KHV has been a problem in both Koi Carp and Common Carp in the UK since 1996. Although it does not appear to affect other cyprinids such as goldfish and grass carp, the virus DNA has been detected in their tissues. Whether other cyprinids which are harboring the virus in their tissue can then infect in-contact Common Carp has not yet been definitively established, this risk cannot be ruled out. There are two separate strains of the virus, a European strain and an Asian strain.
There is now no doubt that KHV seems to be on the increase in the Coarse Fish Industry, with resultant major mortality issues as well as the Regulatory problems that accompany a Listed (Notifiable) Disease. This classification also extends to KHV in Koi Carp kept by hobbyists – the confirmed presence of KHV in either a coarse fish site or in a Koi Carp keepers pond must be notified to CEFAS who will then decide what action they will take as a result.

Email: fhi@cefas.gov.uk
Telephone: 01305 206700
Monday to Thursday – 9am to 5pm, Friday 9am to 4:30 pm

KHV can affect fish of various ages, often resulting in 80–100 per cent mortality in susceptible populations when water temperatures are between 60° and 77°F (16° and 25 °C). However, as with other Herpes viral infections in a variety of species, KHV may remain in the infected fish for life; therefore, fish that recover from a KHV outbreak should be considered as carriers of the virus, and under certain circumstances will release the virus which can then infect other naïve in-contact fish.
One of the challenges with this virus is in establishing if a water body is infected in the absence of any clinical signs in the inhabitant fish. This is where a KHV eDNA test kit can be very valuable. Without the need to involve the actual fish it can determine if the water itself is infected with KHV. However, although a positive result 100% confirms that KHV is present in the water, a negative result simply demonstrates that the test has not been able to find the KHV DNA, it does not mean that the water is free of the virus.