Introductory studies on bacterial agents infecting cleaner fish

Cleaner fish (wrasse and lumpsucker) are used extensively in Norwegian salmon farms for biocontrol of sea louse infestation, but cleaner fish health and welfare has only recently become a focus of attention. Bacterial diseases represent one of the main threats to the sustained use of cleaner fish, and atypical Aeromonas salmonicida and Vibrio splendidusrelated strains remain the most commonly isolated bacterial agents in this regard. While A. salmonicida is an established fish pathogen, the relevance of V. splendidus for fish disease is less clear. Development of vaccines against bacterial pathogens of cleaner fish may be needed, but more knowledge is required regarding strains associated with these fish. In the present study, which focused mainly on wrasse, we examined bacterial infection levels in cleaner fish before and after salmon cage stocking, by culture and A. salmonicida real-time quantitative PCR (qPCR). Cleaner fish isolates of A. salmonicida and V. splendidus were characterised by virulence gene (vapA) typing, and Multilocus Sequence Analysis (MLSA) in addition to serotyping, respectively. In both cases, isolates of distinct spatiotemporal- and biological origin were also included for comparison