View source for Biology:Betanodavirus

{{Short description|Genus of viruses}}
{{Virusbox
| taxon = Betanodavirus
| image = Journal.ppat.1005203.Fig.S2.tif

| image_caption = Electron micrographs of  grouper nervous necrosis virus particles
}}

'''''Betanodavirus''''', or '''nervous necrosis virus''' ('''NNV'''), is a genus of  [[Biology:Viral envelope|nonenveloped]] [[Biology:Positive-strand RNA virus|positive-strand RNA virus]]es in the family ''[[Biology:Nodaviridae|Nodaviridae]].''<ref>{{cite journal |last1=Sahul Hameed |first1=AS |last2=Ninawe |first2=AS |last3=Nakai |first3=T |last4=Chi |first4=SC |last5=Johnson |first5=KL |last6=ICTV Report |first6=Consortium |title=ICTV Virus Taxonomy Profile: Nodaviridae. |journal=The Journal of General Virology |date=January 2019 |volume=100 |issue=1 |pages=3–4 |doi=10.1099/jgv.0.001170 |pmid=30431412|doi-access=free }}</ref>  Member viruses infect fish and cause viral nervous necrosis (VNN) and viral encephalopathy and retinopathy (VER).<ref name="ViralZone">{{cite web|title=Viral Zone|url=http://viralzone.expasy.org/all_by_species/614.html|access-date=12 June 2015|publisher=ExPASy}}</ref> The genus contains four species.<ref>{{cite book|last=Cann|first=Alan|date=2001|title=Principles of Molecular Virology|url=https://books.google.com/books?id=wabARjhMBF8C&pg=PA871|publisher=Academic Press|pages=870–871|isbn=9780121585334|access-date=7 September 2020}}</ref>

==History==
Betanodaviruses were first reported between 1989 and 1991. They were linked with high mortality rates in young fish and were initially described as a [[Biology:Picornavirus|picornavirus]]-like virus. They were discovered around the same time in Australia, Norway, France and Japan.<ref name="Mori, K 1992">{{cite journal|last1=Mori|first1=Koh-Ichiro|last2=Nakai|first2=Toshihiro|last3=Muroga|first3=Kiyokuni|last4=Arimoto|first4=Misao|last5=Mushiake|first5=Keiichi|last6=Furusawa|first6=Iwao|year=1992|title=Properties of a new virus belonging to nodaviridae found in larval striped jack (Pseudocaranx dentex) with nervous necrosis|journal=Virology|volume=187|issue=1|pages=368–71|doi=10.1016/0042-6822(92)90329-N|pmid=1736540}}</ref><ref>{{cite journal |doi=10.1111/j.1365-2761.1990.tb00780.x |title=Picorna-like viral particles associated with mass mortalities in larval barramundi, Lates calcarifer Bloch |journal=Journal of Fish Diseases |volume=13 |issue=3 |pages=245–9 |year=1990 |last1=Glazebrook |first1=J. S |last2=Heasman |first2=M. P |last3=Beer |first3=S. W }}</ref><ref>Bloch, B., Gravningen, K. & Larsen, J. L. (1991). Encephalomyelitis among turbot associated with picornavirus-like agent. Diseases of Aquatic Organisms 10.</ref><ref>{{cite journal |doi=10.1016/0044-8486(91)90258-9 |title=Viral infection (picorna-like virus) associated with mass mortalities in hatchery-reared sea-bass (Dicentrarchus labrax) larvae and juveniles |journal=Aquaculture |volume=97 |issue=2–3 |pages=109–16 |year=1991 |last1=Breuil |first1=G |last2=Bonami |first2=J.R |last3=Pepin |first3=J.F |last4=Pichot |first4=Y }}</ref> The oldest evidence related to the virus, however, dates back to 1984 in Queensland (Australia) where a disease outbreak with the clinical signs and histopathological lesions corresponding to NNV was reported.<ref>MacKinnon, M.R. (1988). Rearing and growth of larval and juvenile Barramundi (Lates calcarifer)in Queensland. Paper presented at: Management of wild and cultured sea bass/barrumundi (Lates calcarifer) (Darwin, Australian Centre for International Agricultural Research)</ref>

==Virology==
===Structure===
[[File:Journal.ppat.1005203.g001.png|thumb|[[Engineering:Electron microscope|EM image]] and structure of grouper nervous necrosis virus (GNNV).]]
Viruses in the genus ''Betanodavirus'' are [[Biology:Viral envelope|non-enveloped]], with [[Icosahedral symmetry|icosahedral geometries]] and T=3 symmetry.<ref name="ViralZone" /> The diameter is around 37 nm. The virus-like particle contains 180 subunits of the capsid protein, and each capsid protein (CP) shows three major domains: (i) the N-terminal arm, an inter-subunit extension at the inner surface; (ii) the shell domain (S-domain), a jelly-roll structure; and (iii) the protrusion domain (P-domain) formed by three-fold trimeric protrusions.<ref name="Chen 2015">{{cite journal|last1=Chen|first1=Nai-Chi|last2=Yoshimura|first2=Masato|last3=Guan|first3=Hong-Hsiang|last4=Wang|first4=Ting-Yu|last5=Misumi|first5=Yuko|last6=Lin|first6=Chien-Chih|last7=Chuankhayan|first7=Phimonphan|last8=Nakagawa|first8=Atsushi|last9=Chan|first9=Sunney I|last10=Tsukihara|first10=Tomitake|last11=Chen|first11=Tzong-Yueh|year=2015|title=Crystal Structures of a Piscine Betanodavirus: Mechanisms of Capsid Assembly and Viral Infection|journal=PLOS Pathogens|volume=11|issue=10|pages=e1005203|doi=10.1371/journal.ppat.1005203|pmc=4619592|pmid=26491970|last12=Chen|first12=Chun-Jung |doi-access=free }}</ref>

=== Genomes ===
Genomes are linear, segmented, bipartite, and around 21.4kb in total length.<ref name="ViralZone" /> The genome is split in two segments RNA1 and RNA2 that together encode three genes.<ref name="Mori, K 1992" />

===Life cycle===
Viral replication is cytoplasmic. Entry into the host cell is achieved by penetration into the host cell. Replication follows the positive stranded RNA virus replication model. Positive stranded RNA virus transcription, using the internal initiation model of subgenomic RNA transcription is the method of transcription. Fish serve as the natural host. Transmission routes are passive diffusion and contact.<ref name=ViralZone />

== Disease ==

Betanodaviruses affect [[Biology:Teleost|teleost fish]]. A number of species are reported susceptible, more than 40 species, most of them marine.  Transmission routes are passive diffusion and contact.<ref name="ViralZone" /> The disease is more likely to occur in larvae or juveniles but it can also affect adults.<ref>{{cite journal|last1=Nakai|first1=T.|last2=Mori|first2=K.|last3=Sugaya|first3=T.|last4=Nishioka|first4=T.|last5=Mushiake|first5=K.|last6=Yamashita|first6=H.|year=2009|title=Current knowledge of viral nervous necrosis (VNN) and its causative betanodaviruses|journal=The Israeli Journal of Aquaculture – Bamidgeh|volume=61|issue=1–4|pages=198–207|doi=10.46989/001c.20559 |hdl=10524/19288|doi-access=free|hdl-access=free}}</ref>

== Clinical signs and lesions ==
[[File:Vacuoles_in_retina_of_Australian_bass_larva_experimentally_infected_with_NNV.jpg|thumb|Vacuoles in retina of [[Biology:Australian bass|Australian bass]] larva infected with NNV]]
Viral nervous necrosis can have a clinical or sub-clinical presentation. Signs include: abnormal behaviour like lethargy, anorexia, spiral swimming; and change in pigmentation. Mortalities of affected populations can be of up to 100%.<ref name="Arimoto1996">{{cite journal|last1=Arimoto|first1=Misao|last2=Sato|first2=Jun|last3=Maruyama|first3=Keigo|last4=Mimura|first4=Gen|last5=Furusawa|first5=Iwao|year=1996|title=Effect of chemical and physical treatments on the inactivation of striped jack nervous necrosis virus (SJNNV)|journal=Aquaculture|volume=143|issue=1|pages=15–22|doi=10.1016/0044-8486(96)01261-6}}</ref> Microscopical lesions are mostly located in brain, retina and spinal cord where necrosis of the neurons and the presence of round empty spaces called vacoules are commonly associated with the disease.{{cn|date=November 2022}}

==Evolution==
The most recent common ancestor of the four extant genotypes has been dated to ~1300 CE.<ref name=He2014>{{cite journal |doi=10.1016/j.ympev.2014.11.016 |pmid=25497669 |title=Divergence and codon usage bias of Betanodavirus, a neurotropic pathogen in fish |journal=Molecular Phylogenetics and Evolution |volume=83 |pages=137–42 |year=2015 |last1=He |first1=Mei |last2=Teng |first2=Chun-Bo }}</ref> An early reassortment event appears to have occurred in the early 1980s in Southern Europe.{{cn|date=November 2022}}

== Taxonomy ==
The following species are recognized:<ref name="ICTV">{{cite web|title=ICTV Report Nodaviridae|url=http://www.ictv.global/report/nodaviridae}}</ref>
* ''Barfin flounder nervous necrosis virus''
* ''Redspotted grouper nervous necrosis virus''
* ''Striped jack nervous necrosis virus''
* ''Tiger puffer nervous necrosis virus''

==References==
{{Reflist}}

==External links==
* [http://www.ictv.global/report/nodaviridae '''ICTV Report:''' ''Nodaviridae'']
* [http://viralzone.expasy.org/all_by_species/614.html '''Viralzone''': Betanodavirus]

{{fish disease topics|state=expanded}}
{{Baltimore classification}}

{{Taxonbar|from=Q16975146}}

[[Category:Nodaviridae]]
[[Category:Virus genera]]

{{Sourceattribution|Betanodavirus}}