Betanodavirus-associated mortality in Asian seabass (Lates calcarifer, Bloch) cultured in indoor tanks and sea cages

Sea cage farming of Asian seabass is a prospective aquaculture activity in India. Reports from India on betanodavirus-induced mortality in marine fish culture are not many. An outbreak of viral encephalopathy and retinopathy associated with red-spotted grouper nervous necrosis virus (RGNNV) genotype of betanodavirus in Asian seabass juveniles reared in indoor tanks and sea cages is described in the present paper. Mortality was less severe in cages when compared to tanks. Sequence analysis of the coat protein gene indicated that the virus belonged to RGNNV genotype but found to be distinct from other reported RGNNV isolates. Virus was able to induce cytopathic effects in fish cell lines. Light microscopic features of the disease are also described.