Testing epidemiological functional groups as predictors of avian haemosporidia patterns in southern Africa

Abstract

Understanding the dynamics of multihost parasites and the roles of different host species in parasite epidemiology requires consideration of the whole animal community. Host communities may be composed of hundreds of interacting species, making it necessary to simplify the problem. One approach to summarizing the host community in a way that is relevant to the epidemiology of the parasite is to group host species into epidemiological functional groups (EpiFGs). We used EpiFGs to test our understanding of avian malaria (Plasmodium and Haemoproteus) dynamics in four communities of wetland-associated birds in southern Africa. Bird counts and captures were undertaken every 2–4 months over 2 yr and malaria was diagnosed by nested PCR. One hundred and seventy-six bird species were allocated to a set of EpiFGs according to their assumed roles in introducing and maintaining the parasite in the system. Roles were quantified as relative risks from avian foraging, roosting, and movement ecology and assumed interaction with vector species. We compared our estimated a priori risks to empirical data from 3414 captured birds from four sites and 3485 half-hour point counts. After accounting for relative avian abundance, our risk estimates significantly correlated with the observed prevalence of Haemoproteus but not Plasmodium. Although avian roosting height (for both malarial genera) and movement ecology (for Plasmodium) separately influenced prevalence, host behavior alone was not sufficient to predict Plasmodium patterns in our communities. Host taxonomy and relative abundance were also important for this parasite. Although using EpiFGs enabled us to predict the infection patterns of only one genus of heamosporidia, our approach holds promise for examining the influence of host community composition on the transmission of vector-borne parasites and identifying gaps in our understanding of host–parasite interactions.