Mass mortalities associated with viral nervous necrosis in hatchery-rearedgroupers in the People's Republic of China

The viral etiology of mass mortalities of groupers, Epinephelus coioides an d E. akaara, cultured in the People's Republic of China was examined. Disea se outbreaks occurred in 7 to 45 day-old fish with erratic swimming motion and marked vacuolation was observed in the brain and retina of the affected fish. The piscine nodavirus (the Betanodavirus), the causative agent of vi ral nervous necrosis (VNN), was detected in the affected tissues by electro n microscopy, indirect fluorescent antibody test and reverse transcription- polymerase chain reaction. This paper is the first record of the agent in t he People's Republic of China.