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1. How to spot KHV
2. How KHV is spread
3. Preventing and controlling KHV
4. Response to Reports of KHV
5. Further information on KHV
6. Legislation relating to KHV

Koi herpesvirus (KHV) is a contagious viral disease of common carp (Cyprinus carpio) including mirror carp, leather carp, koi carp and ghost carp. It can cause high mortality.

Infected fish may not show clinical signs and the virus can persist in populations at low levels within populations. Disease outbreaks are typically triggered by stress and environmental conditions such as high temperature.ÌýÌýÌý

KHV is a listed disease (also known as a ‘notifiable’ disease) of both farmed and wild fish. Further information on KHV susceptible and vector species can be found in our guidance.ÌýÌý

KHV does not affect humans.

How to spot KHVÌý

KHV disease occurs at water temperatures between 16°C and 29°C. Stress events can trigger outbreaks. Affected fish often become lethargic and gather at water inlets or in the shallows.  Ìý

Signs of the disease can include: Ìý

• Patches of dead (necrotic) tissue in the gills, often with secondary fungal or bacterial infection. Gills may also appear pale  Ìý

• Sunken eyes Ìý

• Over or under production of mucus Ìý

• Rough, dry patches of skin Ìý

• Sloughing of mucus Ìý

• Appearance of bleeding on skin and base of fins Ìý

• Patchy pale colouration or reddening of the skinÌý

How KHV is spreadÌý

KHV is spread through contact with infected fish or water. The virus is released via faeces, urine, gills and skin.  Ìý

KHV can be spread through movements of infected fish, contaminated water, and contaminated equipment such as husbandry, angling and fish transport equipment. Ìý

Infected fish do not have to be sick or diseased to spread the virus.

Preventing and controlling KHVÌý

There is no treatment for KHV.ÌýÌý

Prevention is the best approach to disease control. You can protect your fish by being aware of the signs of KHV and other serious diseases and checking stock health regularly.ÌýÌý

Implement good husbandry and biosecurity practises. Further information on biosecurity measures plans, guidance and templates can be found here: Biosecurity Measure Plans - Information and Templates - °Ç¸ç³Ô¹Ï (www.gov.uk)Ìý

Do not buy fish of unknown origin. Follow the rules on importing, exporting or moving aquatic animals: Aquatic animal health and movements guides - °Ç¸ç³Ô¹Ï (www.gov.uk)Ìý

You must report suspicion or confirmation of KHV to the FHI immediately (by calling in England and Wales 01305 206700). This applies to fish showing clinical signs and test results indicating suspicion or presence of KHV, including those from healthy fish and environmental samples.

Response to Reports of KHV

The FHI will assess each report on a case-by-case basis and apply disease control measures if required. Ìý

KHV is endemic in Great Britain, meaning it is established in susceptible fish populations.Ìý

Statutory disease controls are applied to authorised aquaculture production businesses (APBs) and sites involved in fish movements (such as farms and importers). Controls may vary according to water(s) or type of facilities affected and the potential risk of disease spread.ÌýÌý

A different approach applies to recreational fisheries (see [link to KHV news article]. Outbreaks of KHV occur regularly every summer in carp populations in recreational fisheries and occasionally in ornamental varieties of carp such as koi carp in the ornamental trade in England and Wales. Hence from 2026, the FHI’s approach to KHV disease controls in recreational fisheries (also known as ‘put and take’ fisheries) in England and Wales has changed. This is in line with the FHI’s established proportionate, risk-based approach and reflects the endemic nature of the disease and evidence that statutory disease controls at these sites do not materially influence disease spread. Find out more on why these changes have been made and what they mean you and your business in the FHI’s news article.Ìý

For more information, please see the listed diseases and the disease status of England and Wales or the current confirmed disease outbreaks in England and Wales.

Further information on KHVÌý

KHV.Ìý

Legislation relating to KHVÌý

2009ÌýÌý

The listed diseases are in and .Ìý

The Cefas FHI Enforcement guidance explains the strategy and standards for how the FHI deliver enforcement to those they regulate under these and other relevant legislation.