Most Australian Koi hobbyists have heard something about KHV. To date, KHV is not known to be or have been established in Australia in Koi or European Carp. Nor is it known to have been temporarily introduced into wild, hobby or commercial stocks. The purpose of this article is to give a basic introduction to the virus. It must be stressed that we do NOT have the virus in Australia. The current import ban on Koi into Australia has been our best defense. In the interest of maintaining this effective prevention method it is my own personal opinion that the import ban should continue. Likewise, any efforts to import Koi illegally into Australia should be openly discouraged.

KHV or Koi herpes virus is also known as Cyprinid herpsvirus-3 (CyHV-3). A highly contagious virus affecting Koi and carp (Cyprinus carpio), it may cause up 100% mortality within infected populations. Other fish species, including goldfish are not known to be affected or become carriers.

Infection can produce gill lesions and high mortality. Gills are the most commonly affected part of Koi with necrotic patches. Other external signs include gill mottling with red and white patches. This looks similar to columnaris disease. There is also bleeding of the gills, sunken eyes, pale patches or blisters on the skin, excessive mucus shedding and dry feeling skin. There can also be secondary bacterial and parasitic infections. These can mask the signs of KHV infection. Deaths normally start to occur within 24-48 hours of clinical signs. The behavior in infected Koi include; remaining near the surface, lethargy, breathing distress, stopped feeding and erratic swimming.

Koi become infected via direct contact, exposure to infected body fluids or water. Once infected, the fish may either die or become a carrier.

There is currently no treatment for KHV. Exposed survivors are known to spread the disease to non-infected Koi. There is no vaccine available to date. However, research in Israel appears promising.

Due to the highly contagious nature of KHV and the risk of infection from survivors, owners of affected populations are advised in all countries with the disease to complete a humane euthanasia of the entire pond population as a control measure and prevent possible future infection. This must be followed up with disinfection of all materials and systems that have been in contact with the infected fish.

In Australia, the most effective means of prevention is to continue the ban on imports of Koi and carp. Any illegal importation of Koi remains a great risk to the Australian Koi hobby. While the effective quarantine of all new fish is the most dependable method of disease prevention, there is not currently a 100% reliable method of determining if a non-infected Koi is a potential carrier. Nil imports remain the best defense against infection. I cannot stress this strongly enough

References:

Koi Herpes Virus (KHV) Disease Fact Sheet VM- 149; University of Florida - June 2004

Written by Bradley Bradley on behalf of the KSA Executive Committee