title: Invasion ability and disease dynamics of environmentally growing opportunistic pathogens under outside-host competition.
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.
authors.affiliation: Department of Biosciences, University of Helsinki, Helsinki, Finland; National Institute for Health and Welfare, Helsinki, Finland.
authors.forename: Ilona
authors.initials: I
authors.lastname: Merikanto
authors.affiliation: Department of Biosciences, University of Helsinki, Helsinki, Finland; Centre of Excellence in Biological Interactions, University of Jyväskylä, Jyväskylä, Finland.
authors.forename: Jouni T
authors.initials: JT
authors.lastname: Laakso
authors.affiliation: Department of Biosciences, University of Helsinki, Helsinki, Finland.
authors.forename: Veijo
authors.initials: V
authors.lastname: Kaitala
mesh_terms: D000465:Algorithms; D054884:Host-Pathogen Interactions; D008962:Models, Theoretical; D009894:Opportunistic Infections / Q000453:epidemiology* / Q000382:microbiology / Q000469:parasitology