Interactions among bacterial strains and fluke genotypes shape virulence of co-infection |
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Authors: | Katja-Riikka Louhi Lotta-Riina Sundberg Jukka Jokela Anssi Karvonen |
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Institution: | 1.Department of Biological and Environmental Science, University of Jyväskylä, PO Box 35, 40014, Jyväskylä, Finland;2.Centre of Excellence in Biological Interactions, University of Jyväskylä, PO Box 35, 40014, Jyväskylä, Finland;3.Eawag, Swiss Federal Institute of Aquatic Science and Technology, 8600 Dübendorf, Switzerland;4.ETH Zürich, Institute of Integrative Biology, 8092 Zürich, Switzerland |
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Abstract: | Most studies of virulence of infection focus on pairwise host–parasite interactions. However, hosts are almost universally co-infected by several parasite strains and/or genotypes of the same or different species. While theory predicts that co-infection favours more virulent parasite genotypes through intensified competition for host resources, knowledge of the effects of genotype by genotype (G × G) interactions between unrelated parasite species on virulence of co-infection is limited. Here, we tested such a relationship by challenging rainbow trout with replicated bacterial strains and fluke genotypes both singly and in all possible pairwise combinations. We found that virulence (host mortality) was higher in co-infections compared with single infections. Importantly, we also found that the overall virulence was dependent on the genetic identity of the co-infecting partners so that the outcome of co-infection could not be predicted from the respective virulence of single infections. Our results imply that G × G interactions among co-infecting parasites may significantly affect host health, add to variance in parasite fitness and thus influence evolutionary dynamics and ecology of disease in unexpected ways. |
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Keywords: | concomitant infection Diplostomum pseudospathaceum facilitation Flavobacterium columnare epidemiology multiple infection |
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