Channel catfish virus gene expression in experimentally infected channel catfish, Ictalurus punctatus (Rafinesque).

Channel catfish virus (CCV) produces an acute haemorrhagic disease in fingerling channel catfish and establishes latent infection in fish that survive the primary infection. This study investigated CCV gene expression in tissues of experimentally infected fish. Reverse transcriptase polymerase chain reaction assays were developed for detection of transcripts expressed by each of the CCV direct repeat region genes in CCV-infected channel catfish ovary cells and in tissues of infected fish. Immediate-early, early and late gene transcripts were detected in the blood, brain, kidney and liver tissues of acutely infected catfish demonstrating active viral replication in multiple tissues during the early stages of CCV infection. However, there was no evidence for viral replication by 24 days post-infection in tissues of fish that survived the acute disease. Viral latency-associated transcripts encoded by CCV direct repeat genes were not detected in latently infected catfish. The results of this study provide a foundation for further studies to investigate the molecular basis of CCV pathogenesis and latency.