Malacoherpesviridae

Malacoherpesviridae is a family of DNA viruses in the order Herpesvirales. Molluscs serve as natural hosts, making members of this family the only known herpesviruses to infect invertebrates. There are currently only two species recognised in this family, both classified into separate genera. Disease associated with this family includes sporadic episodes of high mortality among larvae and juveniles. The family name Malacoherpesviridae is derived from Greek word 'μαλακός (malacos) meaning 'soft' and from Greek word 'μαλάκιον (malakion) meaning 'mollusc'.

Taxonomy

 * Ostreavirus Davison et al., 2009
 * Ostreid herpesvirus 1 Davison et al., 2009 – acronym: OsHV-1, common name: oyster herpesvirus, its host are bivalves (oysters) and the octopus species Octopus vulgaris.
 * Aurivirus Savin et al., 2010, syn. Haliotivirus
 * Haliotid herpesvirus 1 Savin et al., 2010 – acronym: HaHV-1 or AbHV-1 (Corbeil et al., 2017, J Inv Pathol, 146:31-35), common name: abalone herpesvirus, its hosts are abalone sea snails, i.e. Haliotis spp. such as Haliotis diversicolor.

Acute viral necrosis virus, which affects scallops such as Chlamys farreri, appears to be a variant of Ostreid herpesvirus 1.

Structure
Viruses in Malacoherpesviridae are enveloped, with icosahedral and spherical to pleomorphic geometries, and T=16 symmetry. The diameter is around 150-200 nm. Genomes are linear and non-segmented, around 134kb in length.

Life cycle
Viral replication is nuclear, and is lysogenic. Entry into the host cell is achieved by attachment of the viral glycoproteins to host receptors, which mediates endocytosis. DNA templated transcription is the method of transcription. Molluscs serve as the natural host. Malacoherpesviridae may have the ability to infect across species, a feature not typically observed in vertebrate herpesviruses. This ability appears to be restricted to related mollusc species.