Lyssavirus (from the Greek lyssa "rage, fury, rabies" and the Latin vīrus) is a genus of RNA viruses in the family Rhabdoviridae, order Mononegavirales. Mammals, including humans, can serve as natural hosts. The genus Lyssavirus includes the causative agent (rabies virus) of rabies.

Phylogeny

Other unclassified viruses are:

  • Lyssavirus formosa, Taiwan bat lyssavirus
  • Lyssavirus kotalahti, Kotalahti bat lyssavirus
  • Lyssavirus phala, Phala bat lyssavirus

Virology

Structure

Lyssavirions are enveloped, with bullet shaped geometries. These virions are about 75 nm wide and 180 nm long. The lyssavirus genus can be divided into four phylogroups based upon DNA sequence homology. Phylogroup I includes viruses, such as Rabies virus, Duvenhage virus, European bat lyssavirus types 1 and 2, Australian bat lyssavirus, Khujand virus, Bokeloh bat lyssavirus, Irkut virus, and Aravan virus. Phylogroup II contains Lagos bat virus, Mokola virus, and Shimoni bat virus. West Caucasian bat lyssavirus is the only virus that is a part of phylogroup III. Ikoma lyssavirus and Lleida bat lyssavirus are examples in phylogroup IV. West Caucasian bat lyssavirus was classified within its own phylogroup because it is the most divergent lyssavirus that has been discovered.

{| class="wikitable sortable" style="text-align:center"

|-

! Genus !! Structure || Symmetry !! Capsid !! Genomic arrangement !! Genomic segmentation

|-

|Lyssavirus||Bullet-shaped||||Enveloped||Linear||Monopartite

|}

Evolution

Phylogenetic studies suggest that the original hosts of these viruses were bats. However, the recent discovery of lyssavirus sequences from amphibians and reptiles challenges the mammalian origin of lyssaviruses. The greater antigenic diversity of lyssaviruses from Africa has led to the assumption that Africa was the origin of these viruses. An examination of 153 viruses collected between 1956 and 2015 from various geographic locations has instead suggested a Palearctic origin (85% likelihood) for these viruses. Date estimates (95% likelihood) for the most recent common ancestor were very broad – between 3,995 and 166,820 years before present – which suggests there is further work to be done in this area. Although bats evolved in the Palearctic, their origins antedate that of the lyssaviruses by millions of years, which argues against their co-speciation. The evolution rate in the N gene in the Africa&nbsp;2 lineage has been estimated to be 3.75×10<sup>−3</sup> substitutions per site per year. This rate is similar to that of other RNA viruses.

Life cycle

Viral replication is cytoplasmic. Entry into the host cell is achieved by attachment of the viral G glycoproteins to host receptors, which mediates clathrin-mediated endocytosis. Replication follows the negative stranded RNA virus replication model. Negative stranded RNA virus transcription, using polymerase stuttering, is the method of transcription. The virus exits the host cell by budding and by tubule-guided viral movement.

Wild mammals, especially bats and certain carnivores, serve as natural hosts. Transmission routes are typically via bite wounds.

Epidemiology

Classic rabies virus is prevalent throughout most of the world and can be carried by any warm blooded mammal. The other lyssaviruses have much less diversity in carriers. Only select hosts can carry each of these viral species. Also, these other species are particular only to a specific geographic area. Bats are known to be an animal vector for all identified lyssaviruses except the Mokola virus.

See also

  • Bat-borne virus

References

Further reading

  • Rhabdoviridae
  • Lyssavirus
  • Viralzone: Lyssavirus
  • ICTV