature. Then it quickly travels to the lymphoid of the host, and lymphoid will later direct the prion to the central nervous system and proliferates. The prion can accumulate in multiple tissues along the CNS, glands, kidney, and etc.
Management of chronic wasting disease has different approaches depending on the objective. To sufficiently management and control the CWD, we must target two populations: the farmed cervid and the free-ranging cervid. Wesurveillance the CWD in farm cervid by an individual animal identification combine with a herd certification approach. Upon identification of a positive case, herds are placed under quarantine prior to depopulation with or without indemnity; animals are then traced back to identify herd origin and tested for CWD. CWD control with free-range cervid is much more problematic compared to farmed cervid due to large population of infect cervid combined with great land mass. There is some success in managing the free-range cervid by nonspecific culling by government-sponsored sharpshooters. This reduces the infected cervid population in the wild and reduces contaminated materials.
(1)Haley, N. J., & Hoover, E. A. (2015). Chronic Wasting Disease of Cervids: Current Knowledge and Future Perspectives. Annual Review of Animal Biosciences,3(1), 305-325. doi:10.1146/annurev-animal-022114-111001