Experimental Infection of Goldfish (Carassius auratus L.) and Tilapia (Oreochromis niloticus L.) with Koi Ranavirus (KIRV)

Abstract

Background: Ranaviruses are now emerging as serious pathogens for the amphibians, reptiles and fishes. The aim of this study was the determination of the susceptibility of goldfish (Carassius auratus L.) and tilapia (Oreochromis niloticus L.) to experimental infection with Koi ranavirus (KIRV). Methods: The experimental fishes were challenged with an infective dose of KIRV (106.8 TCID50/ml) by intraperitoneal injection (IP), while the control groups were injected with L-15 medium. Target tissues were collected from the experimental fishes infected with virus at 3, 7, 14, 21 and 28 dpi. Tissue samples were subjected to detection of KIRV by polymerase chain reaction (PCR), cell culture assay and histopathological technique. Result: This study reports no specific clinical signs and mortality due to virus infection during the experimental period. Experimentally infected goldfish and tilapia were tested positive for KIRV by PCR at 3 dpi, while target viral DNA was also detected in tilapia at 7 dpi by PCR. However, specific DNA of KIRV was not detected in tissues of experimental fish sampled at later experimental study periods. Cell culture assay revealed no cytopathic effect in the Epithelioma Papulosum Cyprini (EPC) cell line at all sampling time points. Histopathological study revealed focal necrosis, shrunken glomerulus and detached epithelium of tubules in kidney tissue at 3 and 7 dpi in gold fish and melanomacrophage cells and focal necrosis of glomerulus and detachment of the epithelium of tubules in kidney tissue at 3 and 7 dpi in tilapia. Melanomacrophage centers and necrosis were observed in spleen tissues of goldfish and tilapia at 3 and 7 dpi. The challenge study indicated that goldfish and tilapia are not the targeted species for KIRV.