MASS MORTALITIES ASSOCIATED WITH VIRAL NERVOUS NECROSIS (VNN) DISEASEIN 2 SPECIES OF HATCHERY-REARED GROUPER, EPINEPHELUS-FUSCOGUTATUS ANDEPINEPHELUS-AKAARA (TEMMINCK AND SCHLEGEL)

Mass mortalities of hatchery-reared juvenile groupers have occurred in southern Taiwan. The diseased fish swam in a darting, corkscrew fashi on. Light microscopy revealed vacuolation in the brain tissue. Electro n microscopy showed numerous nonenveloped, cytoplasmic viral particles (20-25 nm in diameter) in the brain cells, and many virions were encl osed in the membrane-bound organelles of the cells. Two structural pro teins of the purified grouper virus, with molecular weights of 44 and 43 kDa, were revealed by SDS-PAGE. Moreover, the results of RT-PCR and nested PCR diagnosis using primers specific to the T2 and T4 target s egments of striped jack nervous necrosis virus (SJNNV) RNA2 genes sugg est that this virus is a fish nodavirus, and is designated as GNNV 941 0 strain (grouper nervous necrosis virus strain 9410). This is the fir st case report of viral nervous necrosis among marine fish in Taiwan.