Incidence of Vibrio during dermal and systemic infections of the spotted sand bass (Paralabrax maculatofasciatus Steindachner: 1868) in captivity

Abstract

The incidence of Vibrio in dermal and internal injuries was evaluated in captive broodstock of spotted sand bass, Paralablax maculatofasciatus. During haemorragic infections the associated bacteria were isolated on thiosulfate-citrate-bile-sucrose agar (TCBS) and on Marine Agar 2216. Isolates were presumptively identified and the pathogenicity was experimentally evaluated. Vibrio alginolyticus, V. cholerae, V. fluvialis, V. parahaemolyticus, V. vulnificus and Vibrio sp. were present in external injuries. Vibrio alginolyticus was consistently predominant in dermal injuries. Clinical signs recorded during the vibriosis outbreaks included hemorrhages and petechiae on body surfaces, which were most severe at the base of the pelvic fins and in the opercular region. Hemorrhages and necrosis were observed on the fins. Affected fish became inactive and anorexic. Internally, hemorrhages in the intestine and a pale liver were observed. During experimentally induced infections, the fish inoculated with 10⁸ cells of the strain VPb-C7 (identified as V. alginolyticus) developed clinical signs and mortality was recorded.