First Report of Infectious Spleen and Kidney Necrosis Virus (ISKNV) Infection in Dwarf Gourami (Trichogaster lalius) from India

Infectious Spleen and Kidney Necrosis Virus (ISKNV), a member of the genus Megalocytivirus within the family Iridoviridae, has emerged as a significant pathogen in both ornamental and food fish species globally affecting the aquaculture industry. This study reports the molecular detection and phylogenetic characterization of ISKNV in two ornamental fish species namely dwarf gourami (Trichogaster lalius) and angelfish (Pterophyllum scalare). Out of 38 samples screened, two were found positive for major capsid protein (MCP) gene with a 563 bp product by using OIE-recommended primers. The sequence analysis using BLAST, revealed 98.40% and 98.76% nucleotide identity with reference ISKNV strains for dwarf gourami and angelfish, respectively. Phylogenetic analysis of MCP gene sequences, clustered the isolates from this study within the ISKNV clade. Clinically, the infected angelfish exhibited whirling behavior and internal signs such as hepatic hemorrhage and splenomegaly, while the dwarf gourami remained asymptomatic. These findings underscore the potential for subclinical ISKNV infections and highlight the risk of viral dissemination through transboundary ornamental fish trade and cohabitation practices in local shops. This study represents the first confirmed report of ISKNV infection in dwarf gourami from India and emphasizes the need for enhanced molecular surveillance and biosecurity measures in ornamental aquaculture systems.