-positive, a novel teleost pathogen isolated from cultured barramundi.

Abstract

Members of the genusare emergent pathogens of cultured eels, as well as several characid and cyprinid species. Since 2013,has been reported from diseased barramundi () cultured in North America; we recovered 8isolates from diseased fish during different outbreaks from the same farm. Theisolates from barramundi were compared phenotypically and genetically toisolates characterized from ornamental fish andrecovered from aquatic and terrestrial animals. All barramundi isolates were PCR-positive for the surface protective antigen type B () gene, and shared &#x2265;&#x2009;99.7% sequence similarity among concatenated multilocus sequence analysis gene sequences, indicating a high degree of genetic homogeneity. These isolates were >&#x2009;99% similar to otherpositive isolates from marine invertebrates and marine mammals, consistent with findings for othertypes. Theandisolates shared <&#x2009;98% similarity, as well as <&#x2009;90% similarity withpositive. Similar clonality among theisolates was observed using repetitive element palindromic PCR. In experimental intracoelomic injection challenges conducted to fulfill Koch postulates, 67% of exposed tiger barbs () died within 14 d of challenge. Our study supports previous work citing the genetic variability ofspp.types and the emergence of members of the genusas nascent fish pathogens.