Koi Herpes Virus (KHV)

Koi Herpes virus is extremely infectious. It takes as little as ten minutes of exposure to infect a Koi. Although, the virus can only live 24 hours without a host. Goldfish are not susceptible to Koi Herpes Virus. Even the Koi/Goldfish hybrids are usually immune too. Koi Herpes Virus (KHV), is also know as Carp Gill Necrosis Virus. There are two reasons for the different names:

  • The virus affects all types of Cyprinus carpio, it is not limited to Koi only.
  • Scientists are still not sure that this virus is a true Herpes Virus (Herpes viruses can lay dormant for years before an outbreak is triggered, usually by immunosuppressant conditions like stress).


Koi Herpes Virus History

In the spring of 1998, large amounts of food carp and ornamental Koi started to die in farms in Israel. This mysterious virus spread all over Israel and then eventually into other parts of the world, due to unregulated trade. Carp Gill Necrosis Virus has cause tens of millions of dollars in damage ever since the first outbreak nearly ten years ago. In the fall of 2003, Lake Kasumigaura and Lake Kitaura in Japan experienced a KHV outbreak. $2.55 million dollars were lost in a week alone. The food carp industry in Japan is still trying to recover, for supply is still very low because those two lakes were the largest producers of carp.


The symptoms of Koi Herpes Virus are:

  • Fatigue
  • Gill Necrosis
  • Gasping at the Surface
  • Increased Mucus Secretion
  • Sunken Eyes
  • Pale Patches of Skin


KHV Spread and Control

When there is an outbreak of Koi Herpes Virus, there is usually a 80%-90% mortality rate in a pond. It takes a Koi about 3 weeks to develop a sufficient amount of antibodies in order to fight off the virus. Unfortunately, Koi Herpes Virus is deadly enough to kill a Koi within a week of initial exposure. This can be combated by raising the water temperate above 86 degrees Fahrenheit for a month in order to suppress the virus long enough for enough antibodies to develop. Although, if KHV is a herpes virus, an "immunized" Koi will infect any other Koi with no prior exposure and then a massive die off will ensue.


If you believe that you have had an outbreak of Koi Herpes Virus in your pond, contact a local veterinarian that is knowledgeable in Koi health. Several Koi may be needed for sacrifice in order to obtain good samples for PCR testing.


KHV Prevention Information for Koi Keepers


The best way to prevent an outbreak of Koi Herpes Virus in a pond is QUARANTINE. Quarantine is the #1 proven method to stop the spread of disease. New Koi should be quarantined for a minimum of 3 weeks at 75 degrees Fahrenheit before they can be released into the general population.


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