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Piscihepeviruses have only been isolated from salmonid fish in North America. Genome organisation is similar to that of orthohepeviruses but piscihepeviruses are phylogenetically distinct (Smith et al., 2015, Batts et al., 2011).
Virions have a diameter of 31 nm (Batts et al., 2011). Other properties of the virion have not been described.
The 5′ untranslated region of cutthroat trout virus is longer (100 nt) than has been observed for orthohepevirues (< 35nt). Three open reading frames are present, arranged as for other members of the Hepeviridae (Figure 4.Hepeviridae) except that ORF3 of cutthroat trout virus overlaps the central region of ORF2 rather than the 5′ terminus as is typical of orthohepeviruses. The protein encoded by ORF3 has a predicted isoelectric point of 11.8, similar to that encoded by hepatitis E virus (12.5), although this reading frame is not conserved in another partial genome sequence that covers this region (AF030878, haemorrhagic kidney syndrome virus). The capsid protein encoded by ORF2 has a predicted isoelectric point of 5.7 with acidic residues clustered at the COOH-terminus; this contrasts to the basic capsid protein encoded by ORF2 of orthohepeviruses (Batts et al., 2011).
Cutthroat trout virus has been detected in the ovarian fluids of several trout species and is widely distributed in the western United States (Hedrick et al., 1991). A similar virus has been detected in salmon in New Brunswick, Canada (Kibenge et al., 2000). Although not associated with disease, cutthroat trout virus produces a slow, focal type of cytopathic effect in the Chinook salmon embryo cell line CHSE-214 without destroying the monolayer. Virus can sometimes be re-isolated from infected animals after 4-6 weeks. A single complete genome sequence is available for cutthroat trout virus as well as one partial genome sequence (haemorrhagic kidney syndrome virus) and >30 partial helicase sequences; all of these virus sequences are closely related to that of cutthroat trout virus with nucleotide p-distances of < 0.08 and amino acid distances of < 0.06.
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