Vibrio carchariae causes mass mortalities in Japanese abalone, Sulculus diversicolor supratexta

A new epizootic causing mass mortalities among cultured Japanese abalone, Sulculus diversicolor supratexta, occurred in Kanagawa Prefecture, Japan, during the period from June to October in 1997. Diseased abalone lost the ability to adhere and eventually died on the bottom of aquaria. White spots on the foot were a characteristic sign of the disease. In sections of tissues with lesions, there was necrotic degeneration in muscle fibers, and homogeneous bacterial cells were isolated from the infected tissue. Isolates of this bacterium were Gramnegative, facultatively anaerobic, rod shaped organisms that were motile by a single polar flagellum. They were identified as Vibrio carchariae on the basis of phenotypic characteristics, 16S rRNA gene sequences and DNA-DNA hybridization, although some phenotypic properties of the isolates differed from those of references. Infection experiments confirmed the pathogenicity of the bacterium to Japanese abalone. This is the first report of the isolation of V. carchariae from a diseased shellfish.