''Cyprinid herpesvirus 3'' (also CyHV-3, koi herpes virus or KHV) is a species of virus causing a

viral disease A viral disease (or viral infection) occurs when an organism's body is invaded by pathogenic viruses, and infectious virus particles (virions) attach to and enter susceptible cells. Structural Characteristics Basic structural characteristics, s ...

that is very contagious to the

common carp The Eurasian carp or European carp (''Cyprinus carpio''), widely known as the common carp, is a widespread freshwater fish of eutrophic waters in lakes and large rivers in Europe and Asia.Fishbase''Cyprinus carpio'' Linnaeus, 1758/ref>Arkive The ...

''Cyprinus carpio''.

Pathology

It is most commonly found in ornamental

koi or more specifically , are colored varieties of the Amur carp ('' Cyprinus rubrofuscus'') that are kept for decorative purposes in outdoor koi ponds or water gardens. Koi is an informal name for the colored variants of ''C. rubrofuscus'' ke ...

, 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 ''Herpesviridae'' is a large family of DNA viruses that cause infections and certain diseases in animals, including humans. The members of this family are also known as herpesviruses. The family name is derived from the Greek word ''ἕρπειν ...

. 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. KHV is listed as a nonexotic disease of the EU, so is watched closely by the

European Community Reference Laboratory for Fish Diseases The European Community Reference Laboratory for Fish Diseases is located in Frederiksberg, Denmark at the National Veterinary Institute (a part of Technical University of Denmark). It is funded by the European Commission The European Commiss ...

. Symptoms of KHV include: * Gill

mottling Mottle is a pattern of irregular marks, spots, streaks, blotches or patches of different shades or colours. It is commonly used to describe the surface of plants or the skin of animals. In plants, mottling usually consists of yellowish spots o ...

* Red and white patches appearing on gills * Bleeding gills * Sunken eyes * Pale patches *

Blisters A blister is a small pocket of body fluid (lymph Lymph (from Latin, , meaning "water") is the fluid that flows through the lymphatic system, a system composed of lymph vessels (channels) and intervening lymph nodes whose function, like the ...

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.

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. However in 2020 this plan was found to be unlikely to work.

References

External links

Invading Species.com
Ontario Ministry of Natural Resources and the Ontario Federation of Anglers and Hunters
Koi Herpes Virus (KHV) Disease. Institute of Food and Agricultural Sciences Fact Sheet VM-149, University of Florida.

European Community Reference Laboratory for Fish Diseases

Carp herpesvirus - Managing Water Ecosystems - CSIRO
{{Taxonbar, from=Q386469 Carp Fish viral diseases Alloherpesviridae