Abstract
Mass mortalities of hatchery‐reared juvenile groupers have occurred in southern Taiwan. The diseased fish swam in a darting, corkscrew fashion. Light microscopy revealed vacuolation in the brain tissue. Electron microscopy showed numerous non‐enveloped, cytoplasmic viral particles (20–25 nm in diameter) in the brain cells, and many virions were enclosed in the membrane‐bound organelles of the cells. Two structural proteins 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 segments of striped jack nervous necrosis virus (SJNNV) RNA2 genes suggest that this virus is a fish nodavirus, and is designated as GNNV 9410 strain (grouper nervous necrosis virus strain 9410). This is the first case report of viral nervous necrosis among marine fish in Taiwan.