Chronic Wasting Disease Exposure Risk to Male Cervids During the Mating Season in A Multi-Host Community

Multi-host infectious diseases present myriad challenges to wildlife managers due to variation in spatial overlap, contact rates, and host competence that complicate understanding of exposure risk and transmission dynamics. These challenges are present in cervid systems impacted by chronic wasting disease (CWD), where CWD prevalence tends to be highest in male cervids. This study focuses on male cervids during the mating season in a multi-host system where CWD is enzootic. We used wildlife camera traps placed at two types of potential local infectious zones-water tanks and scrape sites-and reference sites to measure spatial overlap and duration of contact behaviors for three susceptible cervid species: mule deer (Odocoileus hemionus); white-tailed deer (Odocoileus virginianus); and elk (Cervus canadensis). For each species, we evaluated differences in intraspecific, interspecific, and total environmental exposure risk, along with direct exposure risk, at each site type. We also explored how varied assumptions of host competence across species affected interspecific exposure risk. For mule deer and white-tailed deer, interspecific environmental exposure risk was 100 and 6 times higher at local infectious zones than at reference sites, and exclusively occurred at water tanks for elk. Interspecific environmental exposure risk occurred entirely at local infectious zones, but the proportion of total risk attributed to intraspecific vs. interspecific contributions depended greatly on whether we considered mule deer and elk to have equal host competence or used prevalence within a species as a proxy for variable host competence. Mule deer engaged in direct contact behaviors for similar durations across all site types, with no significant differences in direct exposure risk across sites. Our study highlights the potential central role of mule deer in multi-host cervid communities impacted by diseases transmitted horizontally such as CWD, and provides insight for CWD surveillance and management during a period of particularly high male-male contact that is relevant to CWD epidemiology.