Isolation and characterization of a Cyprinid herpesvirus strain YZ01 from apparently healthy goldfish after rising water temperature

A Cyprinid herpesvirus 2 (CyHV-2) strain YZ01 was isolated from an apparently healthy goldfish with history of exposure to CyHV-2 when the water temperature was heated from 3-6□ to 25□. Brain, kidney, spleen (referred to as BKS) and intestine of sick and dead fish as well as crucian carp (CrCB) or goldfish brain cell (GFB) suspensions inoculated with above tissue homogenate were collected for PCR assay.Infected cell layers were prepared into ultrathin sections for transmission electron microscopy. Virus DNA were purified from cell suspensions for whole genome sequencing and analysis. Intestine and mixed brain, kidney and spleen fluid (BKS) of dead goldfish and BKS-infected CrCB suspensions as well as their subsequent passages were tested positive by PCR. Nucleus deformation, lattice-like arrangement of inclusion bodies and various forms of immature and mature virions in the nucleus, cytoplasm and outside of cell membranes were observed. Whole genome analysis of 7 CyHV-2 strains available in GeneBank showed that all strains’ genomes share very high homology while YZ01 was more close to CyHV-2 CNDF-TB2015 and SY-C1 which are classified as C genotype.