Host traits predict the transient disease dynamics that occur during the loss of an alternative host

The composition of host communities in host-pathogen systems is changing through the loss and introduction of host species. Prior studies have shown that these changes can increase or decrease disease levels. However, it remains unclear what transient dynamics occur while host community composition changes, and how the traits of added or lost hosts affect those disease dynamics. In this study, we analyze a two-host model with an environmentally transmitted pathogen, where infection prevalence (proportion of infected individuals) in the focal host species changes as the second (alternative) host species is lost from the system. We use global sensitivity analysis to determine which and when alternative host traits have the strongest effects on the focal host dynamics. We find focal host infection prevalence increased or decreased monotonically when the alternative host has sufficiently higher or lower abilities to spread disease, respectively, than the focal host, but can change nonmonotonically when hosts have similar abilities to spread disease and the alternative host is a sufficiently strong competitor. Additionally, we identify that the alternative host's shedding and uptake rates of pathogen propagules, birth rate, and interspecific competitive ability almost always have strong influence on the magnitude and rate of change in focal host infection prevalence. In contrast, The alternative host's transmission rate, recovery rate, and disease mortality rate are only strongly influential in limited circumstances. Our study yields insight into how host traits influence the transient disease dynamics that occur following host losses in multi-host communities.