Dose relationships can exacerbate, mute, or reverse the impact of heterospecific host density on infection prevalence

The likelihood an individual becomes infected depends on the community in which it is embedded. For environmentally transmitted parasites, host composition can alter density, density of parasites that hosts encounter environment, and dose to are subsequently exposed. While some multi-host theory incorporates these factors (e.g., competition among hosts), does not currently consider nonlinear relationships between parasite exposure per-propagule infectivity (dose–infectivity relationships), mortality (dose–mortality propagule excretion (dose–excretion relationships). This makes difficult predict impact species one another’s infection. To understand implications for communities, we first performed a meta-analysis published dose–infectivity experiments quantify proportion accelerating, linear, or decelerating relationships; found most demonstrated relationships. We then explored how dose–infectivity, dose–mortality, dose–excretion might heterospecific infectious infection prevalence, focal using two-host, one-parasite models. either decreased magnitude prevalence via negative feedback loops (decelerating relationships, positive dose–mortality increased (accelerating Further, resulted traditionally decrease disease low competence, strong competitors) increasing vice versa. Finally, create facilitate friendly (i.e., has effect because reduction outweighs effects interspecific competition). suggests without taking into account, may incorrectly interactions, thus composition, parasites.