Cyprinid herpesvirus 3

Cyprinid herpesvirus 3 (also CyHV-3, koi herpes virus or KHV) is a species of virus causing a viral disease that is very contagious to the common carp Cyprinus carpio.

Cyprinid herpesvirus 3
Virus classification
(unranked): Virus
Realm: Duplodnaviria
Kingdom: Heunggongvirae
Phylum: Peploviricota
Class: Herviviricetes
Order: Herpesvirales
Family: Alloherpesviridae
Genus: Cyprinivirus
Species:
Cyprinid herpesvirus 3
Synonyms

CyHV-3
Koi herpes virus
KHV

A platinum Ogon koi, with skin reddening due to Cyprinid herpesvirus 3 infection

Pathology

It is most commonly found in ornamental koi, which are often used in outdoor ponds or as feeder stock. The first case of KHV was reported in 1998, but not confirmed until later in 1999.

KHV is a DNA-based virus. After discovery, it was identified as a strain of herpesvirus. Like other strains, KHV stays with the infected fish for the duration of their lives, making the recovered and exposed fish potential carriers of the virus. Koi fish infected with KHV may die within the first 24–48 hours of exposure. The virus is found in 33 countries.[1]

KHV is listed as a nonexotic disease of the EU, so is watched closely by the European Community Reference Laboratory for Fish Diseases.

Symptoms of KHV include:

  • Gill mottling
  • Red and white patches appearing on gills
  • Bleeding gills
  • Sunken eyes
  • Pale patches
  • Blisters

Changes in the specimen's behaviour may also indicate the presence of KHV. Behavioural symptoms may include disorientation, hyperactivity and potentially isolation, in which the specimen detaches themselves from the shoal.[2]

Use as a biological control agent

In 2016 the Australian Government announced plans to release the virus into the Murray-Darling basin in an attempt to reduce the number of invasive common carp in the water system.[3][4] However in 2020 this plan was found to be unlikely to work.[5]

References
  1. Thistleton, John (13 June 2016). "Millions of Lake Burley Griffin carp face swift death from cyprinid herpesvirus release". The Canberra Times. Fairfax Media. Archived from the original on 13 June 2016.
  2. "Koi Herpesvirus - KHV". Somis Koi. Retrieved 2020-08-13.
  3. Kilvert, Nick; Thomas, Kerrin (1 May 2016). "Herpes virus to be used in fight against carp in Murray River, Christopher Pyne says". ABC News. Australian Broadcasting Corporation. Archived from the original on 5 May 2016.
  4. "Carp herpesvirus". Managing Water Ecosystems - CSIRO. 2018-04-26. Retrieved 2020-11-09.
  5. Mintram, Kate S.; Oosterhout, Cock; Lighten, Jackie (2020-10-14). Knutie, Sarah (ed.). "Genetic variation in resistance and high fecundity impede viral biocontrol of invasive fish". Journal of Applied Ecology. Wiley. doi:10.1111/1365-2664.13762. ISSN 0021-8901.
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