Identification and characterization of a new strain of Ictalurid herpesvirus 1 isolated from channel catfish in China

Ictalurid herpesvirus poses a significant threat to global catfish aquaculture. In this study, an Ictalurid herpesvirus 1 (IcHV1) strain, isolated from diseased channel catfish in China, was investigated. Initially, PCR assays using IcHV1 gene primers detected viral gene fragments in the tissues of diseased catfish. Meanwhile, transmission electron microscopy (TEM) confirmed the presence of herpesvirus-like virions. This virus, designated IcHV1-JS01, was isolated through incubation with CCO/BB cells, which was verified via PCR and immunoblotting; and infections with this virus triggered cytopathic effects and syncytia formation in CCO/BB cells. Subsequently, a catfish-challenge experiment proved its high virulence, with extremely high viral loads in dead fish. High-throughput sequencing of IcHV1-JS01 revealed a 133,530-bp genome, which shared high similarity with known viral genome, but harboured numerous variations. Phylogenetic analysis classified IcHV1-JS01 as a member of the genus Ictavirus, representing a unique Chinese isolate. Collectively, these findings will facilitate the development of epidemiological investigations and disease control strategies, protecting the catfish farming industry.