Group Group V ((−)ssRNA) Family Bunyaviridae | Order Unassigned Rank Genus | |
 | ||
Similar Bunyaviridae, Phlebovirus, Orthobunyavirus, Hyalomma, Tospovirus | ||
Medical vocabulary what does nairovirus mean
Nairovirus is a genus in the family Bunyaviridae that include viruses with circular, negative-sense single stranded RNA. It got its name from the Nairobi sheep disease that affects the gastrointestinal tracts of sheep and goats. The vast majority, and perhaps all viruses in this genus are tick-borne viruses that can have human or other vertebrate hosts.
Contents
Medical vocabulary what does nairovirus mean
Taxonomy
The Nairobi sheep disease virus (NSD) is the prototype virus of the genus.
NSD is found in East and Central Africa, and causes acute hemorrhagic gastroenteritis in sheep and goats.
Serogroups
The genus is divided into at least nine serogroups. The Hughes and Sakhalin serogroups appear to be sister groups.
Serogroups
Crimean-Congo hemorrhagic fever
Dera Ghazi Khan
Hughes
Kasokero
Nairobi sheep disease
Qalyub
Sakhalin
Tamdy
Thiafora
Within each serogroup are a number of related viruses:
Crimean-Congo hemorrhagic fever serogroup:
Crimean-Congo hemorrhagic fever virus Hazara virus Tofla virusDera Ghazi Khan serogroup:
Abu Hammad virus Abu Mina virusHughes serogroup:
Farallon virus Hughes virus Puffin Island virus Punte Salinas virus Raza virus Soldado virus Zirqa virusKasokero serogroup:
Kasokero virus Yogue virusNairobi sheep disease serogroup:
Dugbe virus Ganjam virus Kupe virus Nairobi sheep disease virusQalyub serogroup:
Bandia virus Chim virus Geran virus Qalyub virusSakhalin serogroup:
Avalon virus Paramushir virus Sakhalin virus Tillamook virusTamdy serogroup:
Burana virus Tamdy virusThiafora serogroup:
Erve virus Thiafora virusGenome
Nairovirus genomes are negative sense, single-stranded RNA. The complete genome is about 17,100–22,800 nucleotides long, and is divided into three segments: large, medium, and small. The large segment is about 11000–14400 nucleotides long (11–14.4 kb), and it encodes the viral polymerase. The medium segment is about 4,400–6,300 nucleotides long (4.4–6.3 kb), and it encodes for glycoproteins G¬n and Gc. The small segment is about 1,700–2,100 nucleotides long (1.7–2.1 kb), and it encodes the nucleocapsid protein.
The genome has terminally redundant sequences, with the sequences being repeated at both ends. The terminal nucleotides are base-paired forming, non-covalently closed, circular RNA. Both the 5’ and 3’ ends have conserved regions, 9 nucleotides in length. The sequences are, 5’end: UCUCAAAGA, and 3’end: AGAGUUUCU.
Virion
The virions for viruses in this genus have a spherical shape. They range in size from about 80–120 nm in diameter, with 50% of their weight attributed to proteins and 20–30% of their weight attributed to lipids. The ribonucleocapsid is filamentous, having a length of about 200-300 nm and a width of about 2–2.5 nm.
These nucleocapsids are surrounded by a single envelope that has projections made of glycoproteins protruding from its surface. These projections evenly cover the surface of the virion, and are about 5–10 nm long. They aid in attachment to the host receptor in replication.
Replication
Nairoviruses attach to the host receptor by their Gn-Gc glycoprotein dimer. The virus is then endocytosed into the host cell via a vesicle. The ribonucleocapsid segments are released into the cytoplasm, commencing transcription. Transcription and replication occur within the cell, and the newly synthesized virions are released by budding.
Transmission & Distribution
Members of this viral genus infect many different vertebrate hosts, and are transmitted via ticks.
Members of the genus Nairovirus may be found the world over, wherever their arthropod vectors and vertebrate hosts are found together.
Evolution
Phylogenetic analysis has shown that these viruses fall into two major monophyletic groups, the hard (Ixodidae) and soft (Argasidae) tick-vectored groups. Fossil and phylogenetic data places the hard tick-soft tick divergence between 120 million years ago and 92 million years ago. This suggests that the Nairoviruses have been associated with these ticks for over 100 million years.
Additionally, nairoviruses vectored by ticks of the genera Argas, Carios and Ornithodoros form three separate monophyletic lineages, again supporting the suggestion of host-virus cospeciation.
The hard bodied tick serogroups are
The soft bodied tick serogroups are
The tick vectors for the Kasokero and Thiafora serogroups are not currently known.
Clinical importance
Only four viruses in this genus have, to date, been recognised as human pathogens:
A fifth— Erve virus —may also be pathogenic for humans.