The rate at which parasite transmission occurs depends on several factors, including the rate of exposure to infective stages and susceptibility to infection. Measuring natural levels of exposure under field conditions can be especially challenging, partly because contact rates between host and infective stages can be highly heterogeneous. A further challenge is delineating the factors that drive heterogeneity in exposure. For a major class of parasites, transmission is intimately linked to the host’s feeding ecology; these trophically transmitted parasites rely on the ingestion of infective intermediate hosts by the definitive host for transmission. In this study, we test the hypothesis that heterogeneity in exposure to parasites is driven by variations in host feeding behavior. We combined epidemiological data and molecular analysis of host predation to investigate the link between host predation and parasite transmission in the white-footed mouse (Peromyscus leucopus) and its trophically transmitted parasite, Pterygodermatites peromysci, which utilized the camel cricket, Ceuthophilus pallidipes as the intermediate host.
Results/Conclusions
We found seasonal variation in the prevalence of infection in both definitive and intermediate host populations, which corresponded closely with temporal changes in the definitive host’s consumption of cricket intermediate hosts. Individual heterogeneity in cricket consumption was also associated with variation in parasite infection. Predation levels were higher among pregnant female mice than either non-pregnant but breeding females or non-breeding females. Correspondingly, pregnant females had a significantly higher prevalence of infection than other females. Taken together, these results suggest that higher rates of predation on intermediate hosts increase exposure to and infection by parasites. However, among male hosts the level of cricket consumption was not significantly different between breeding and non-breeding males; yet breeding males had a higher prevalence of infection than non-breeding males, suggesting that breeding males may be more susceptible to infection than non-breeding males. Overall, our study showed that heterogeneity in exposure to infection is driven by individual and seasonal variation in host feeding behavior. We discuss the implications of these heterogeneities on the transmission dynamics of parasites embedded in food webs, and the broader need to incorporate host feeding ecology into studies of infectious diseases.