On game farms, where cervids are concentrated in high numbers, one contaminated animal can quickly infect 80 percent of the herd. In a few localized hot zones in Colorado and Wyoming, where the disease has been present for decades, prevalence rates of 30 to 50 percent have been reported in wild herds.
Cervids have no natural immunity to CWD, and there is no treatment. Most researchers believe animals are contagious long before they develop noticeable symptoms. These may take years to show, but eventually all victims succumb to a pattern of staggering, shaking, and excessive salivation, thirst, and urination. This "night of the living deer" stage leads to death.