Red sea bream iridovirus disease (RSIVD) outbreak in Asian seabass (Lates calcarifer) cultured in open estuarine cages along the west coast of India: First report

In the present study, moribund Asian seabass (Lates calcarifer) fish samples were collected from open estuarine cages and observed for clinical signs followed by molecular diagnosis using primers targeting DNA polymerase gene of RSIV reported from OIE. The 568 bp amplicon confirmed the 100% sequence similarity with the reported sequences of RSIV from other countries. It formed the four clusters (RSIV, ISKNV, TBIV, and SDDV) with showing the close relation to Korean RSIV isolate than the RSIV isolate of Japanin the phylogenetic tree and multiple alignment analysis. The histopathogical examinations revealed, necrosed cellular material, melanomacrophage centers, RBC proliferation, lymphocytic infiltration, increased vacuoles and irregular intracytoplasmic viral inclusion bodies were observed in infected fish gill and spleen tissues. The challenge test with tissue homogenate reproduced 100% mortality in the healthy seabass by 6th day post infection (dpi). The first report of the virus in cultured Asian seabass from the region has been notified to OIE.