The role host ecology plays in the evolutionary dynamics of parasitic pathogens pertaining to infectious diseases is not well understood, yet crucial from the perspective of (i) developing sound and comprehensive theories for pathogen evolution, and (ii) understanding the impact of changing host population structure on major infectious diseases. We develop a modeling framework that integrates mechanistic description of the within-host dynamics, between-host transmission, and the host population ecology to investigate evolutionary consequences. The evolutionary process is modeled by incorporating (i) selection based on pathogen's ability to infect susceptible hosts and its ability to avoid local extinction, and (ii) diversity that is maintained by introduction of random pathogen strains, mimicking mutation events. We study the evolution of acuteness and the duration of infection, when the between-host transmission and host population structure are subject to change.  

Results/Conclusions

The pathogen evolution is affected by both the transmission dynamics and the host ecology. While the shape of the transmission model determines the stability of derived optimum pathogen traits, the host ecology, on the other hand, affects the evolutionarily stable strategies (ESS) for pathogens. In patchier host populations, we find that pathogen's ability to out-compete other strains locally and its ability to proliferate across population patches can potentially select for different traits creating conflicting evolutionary pressures. The resulting ESS is dependent not only on epidemiological properties of the infection induced by the pathogen but also on the host ecology.