An outbreak of Vibrio alginolyticus infection in aquarium-maintained dark-spotted (Himantura uarnak) and Tahitian (H. fai) stingrays

Vibrio alginolyticus was isolated from captive-bred adult dark-spotted stingrays (Himantura uarnak) and Tahitian stingrays (Himantura fai) housed at the Hurghada Grand Aquarium (Egypt). The pathogen was isolated from skin ulcers, as well as from the internal organs of diseased and freshly died rays. Most of rays showed dorsal disc surface skin lesions characterized by the presence of whitish necrotic tissue. The total mortality was 25% during the outbreak, the histopathological pictures were also recorded. Phenotypic and biochemical characters as well as species-specific PCR confirmed the pathogen as V. alginolyticus MK170250. The isolated bacteria were sensitive to ampicillin, amikacin, streptomycin, neomycin, oxytetracycline, tetracycline, chloramphenicol, erythromycin, norfloxacin, and ciprofloxacin, but resistant to cephalothin. Antibiotic therapy was conducted with intramuscularly injection of amikacin at 3-5 mg/kg of fish on alternate days for five doses and resulted in preventing the clinical signs and mortality. This article represents the first report of V. alginolyticus infection in dark-spotted and Tahitian stingrays, and highlights the potential pathogenic role of this microorganism in elasmobranchs kept in an aquarium. (C) 2019 National Institute of Oceanography and Fisheries. Hosting by Elsevier B.V.