Koi Herpes Virus

Koi Herpesvirus (KHV) is a very damaging and easily spread virus that affects common carp and carp varieties such as koi Fish. Koi Herpesvirus (KHV) represents a third cyprinid herpesvirus formally designated Cyprinid herpesvirus 3(CyHV-3). Other nomenclature (Carp Interstitial Nephritis and Gill Necrosis Virus (CNGV)) has been suggested. Koi Herpes Virus is not new. It has been around for decades, even before we knew what it was. Koi were said to have a sleeping disease or some other explanation.



Outbreaks of the disease occur in summer, when water temperatures are high, and can kill between 20% and 100% of carp in a fishery. The disease is most likely to be spread when fish are stocked. But it is also possible that the virus could be moved on fishing tackle. To protect your fishery, or the place you fish, there are practical steps you can take.

If your fishery has an outbreak of the disease, there are also actions you can take to reduce the losses and ensure that the fishery can recover as quickly as possible. You can also take action to prevent problems in the future.

The virus will spread from one koi to the next only when the infected koi is “shedding” the virus. By shedding I mean producing and releasing the virus from its body. It is possible for an infected koi to not be shedding the virus and not spread it to another koi. It is also possible for a koi to have briefly come in contact with the virus, develop antibodies to the virus, but never contract the virus. This is why 100% accurate testing is difficult to achieve.


No KHV quarantine or testing procedure offers 100% assurance a koi previously infected with KHV will be detected. Through quarantine and serological testing we can greatly reduce the odds of infecting other koi. Serological technology is available to measure antibodies to the KHV virus. Both Enzyme Linked Immunosorbant Assay (ELISA) and the Virus Neutralization Antibody Assay (VN) serologies are available at modest cost, the latter being the most sensitive. The KHV disease outbreak illustrated in the photos should have been prevented by testing the fish for the carrier state while in quarantine.

Serology done on survivors strongly suggests some imports had survived a previous KHV infection as they carried low antibody titers. It is unclear how long a KHV survivor will maintain detectable antibodies but studies are in progress. The CEFAS group has demonstrated detectable antibodies a year or more following infection. Using serology on fish in quarantine is another tool we have available for protecting our collections.

If a fish has detectable levels of antibodies to KHV, it has been previously infected and must be considered a carrier. Carriers have the potential to shed the virus at a later time, infecting other fish. Materials and procedures we find useful for drawing blood for anti KHV antibody testing are outlined.



Source:
http://www.simikoi.com/subcat421.html
http://www.koihealth.org/