Species Interactions in a Parasite Community Drive Infection Risk in a Wildlife Population

TLDR

Hosts frequently carry multiple parasites, prompting the question of whether coinfection patterns arise from inter‑species effects or host‑specific differences. The study analyzed longitudinal data from individual hosts to quantify how co‑infecting parasites influence each other's infection risk, revealing strong positive and negative interactions. Even after controlling for host susceptibility and exposure, parasite‑community effects explain more variation in infection risk than host or environmental factors, highlighting the danger of misinterpreting data when parasites are studied in isolation.

Abstract

Most hosts, including humans, are simultaneously or sequentially infected with several parasites. A key question is whether patterns of coinfection arise because infection by one parasite species affects susceptibility to others or because of inherent differences between hosts. We used time-series data from individual hosts in natural populations to analyze patterns of infection risk for a microparasite community, detecting large positive and negative effects of other infections. Patterns remain once variations in host susceptibility and exposure are accounted for. Indeed, effects are typically of greater magnitude, and explain more variation in infection risk, than the effects associated with host and environmental factors more commonly considered in disease studies. We highlight the danger of mistaken inference when considering parasite species in isolation rather than parasite communities.