Cyprinid herpesvirus 2
Species of virus
From Wikipedia, the free encyclopedia
Cyvirus cyprinidallo2, also known as Cyprinid herpesvirus 2 (CyHV-2) is a species of virus in the genus Cyprinivirus, family Alloherpesviridae, and order Herpesvirales.[1]
| Cyvirus cyprinidallo2 | |
|---|---|
Virus classification  | |
| (unranked): | Virus |
| Realm: | Duplodnaviria |
| Kingdom: | Heunggongvirae |
| Phylum: | Peploviricota |
| Class: | Herviviricetes |
| Order: | Herpesvirales |
| Family: | Alloherpesviridae |
| Genus: | Cyvirus |
| Species: | Cyvirus cyprinidallo2 |
| Synonyms | |
| |
CyHV2 can also be classified as herpesviral hematopoietic necrosis virus (HVHN) and infects goldfish (Carassius auratus) of all ages.[2][3] It can also infect the closely related species, Prussian Carp (C. gibelio) however koi and goldfish hybrids cannot be infected by CyHV2.[2] Outbreaks have been reported in both cultured and wild populations, and are highly lethal.[2]
Background
Genome
Whole genome sequencing revealed that the CyHV2 genome is 290,304 bp in size.[3] This number may be variable due to tandem reiterations.[3] Heterogeneous genome size is often observed in other species of herpesviruses.[3] These short yet complex tandem reiterations are most often seen in the terminal direct repeats; the most prevalent being the telomere-like repeats located towards the genome ends.[3] In comparison to the other viruses, the CyHV2 genome is the most complex in terms of the unique regions plus one copy of terminal direct repeats.[3]
HVHN has approximately 154 open reading frames (ORFs) and splicing between protein-coding regions affects 9 of these ORFs.[3] Five gene families have been identified. This included multiple genes from TNFR, ORF2, ORF25, RING, and ORF153, as well as ORF22, which is present as a family of two.[3]
Pathology
External symptoms of fish impacted with CyHV2 typically show pale patches localized at the gills but do not exhibit lesions.[2][5] Fish with this infection also appeared to be lethargic, anorexic, and exhibited a loss of appetite.[2][5] CyHV2 is more often characterized by internal symptoms such as an enlarged kidney and spleen, as well as pallor of the kidney.[2] Histopathology of infected goldfish has revealed tissue death in the hematopoietic tissues in both the kidney and the splenic pulp.[2] Necrosis was also observed in the pancreas.[2][4] Smaller, more scattered tissue death and swelling was also observed in the lamina propria as well as the submucosa of the intestine.[2][4]
At this time, disease prevention is mainly achieved by avoidance.[2] A formalin-inactivated vaccine developed in 2015 was effective against goldfish infected with HVHN, however, as of now, there is not an established timeline that discusses the duration of protection.[2][6]
