Natural Infection of Two Gourami Species (Trichopodus spp.) With Infectious Spleen and Kidney Necrosis Virus (ISKNV): Clinical, Molecular and Histopathological Findings

Abstract

Infectious spleen and kidney necrosis virus (ISKNV) has a broad host range and poses a significant threat to aquaculture species. Herein, we report two disease outbreaks in snakeskin gourami (Trichopodus pectoralis) in Thailand, marked by skin haemorrhage, scale loss, internal organ discoloration and degeneration and a mortality exceeding 60%. Additionally, three spot gourami (Trichopodus trichopterus) cultured in the same ponds along with snakeskin gourami were found to be affected and tested positive for the virus. Histopathological examination revealed extensive necrosis of haematopoietic tissues in the kidneys and spleen, accompanied by the presence of numerous megalocytic cells in both fish species. Real-time PCR assays, using protocols targeting the major capsid protein (MCP) gene in a broad range of Megalocytivirus genotypes, confirmed the presence of ISKNV in the infected fish. Furthermore, molecular and phylogenetic analyses based on the MCP gene (1362 bp) and the adenosine triphosphatase (ATPase) gene (720 bp) revealed that the ISKNV strains in gourami and other fish hosts were closely related, suggesting possible cross-species transmission. This report extends the host range of ISKNV and highlights the need to prevent the spread of this virus across species boundaries. Further research is needed to understand the pathogenicity and transmission routes of the virus, gain insights into its epidemiology and develop strategies to mitigate disease outbreaks.