The family Nodaviridae includes two genera, Alphanodavirus and Betanodavirus. The family name derives from the Japanese village of Nodamura where Nodamura virus was first isolated from Culex tritaeniorhynchus mosquitoes. Virions are non-enveloped and spherical in shape with icosahedral symmetry (T=3) and diameters ranging from 25 to 33 nm. The genome consists of two molecules of single-stranded positive-sense RNA: RNA1 and RNA2. The virion capsid consists of 180 protein subunits arranged on a T=3 surface lattice. Alphanodaviruses infect insects, whereas betanodaviruses are pathogens of fish. This is a summary of the International Committee on Taxonomy of Viruses (ICTV) Report on the taxonomy of the Nodaviridae, which is available at www.ictv.global/report/nodaviridae.

White tail disease (WTD) was found to be a serious problem in hatcheries and nursery ponds of Macrobrachium rosenbergii in India. The causative organisms have been identified as M. rosenbergii nodavirus (MrNV) and its associated extra small virus (XSV). Experimentally transmitted to healthy animals, they caused 100% mortality in post-larvae but failed to cause mortality in adult prawns. The RT-PCR assay revealed the presence of both viruses in moribund post-larvae and in gill tissue, head muscle, stomach, intestine, heart, hemolymph, pleopods, ovaries and tail muscle, but not in eyestalks or the hepatopancreas of experimentally infected adult prawns. The presence of these viruses in ovarian tissue indicates the possibility of vertical transmission. Pleopods have been found to be a suitable organ for detecting these viruses in brooders using the RT-PCR technique.