Chronic Wasting Disease (CWD)
Chronic Wasting Disease (CWD) is a severe and invariably fatal neurological condition that primarily affects cervid species, such as deer, elk, caribou, and moose. It was initially identified in mule deer at a Colorado research facility in 1967. CWD belongs to the transmissible spongiform encephalopathy (TSE) family of diseases, which includes notable diseases like Bovine Spongiform Encephalopathy (BSE or Mad Cow Disease) in cattle, Creutzfeldt-Jakob disease (CJD) in humans, and Scrapie in sheep and goats.
Mechanism of CWD
CWD is characterized by the presence of infectious prions, which are abnormal proteins that induce the misfolding of normal prion proteins in the brain. This misfolding triggers a chain reaction, resulting in the formation of sponge-like holes in the brain tissue.
CWD can spread through both direct and indirect means. Direct transmission occurs through animal-to-animal contact, while indirect transmission can happen via prion-contaminated environments. Infected animals shed infectious prions through their saliva, urine, and feces. Additionally, the carcass of an infected animal can contribute to environmental contamination, allowing the prions to remain infectious for extended periods.
Animals infected with CWD may not exhibit clinical signs of the disease for up to 18 to 24 months after infection. During this incubation period, they may appear healthy but remain infectious, contributing to disease spread. In the late stages of CWD, clinical signs become more evident and include lowered head and ears, progressive weight loss, a rough hair coat, excessive salivation, increased thirst and urination, and various behavioral changes, such as stumbling and a lack of fear of humans. However, most animals infected with CWD are more likely to succumb to other causes before reaching this late stage.
CWD poses significant concerns for wildlife management and conservation efforts, as its prevalence can impact cervid populations and ecosystem dynamics. Additionally, there are concerns about potential zoonotic transmission, where CWD could jump to humans, although such cases have been rare and the risk remains a subject of ongoing research.