Marina Voinson, Charles L. Nunn, Amy Goldberg

Parasites regularly switch into new host species, representing a disease burden and conservation risk to the hosts. The distribution of these parasites also gives insight into characteristics of ecological networks and genetic mechanisms of host-parasite interactions. Some parasites are shared across many species, whereas others tend to be restricted to hosts from a single species. Understanding the mechanisms producing this distribution of host specificity can enable more effective interventions and potentially identify genetic targets for vaccines or therapies. With increasing ecological connections to local animal populations, the risk to human health is increasing. Which of these parasites will fizzle out and which have potential to become widespread in humans? We consider the case of primate malarias, caused by Plasmodium parasites, to understand the interacting ecological and evolutionary mechanisms that put humans at risk for disease. Plasmodium host switching from primates to humans led to ancient introductions of the most common malaria-causing agents in humans today, and new parasite switching is a growing threat, especially in Asia and South America. Based on a wild host-Plasmodium occurrence database, we highlight geographic areas of concern and potential areas to target further sampling. Finally, we discuss methodological developments that will facilitate clinical and field-based interventions to improve human health based on this eco-evolutionary perspective.