Vol. 9, Special Issue 2, Part F (2025)

This study investigates the lethal dose (LD₅₀) and pathological changes associated with Infectious Spleen and Kidney Necrosis Virus (ISKNV) infection in monosex genetically improved and farmed tilapia (GIFT) (Oreochromis niloticus). The virus was propagated in the Sahul Indian Seabass Spleen (SISS) cell line, displaying notable cytopathic effects. The LD₅₀ assay determined the lethal dose of ISKNV for GIFT tilapia to be 1.7×10⁵ copies/µl with mortality rates ranging from 15% to 85% across different viral dilutions. Infected fish exhibited clinical signs such as splenomegaly, significant haemorrhaging, and behavioural changes like erratic swimming and anorexia. The infection was confirmed by Polymerase chain reaction (PCR) assays using major capsid protein (MCP) gene The successful experimental infection of ISKNV in GIFT tilapia, demonstrates high mortality rates and significant pathological changes. Histopathological analysis further substantiates these findings by revealing characteristic features of ISKNV infection, such as degenerated epithelium, melano macrophage centres (MMC), increased interstitial spaces, and ruptured glomeruli and renal tubules. This study provides valuable insights into the severity and progression of ISKNV infection in GIFT tilapia, offering a foundation for developing effective disease control strategies in aquaculture.