CalCWD: Simulating chronic wasting disease spread in California after the initial detection

Chronic Wasting Disease (CWD) is a prion-induced spongiform encephalopathy affecting cervids and leading to neurological deterioration and death. First detected in Colorado in the 1960s, it has since spread across North America, generating ecological and socio-economic impacts. Its recent detection in previously considered CWD-free California has increased the need for effective monitoring. This study applies CalCWD, an agent-based model simulating the spatiotemporal dynamics of CWD in California's mule deer populations. The model incorporates demography, social behavior, migrations, environmental conditions, and epidemiological dynamics using a SEIR framework, with transmission via within-group contact, environmental prions, and infectious carcasses. Simulations assessed spread risk over three years starting from detected cases in Inyo and Madera counties. Results indicate that the Inyo outbreak, likely affecting a migratory population, poses higher spread risk, while the Madera outbreak, likely involving a more resident population, spreads more slowly, with a mean spread velocity of 6.7 km/year. The model also identifies Benton and Mono valleys as potential pathways for the disease spread between California and Nevada, highlighting them as priority areas for increased surveillance. Overall, CalCWD provides valuable insight into CWD dynamics, serving as a supportive tool for monitoring and management, with potential application to other regions and cervid species.