Beyond the Abiotic: Incorporating Symbiont-Pathogen Interactions into Studies of Virulence

Pamela James

Abstract

The host-symbiont relationship is complex and, in the case of pathogenic symbionts, can be devastating to host health. Attempts to analyze the variability in host-symbiont interactions have included the effects of abiotic factors such as salinity and temperature, but the influence of other symbionts of the same host is not often considered. Several examples demonstrate that symbionts also associated with the host can modify the host-pathogen dynamic. The bacterial endosymbiont Wolbachia confers resistance to viruses and malaria-causing protist parasites in their insect hosts. Wild bumblebees, whose populations have been negatively impacted by pathogens, have intestinal microbes that decrease trypanosome infection level. Intestinal bacterial symbionts can also increase the host’s susceptibility to infection, as is the case with intestinal virus infection and possibly some bacterial infections. These examples demonstrate that the interactions of all symbionts associated with the host need to be considered when studying the role of pathogens in host health.

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