First record of iridovirus (ISKNV) infections in Fourfinger threadfin from Kuwait

Abstract

Following an initiative by the Govt. of Kuwait and the Kuwait Institute for Scientific Research (KISR), the institute started simultaneous efforts of domestication of locally caught fish and hatchery production of Fourfinger threadfin (FFT, Eleutheronema tetradactylum), locally called Sheem. A private farm and KISR are working together to optimize the conditions for growth and spawning performances under the environmental conditions of Kuwait. During these efforts, infectious spleen and kidney necrosis virus (ISKNV), an important fish pathogen from Iridoviridae, caused mortalities of the FFT sub-adults (150–200 g). We noticed that the mortality was associated with anorexia, haemorrhages of the snout, fin bases, and scale pockets. We also noticed that this was typical to one of the tanks that had consistently high ammonia (0.2–0.25 ppm) levels in the water, and all 35 sub-adults died within 4–5 days. Diagnostics (molecular and electron microscopy examinations) revealed ISKN iridovirus as the causative. We noticed viral particles of 150–200 nm in the tissue sections of the skin, gills, heart, liver, spleen, kidney, and intestine. The major capsid protein (MCP) gene sequence analysis confirmed the results, revealing 98 % similarity with the laminin-type epidermal growth factor-like protein gene of ISKNV. The present report is the first record of ISKNV infections in FFT and from Kuwait. The study aimed to decipher the cause of illness and mortality of cultured FFT.