Co-infection alters population dynamics of infectious disease.

Hanna Susi,Pedro F Vale,Anna-Liisa Laine,Benoit Barrès

doi:10.1038/ncomms6975

Abstract

Co-infections by multiple pathogen strains are common in the wild. Theory predicts co-infections to have major consequences for both within- and between-host disease dynamics, but data are currently scarce. Here, using common garden populations of Plantago lanceolata infected by two strains of the pathogen Podosphaera plantaginis, either singly or under co-infection, we find the highest disease prevalence in co-infected treatments both at the host genotype and population levels. A spore-trapping experiment demonstrates that co-infected hosts shed more transmission propagules than singly infected hosts, thereby explaining the observed change in epidemiological dynamics. Our experimental findings are confirmed in natural pathogen populations—more devastating epidemics were measured in populations with higher levels of co-infection. Jointly, our results confirm the predictions made by theoretical and experimental studies for the potential of co-infection to alter disease dynamics across a large host–pathogen metapopulation.

Highlights

Co-infections by multiple pathogen strains are common in the wild
We focused our study on the obligate fungal pathogen Podosphaera plantaginis naturally infecting the host plant Plantago lanceolata
Our study provides conclusive experimental evidence that withinhost disease dynamics change under co-infection resulting in an increase in between-host disease transmission

Summary

Introduction

Co-infections by multiple pathogen strains are common in the wild. Theory predicts co-infections to have major consequences for both within- and between-host disease dynamics, but data are currently scarce. Our results confirm the predictions made by theoretical and experimental studies for the potential of co-infection to alter disease dynamics across a large host–pathogen metapopulation. Empirical studies suggest that within-host competition and pathogen transmission are tightly linked, resulting in the potential for changed rates of disease transmission under co-infection[9,13]. The outcome of within-host co-infection may be mediated by the host’s responses to infection[15,16,17] Together these results suggest that co-infection is a potentially powerful driver of pathogen evolution and epidemiology. Local host populations support considerable diversity in their resistance[22], and understanding to what degree the dynamics of co-infection are mediated by the host is critical for understanding how general the changes in epidemiological dynamics in response to co-infection may be in the natural populations. Accounting for co-infection may be central for successful disease prevention efforts

Methods

Results

Conclusion