Outbreak of iridovirus infection in grouper (Epinephelus sp.) at open sea cages Langkawi, Kedah, Malaysia

An outbreak of Iridovirus was diagnosed in giant grouper (Epinephelus lanceolatus) and tiger grouper (Epinephelus,fuscoguttatus) reared in cages, Langkawi, Kedah in February, 2005. The tiger grouper fry which were originated from Indonesia displayed no visible sign of disease on the day of stocking but after 10 days of culture, the affected fry and some juveniles from few other cages in the farm exhibited signs loss of equilibrium, abdominal distention (dropsy), weak swimming movement on the water surface and death after 24-48 hours of clinical illness. Mortality rate estimated to be about 30% in two weeks. Gross observation and necropsy examination showed signs of viral infections such as darkening of body coloration, dropsy and enlarged spleen in tiger grouper fry (E. fuscoguttatus). Similar clinical signs with skin lesions were also observed in grow out giant grouper (E. lanceolatus). Multiple infections of parasites (Benedenia sp., Trichodina sp.), bacteria (V. alginolyticus) and Iridovirus were diagnosed in most of the samples tested. Iridovirus infection and capsalid Benedenia sp. infestation were serious problems to fish culturist in Langkawi, Kedah, Malaysia