Spatial effects in parasite induced marine diseases of immobile hosts

TL;DR

This paper develops a spatially-explicit individual-based model to study how parasite mobility influences disease spread in immobile marine hosts, revealing that higher mobility leads to more severe and faster epidemics.

Contribution

The study introduces a novel spatially-explicit model for marine disease transmission, including an analytical expression for the basic reproduction number considering spatial effects.

Findings

Higher parasite mobility results in increased infection numbers.

Greater mobility shortens epidemic duration.

The model predicts a transition from disease-free to widespread infection.

Abstract

Emerging marine infectious diseases pose a substantial threat to marine ecosystems and the conservation of their biodiversity. Compartmental models of epidemic transmission in marine sessile organisms, available only recently, are based on non-spatial descriptions in which space is homogenised and parasite mobility is not explicitly accounted for. However, in realistic scenarios epidemic transmission is conditioned by the spatial distribution of hosts and the parasites mobility patterns, calling for a explicit description of space. In this work we develop a spatially-explicit individual-based model to study disease transmission by waterborne parasites in sessile marine populations. We investigate the impact of spatial disease transmission through extensive numerical simulations and theoretical analysis. Specifically, the effects of parasite mobility into the epidemic threshold and the temporal progression of the epidemic are assessed. We show that larger values of pathogen mobility imply more severe epidemics, as the number of infections increases, and shorter time-scales to extinction. An analytical expression for the basic reproduction number of the spatial model is derived as function of the non-spatial counterpart, which characterises a transition between a disease-free and a propagation phase, in which the disease propagates over a large fraction of the system.