Family: Rhabdoviridae

Genus: Platrhavirus

Distinguishing features

Viruses assigned to the genus Platrhavirus form a distinct monophyletic group based on well-supported Maximum Likelihood or Maximum Clade Credibility trees inferred from complete L sequences. Members of the genus have been detected in flatworms (phylum Platyhelminthes).

Virion

Morphology

Viruses assigned to the genus have not yet been isolated or visualized by electron microscopy.

Nucleic acid

Platrhavirus genomes consist of a single molecule of negative-sense, single-stranded RNA and range from approximately 12.2–15.6 kb (Bodewes et al., 2014, Dheilly et al., 2022).

Proteins

Platrhavirus N, P, M, G and L proteins appear to be homologous with corresponding proteins of other rhabdoviruses. Plartrhavirus G proteins are class I transmembrane glycoproteins. Alignment of platrhavirus G proteins with that of vesicular stomatitis Indiana virus (species Vesiculovirus indiana) indicates likely conservation of 10-12 of the 12 conserved cysteine residues that are typical of animal rhabdovirus G proteins (Walker and Kongsuwan 1999, Roche et al., 2006), and 6 additional conserved cysteine residues that are likely to form 3 more disulphide bridges in the folded protein. Platrhaviruses encode one or more additional proteins, one of which may have the structural characteristucs of a class I viroporin.

Genome organisation and replication

Platrhavirus genomes include the five genes (N, P, M, G and L) encoding the structural proteins and at least one additional gene between the G and L genes (Figure 1.Platrhavirus). Alternative long ORFs may occur in P, M, or one of the additional genes between G and L, but it is not known if they are expressed in infected cells (Figure 1 Platrhavirus).

Figure 1 Platrhavirus. Schematic representation of platrhavirus genomes in reverse (positive-sense) polarity. The five long open reading frames (ORFs) in the N, P, M, G and L genes are shown (open arrows). Additional and alternative ORFs are shown in grey with those encoding predicted class I viroporins shown in yellow.

Biology

Platrhaviruses have been detected by metagenomic sequencing of platyhelminths that parasitise invertebrate and vertebrate hosts (Dheilly et al., 2022). These include the cestode worm Triaenophorus nodulosus and trematode worms (Microphallus sp.2 LB-2020, Sphaeridiotrema pseudoglobulus, Schistosoma turkestanicum and Metorchis orientalis). Fox fecal rhabdovirus (species Platrhavirus vulpes) was detected by metagenomic sequencing of feces from a fox (Vulpes vulpes) collected in Spain (Bodewes et al., 2014). No isolates are currently available for any of these viruses. Available evidence suggests that those platrhaviruses detected in vertebrates are likely due to platyhelminth infestation.

Species demarcation criteria

Viruses assigned to different species within the genus have several of the following characteristics: A) minimum amino acid sequence divergence of 10% in N proteins; B) minimum amino acid sequence divergence of 10% in the L proteins; C) minimum amino acid sequence divergence of 15% in G proteins; D) significant differences in genome organisation as evidenced by numbers and locations of ORFs; E) can be distinguished in virus neutralisation tests; and F) occupy different ecological niches as evidenced by differences in arthropod and/ or vertebrate hosts.

Related, unclassified viruses

Virus names and virus abbreviations are not official ICTV designations.