Characterization of an iridovirus detected from cultured turbot Scophthalmus maximus in Korea

Juvenile turbot Scophthalmus maximus that became sick during an outbreak of disease at mariculture facilities at Go-Chang, Korea, in 2003, were examined to identify the cause of the disease. The fish had pale body color, an enlarged abdomen, protruding eyes, an enlarged spleen and kidney, and pale gills and/or liver. Histopathogical examination revealed basophilic enlarged cells in the kidney, spleen, gills, heart, stomach, intestine, liver, pancreas and skin. Hexagonal viral particles with a diameter of 136 to 159 nm were observed in the enlarged cells. A specific 1299 bp fragment of the major capsid protein (MCP) gene of the turbot iridovirus (TBIV) was amplified by PCR. Sequence homology was greater than 93.76% between the MCP gene in TBIV and the same gene in 5 viruses in the tentatively proposed genus Tropivirus (family Iridoviridae): red sea bream iridovirus, sea bass iridovirus, grouper sleepy disease iridovirus, African lampeye iridovirus and dwarf gourami iridovirus. These results suggest that the virus detected from turbot is similar to the proposed genus Tropivirus.