Ranavirus belonging to the family Iridoviridae is one of the most important emerging pathogens that affect farmed and wild fishes of both economic and ecological importance in aquaculture worldwide. Recently we isolated a ranavirus from infected koi (koi ranavirus, KIRV) which was closely related to Santee Cooper group of viruses of the genus Ranavirus. The aim of this study was to determine the pathogenicity of koi ranavirus (KIRV) in rohu, Labeo rohita (Hamilton), one of the widely cultured freshwater fish in India.
In the present study, rohu fingerlings were experimentally infected with KIRV by intraperitoneal injection with 50 µl of the virus preparation having an infectious dose of 106.8 TCID50/ml. After injection, tissues such as spleen and kidney of rohu challenged with the virus were collected at 3, 7, 14, 21 and 28 dpi for investigation of the presence of KIRV by polymerase chain reaction (PCR) and cell culture assay. Tissues were also subjected to histopathological analysis. KIRV was detected in pooled samples of kidney and spleen from challenged fishes after 3 dpi by PCR, while no positive results were obtained from all other time points. Pooled tissues of kidney and spleen were processed for virological examination using EPC (epithelioma papulosum cyprini) cell line. However, no cytopathic effect was observed in the cell line at all time points. The results of the histopathological analysis showed necrosis of renal tubules and enlarged glomeruli in kidney tissue at 3 and 10 dpi and melanomacrophage cells were observed in both kidney and spleen tissue at 3 dpi.
On the whole, results reveal that there is no clear clinical pathology observed in rohu fingerlings following experimental infection with KIRV.