Isolation and characterisation of a novel rhabdovirus from snakehead fish showing surface ulcerations and mortality from India: First report

Abstract

A novel viral agent was isolated from striped snakehead (Channa striata Bloch, 1793) suffering from mortality with dermal ulcerations and haemorrhagic areas in South India. The virus growth was well supported in striped snakehead (SSN-1) and sea bass caudal peduncle (SBCP2a) cell lines at 27 °C while EPC cells were refractory to the virus. Transmission electron microscopy of the infected cells revealed bullet shaped virions with the size ranging from 150 to190 nm length and 46 to 60 nm width. RT-PCR targeting block III fragment of the rhabdovirus L polymerase gene amplified an expected genomic portion of 483 bp. Phylogenetic analysis indicated 91% homology to the equivalent region of the reported snakehead rhabdovirus L polymerase. Experimental infection studies using cell culture grown virus induced 100% morality in juvenile snakehead in five days. Fish showed listlessness, neural pathology and lethargy before dying. Clinical signs included haemorrhages at the fin bases, exophthalmia, darkening of the skin, vascular congestion around the eyes and reddish iris and surface ulcers. The virus caused extensive necrosis of kidney, spleen and liver. The clinical pathology along with the morphology and phylogenetic homogeneity indicates that the virus belongs to the genus Novirhabdovirus under the family Rhabdoviridae. The present study forms the first report of isolation of a fish rhabdovirus in India.