Reoviruses of Aquatic Organisms

The family Reoviridae includes viruses with a multisegmented, double-stranded RNA genome enclosed in one to three capsid shells and lacking an envelope. Member viruses occur in a wide range of animals (mammals, birds, reptiles, fish and crustaceans), insects, plants and fungi. While the original members of this family, genus Orthoreovirus, were considered nonpathogenic, the ability to cause disease is variable in the different genera of this family. Reoviruses of fish form two distinct groups (or genera): the genus Aquareovirus with 11 segments, and the genus Orthoreovirus with 10 segments and containing the newly discovered piscine orthoreovirus. Reoviruses of crustaceans make up the genus Cardoreovirus and a new proposed genus Crabreovirus with 12 segments, but several isolates remain unassigned. This chapter describes the comparative virology of members in the family Reoviridae in general, helping to understand the aquatic reoviruses and their capacity to cause disease.