Transmission mode impacts parasite spread in spatially structured environments

The spread of parasites and pathogens is shaped by their transmission to new hosts and often inherently linked to the spatial structure of host populations. Transmission modes are typically classified as either horizontal — between individuals — or vertical, from parent to offspring. While some parasites rely exclusively on one mode, many use both. We investigate how transmission mode impacts the spread of a parasite in different spatially structured metapopulations with variable habitat size and host dispersal propensity depending on infection status. We find that patch size disparities together with infection dependent dispersal result in local infection prevalence that deviates from single patch expectations, whereby the nature of this deviation differs depending on transmission mode. This work shows how parasite transmission mode alters infection spread through spatially structured environments and highlights that transmission modes can have distinct impacts on the evolution of host-parasite dynamics with potential consequences for disease management.