Current vaccines offer limited effectiveness and epizootics are common in farmed fish.
Development of broadly effective control measures require a more complete understanding of the interactions between pathogen and host factors that contribute to the disease state. We propose to identify additional mechanisms of virulence for A. salmonicida . Virulence determinants will be genetically and functionally characterized and assessed as possible vaccine candidates or as targets for alternative modes of therapeutic invention. If such an antibody response exists and if specific mutant analysis in salmon infection studies demonstrates that type IV pili are required for pathogenesis in vivo, the effectiveness of purified preparations of pilin as a vaccine will be determined. Alternatively, the pili may not invoke a substantive immune response but may still be important for productive infections.