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

A new epizootic causing mass mortalities among cultured Japanese abalone, S ulculus diversicolor supratexta, occurred in Kanagawa Prefecture, Japan, du ring the period from June to October in 1997. Diseased abalone lost the abi lity 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 homoge neous bacterial cells were isolated from the infected tissue. Isolates of t his bacterium were Gramnegative, facultatively anaerobic, rod shaped organi sms that were motile by a single polar flagellum. They were identified as V ibrio 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 conf irmed the pathogenicity of the bacterium to Japanese abalone. This is the f irst report of the isolation of V. carchariae from a diseased shellfish.