Chronic wasting disease in mule deer: disease dynamics and control

We developed a mechanistic model to simulate dynamics of chronic wasting disease (CWD) in mule deer (Odocoileus hemionus) populations. The model projected age-specific disease dynamics, changes in population size, and effects of control strategies. We estimated parameters front observations of infected and uninfected mule deer in Colorado. We used Monte Carlo techniques to evaluate likely responses. Simulations of CWD epidemics were highly unstable. Disease was nor sustained in projected populations when transmission rates were low, but CWD eliminated populations when more realistic transmission rates were used. We failed to produce stable coexistence of CWD in simulated mule deer populations. Even low CWD prevalence reduced potential harvest via combined effects of diminished per-capita production and decreased population density, Changes in CWD prevalence within populations were highly sensitive to transmission rate, and small decreases resulted in noticeable damping of prevalence increases. Simulated selective culling programs revealed the importance of initiating control while CWD prevalence was low (<0.01). Low selective culling rates (<20% of infected populations) effectively eliminated CWD if initiated when prevalence was low, but the likelihood of control diminished rapidly as prevalence increased. Management programs will likely require an effort sustained over many decades if eliminating CWD is the desired goal.