Vibrio tapetis from wrasse used for ectoparasite bio-control in salmon farming: phylogenetic analysis and serotyping

Abstract

So-called 'cleaner fish', including various wrasse (Labridae) species, have become increasingly popular in Norwegian salmon farming in recent years for biocontrol of the salmon louse Lepeophtheirus salmonis. Cleaner fish mortalities in salmon farms are, however, often high. Various bacterial agents are frequently associated with episodes of increased cleaner fish mortality, and Vibrio tapetis is regularly cultured from diseased wrasse. In the present study, we investigated the genetic relationships among 54 V. tapetis isolates (34 from wrasse species) by multilocus sequence analysis (MLSA; rpoD, ftsZ, pyrH, rpoA and atpA). In the resulting phylogenetic tree, all wrasse isolates belonged to sub-clusters within V. tapetis subsp. tapetis. Slide agglutination testing further confirmed the complete dominance amongst these isolates of 4 O-antigen serotypes, designated here as V. tapetis subsp. tapetis serotypes O1, O3, O4 and O5, respectively. A pilot challenge trial using serotypes O3, O4 and O5 did not indicate high pathogenicity towards ballan wrasse Labrus bergylta, thus questioning the role of V. tapetis as a primary pathogen of this fish species.

Cleaner fish in aquaculture: review on diseases and vaccination

“…bacteria (Scholz et al, 2018a;Hjeltnes et al, 2019). V. splendidus and V. tapetis have been reported as pathogenic for certain wrasse species (Sigmund et al, 2003;Bergh & Samuelsen, 2007;Johansen et al, 2016a), although recent studies have suggested they might represent opportunistic pathogens rather than causing primary infections (Gulla et al, 2015;Gulla et al, 2017). V. tapetis is also the cause of brown ring disease in the bivalve Ruditapes philippinarum (Paillard et al, 2006).…”

“…splendidus and V . tapetis have been reported as pathogenic for certain wrasse species (Sigmund et al, 2003; Bergh & Samuelsen, 2007; Johansen et al, 2016a), although recent studies have suggested they might represent opportunistic pathogens rather than causing primary infections (Gulla et al, 2015; Gulla et al, 2017). V .…”

MALDI-TOF MS as a promising tool to assess potential virulence of Vibrio tapetis isolates

“…quintayensis (Levican et al, 2017). However, using genotyping methods, such as Randomly Amplified Polymorphic DNA (RAPD) PCR (Romalde et al, 2002) and multilocus sequence analysis (MLSA) (Gulla et al, 2017) different clusters were defined between V. tapetis subspecies. This indicates that the phylogeny of V. tapetis is not yet completely unraveled.…”