Mass mortality in juvenile greasy grouper, Epinephelus tauvina, associated with vacuolating encephalopathy and retinopathy.
Chua, F.H.C., Loo, J.J. and Wee, J.Y.
In: Diseases in Asian Aquaculture II. (Eds. Shariff, M., Arthur, J.R. and Subasinghe, R.P.), Fish Health Section, Asian Fisheries Society, Manila, Philippines.
In 1991, high mortality of 70% was observed among a batch of greasy grouper (Epinephelus tauvina) fry in a commercial net-cage fish farm in Singapore. Affected fry displayed a loss of equilibrium, uncoordinated and weak swimming movements, swimming in circles and, in some cases, spastic lateral flexure of the body. The disease lasted about 2wk, with heaviest mortalities occurring from 7 to 9d after the onset of clinical signs. There were no visible external or internal gross lesions. Parasites and bacteria were not consistently recovered and were considered to be opportunistic invaders. Histological examinations revealed vacuolating encephalopathy and retinopathy in affected fry. A cytopathic agent was isolated in a barramundo perch (Lates calcarifer) cell line inoculated with suspensions of heads and viscera from affected fish. These findings suggested a neurotropic viral disease.