title: Co-infection alters population dynamics of infectious disease.
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.
authors.affiliation: Metapopulation Research Group, Department of Biosciences, University of Helsinki, PO Box 65 (Viikinkaari 1), Helsinki FI-00014, Finland.
authors.forename: Hanna
authors.initials: H
authors.lastname: Susi
authors.affiliation: Metapopulation Research Group, Department of Biosciences, University of Helsinki, PO Box 65 (Viikinkaari 1), Helsinki FI-00014, Finland.
authors.forename: Benoit
authors.initials: B
authors.lastname: Barrès
authors.affiliation: 1] Centre for Immunity, Infection and Evolution, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3FL, UK [2] Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3FL, UK.
authors.forename: Pedro F
authors.initials: PF
authors.lastname: Vale
authors.affiliation: Metapopulation Research Group, Department of Biosciences, University of Helsinki, PO Box 65 (Viikinkaari 1), Helsinki FI-00014, Finland.
authors.forename: Anna-Liisa
authors.initials: AL
authors.lastname: Laine
mesh_terms: D001203:Ascomycota / Q000502:physiology*; D001499:Bayes Theorem; D060085:Coinfection / Q000382:microbiology*; D003141:Communicable Diseases / Q000382:microbiology*; D054884:Host-Pathogen Interactions; D016014:Linear Models; D010641:Phenotype; D010935:Plant Diseases / Q000382:microbiology* / Q000706:statistics & numerical data; D010943:Plantago / Q000382:microbiology*; D011157:Population Dynamics; D013172:Spores, Fungal / Q000502:physiology