Invasion Ability and Disease Dynamics of Environmentally Growing Opportunistic Pathogens under Outside-Host Competition |
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Authors: | Ilona Merikanto Jouni T. Laakso Veijo Kaitala |
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Affiliation: | 1. Department of Biosciences, University of Helsinki, Helsinki, Finland.; 2. National Institute for Health and Welfare, Helsinki, Finland.; 3. Centre of Excellence in Biological Interactions, University of Jyväskylä, Jyväskylä, Finland.; Louisiana State University, United States of America, |
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Abstract: | Most theories of the evolution of virulence concentrate on obligatory host-pathogen relationship. Yet, many pathogens replicate in the environment outside-host where they compete with non-pathogenic forms. Thus, replication and competition in the outside-host environment may have profound influence on the evolution of virulence and disease dynamics. These environmentally growing opportunistic pathogens are also a logical step towards obligatory pathogenicity. Efficient treatment methods against these diseases, such as columnaris disease in fishes, are lacking because of their opportunist nature. We present a novel epidemiological model in which replication and competition in the outside-host environment influences the invasion ability of a novel pathogen. We also analyze the long-term host-pathogen dynamics. Model parameterization is based on the columnaris disease, a bacterial fresh water fish disease that causes major losses in fish farms worldwide. Our model demonstrates that strong competition in the outside-host environment can prevent the invasion of a new environmentally growing opportunist pathogen and long-term disease outbreaks. |
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