DOI: 10.5061/dryad.3tx95x6fz
title: Dose relationships can exacerbate, mute, or reverse the impact of heterospecific host density on infection prevalence

description: The likelihood an individual becomes infected depends on the community in
 which it is embedded. For environmentally transmitted parasites, host
 community composition can alter host density, the density of parasites
 that hosts encounter in the environment, and the dose to which hosts are
 subsequently exposed. While some multi-host theory incorporates some of
 these factors (e.g., competition among hosts), it does not currently
 consider the nonlinear relationships between parasite exposure dose and
 per-propagule infectivity (dose-infectivity relationships), between
 exposure dose and infected host mortality (dose-mortality relationships),
 and between exposure dose and parasite propagule excretion (dose-excretion
 relationships). This makes it difficult to predict the impact of host
 species on one another’s likelihood of infection. To understand the
 implications of these non-linear dose relationships for multi-host
 communities, we first performed a meta-analysis on published
 dose-infectivity experiments to quantify the proportion of accelerating,
 linear, or decelerating dose-infectivity relationships; we found that most
 experiments demonstrated decelerating dose-infectivity relationships. We
 then explored how dose-infectivity, dose-mortality, and dose-excretion
 relationships might alter the impact of heterospecific host density on
 infectious propagule density, infection prevalence, and density of a focal
 host using two host, one parasite models. We found that dose relationships
 either decreased the magnitude of the impact of heterospecific host
 density on propagule density and infection prevalence via negative
 feedback loops (decelerating dose-infectivity relationships, positive
 dose-mortality relationships, and negative dose-excretion relationships),
 or increased the magnitude of the impact of heterospecific host density on
 infection prevalence via positive feedback loops (accelerating
 dose-infectivity relationships and positive dose-excretion relationships).
 Further, positive dose-mortality relationships resulted in hosts that
 traditionally decrease disease (e.g. low-competence, strong competitors)
 increasing infection prevalence, and vice versa. Finally, we found that
 dose-relationships can create positive feedback loops that facilitate
 friendly competition (i.e., increased heterospecific density has a
 positive effect on focal host density because the reduction in disease
 outweighs the negative effects of interspecific competition). This
 suggests that without taking dose relationships into account, we may
 incorrectly predict the effect of heterospecific host interactions, and
 thus host community composition, on environmentally transmitted parasites.
description: This dataset contains two main pieces: First,
 we have collected studies that experimentally examined relationships
 between parasite/pathogen exposure dose and infec tion likelihood across a
 variety of taxonomic systems. We include code for analyzing data from
 these studies to quantify the relationship between dose and infection
 likelihood across these systems, useing a bayesian inference
 framework.  Second, we include code for conducting
 simulations where we explore the impact of dose-response relationships in
 disease dynamics in multi-host systems.
description: Instructions for using this dataset can be found in
 ReadMe_meta_analysis, ReadMe_simulation, and
 ReadMe_visualization.