Abstract
Chronic wasting disease (CWD) is an always fatal, neurodegenerative prion disease of cervids. In North America, it affects white-tailed deer (Odocoileus virginianus), mule deer (Odocoileus hemionus), Rocky Mountain elk (Cervus elaphus nelsoni), moose (Alces alces shirasi), and reindeer/caribou (Rangifer tarandus). The disease spreads through direct contact with infected individuals or indirect contact with infectious material (e.g., fluids, feces, and tissues of infected animals). First recognized in Colorado in 1967, CWD has incessantly spread across North America having been detected in captive or free-ranging cervids in at least 30 states of the US, 4 Canadian provinces, Norway, Sweden, Finland, and South Korea. In free-ranging populations, uncontrolled CWD expansion leads to geographical spread, increased prevalence, reduced adult survival rates, and destabilization of population dynamics. While CWD has never been detected in California’s cervid populations despite surveillance efforts since 1999, the constant threat remains, as the disease could be introduced at any time through natural or anthropogenic movement of infected animals or materials. This study utilizes an agent-based modeling approach and integrates real mule deer population data, to simulate 5-year epidemiological expansion of hypothetical CWD introductions within the deer conservation units (DCUs) of California. Environmental factors such as wildfires and the presence of various scavenger species were also incorporated. Multiple scenarios were modeled, considering different deer densities and proposed management measures, including surveillance for initial detection, prompt response to the first detection, strategic harvest management, targeted culling, and carcass management. The model assesses the effectiveness of these management strategies, providing estimates of disease transmission probabilities, impacts on deer herds, and population dynamics for each DCU under various disease introduction scenarios. The model also quantifies the direct and indirect transmission events, as well as the probability of CWD infection across different deer populations. The findings contribute to evidence-based decision-making by providing valuable information to support the design of cost-effective surveillance and management strategies to better prevent and rapidly detect and control CWD in the case of a potential introduction in California.