Hepeviruses of aquatic organisms

Originally reported in California, the cutthroat trout virus (CTV) has now been isolated from nine species of salmonids in North America. Early work focused on the replication and physical characteristics of the virus, but 20 years later was determined to be most closely related to the hepatitis E virus. The small genome is positive-sense, single-stranded RNA similar to other members of the family Hepeviridae, which now contains its own genus Piscihepevirus with two distinct genotypes, CTV-1 and CTV-2. While CTV has not been associated with acute disease in fish, the virus could form persistently infected cell cultures that may aid research in treating hepatitis E-like viruses affecting humans or other animals. Interestingly, trout exposed to CTV were protected for about a month against subsequent exposure to the infectious hematopoietic necrosis virus. Replicating agents suspected to be CTV can be confirmed by polymerase chain reaction (PCR), quantitative PCR, and sequencing. Other unclassified hepeviruses detected in fish using viral metagenomics include Wenling fish hepevirus, Wenling moray eel hepevirus, Murray–Darling carp hepevirus, and eastern mosquitofish hepevirus. The family Hepeviridae has been placed in the order Hepevirales together with the family Matonaviridae (rubella virus), with member viruses having amino acid homology in the helicase and replicase regions of the nonstructural proteins. In addition, using next-generation sequencing, a hepe-like sequence was characterized in diseased giant freshwater prawn Macrobrachium rosenbergii and named Crustacea hepe-like virus 1. Thus the family Hepeviridae continues to expand among aquatic animal hosts.