Understanding Koi Herpesvirus Disease
Koi Herpesvirus (KHV) is a significant viral infection affecting fish, particularly common and ornamental carp species (Cyprinus carpio). This disease is officially recognised in the United Kingdom and poses a serious threat, often leading to substantial mortality rates among affected populations. The symptoms of KHV typically manifest when water temperatures are maintained between 16 to 28 °C, with affected fish displaying distinct signs including:
- Necrotic patches (either white or brown) on the gills
- Rough patches on the skin accompanied by sloughing mucous
- Sunken eyes
If there is any suspicion of a KHV outbreak, it is imperative to contact the Fish Health Inspectorate (FHI). This includes observing the aforementioned symptoms or noting any deaths among carp or carp hybrids. It is essential to highlight that KHV does not pose any risk to public health.
Immediate Action Required Post-Outbreak
Following the identification of KHV disease, affected sites must engage in a formal monitoring programme. The FHI will conduct visits to these locations to seek evidence of the disease and ensure compliance with existing statutory controls. In the event that a notifiable disease is confirmed, the FHI will implement specific measures aimed at curbing the spread of the infection, known as confirmed designations.
The following restrictions are imposed under these disease control measures:
- No movement of any aquatic animals, including eggs and gametes, is permitted without prior written consent from the FHI, whether into, out of, or within the confirmed designation area.
- Dead aquatic animals, alongside their eggs and gametes, must be disposed of through an approved method in accordance with local Environmental Health department regulations.
- Any recurrences of mortality or spread to other waters within the designated area must be reported to the FHI immediately.
- Site operators must notify the FHI in advance of any planned physical alterations to the site, including changes to boundaries, water size or number, and overall usage. Written permission from the FHI is required before making such changes.
All requests for consents under the Confirmed Designation Notice must be submitted to the FHI with at least five working days’ notice.
Protocol for New Outbreaks
Upon laboratory confirmation of KHV disease at a site, the FHI enforces statutory controls to prevent further dissemination of the virus. These measures specifically restrict the movement of aquatic animals within the affected area.
As of now, disease controls have been established at several locations, including a growing facility in Tree Farm, Aspley Guise, Milton Keynes, since 10 September 2026. Conversely, certain disease controls have also been lifted in other areas.
For those interested, there are resources available to view all KHV disease outbreaks, their geographical locations, and the corresponding control measures in place. Additionally, information on how to prevent the introduction and spread of KHV disease can also be accessed.
Background on KHV Disease Regulations
Koi Herpesvirus disease is classified as a listed disease under The Aquatic Animal Health (England and Wales) Regulations 2009, with outbreaks being subject to regulatory controls in the UK since 2007. The UK implements a comprehensive surveillance programme for this disease.
When the FHI confirms an outbreak, they undertake necessary actions to manage and, where feasible, eradicate the disease. This may involve imposing movement restrictions on susceptible species in the affected vicinity, enhancing biosecurity measures, culling infected fish, and undertaking thorough cleaning and disinfection of the premises.
Once statutory controls are in effect, site operators must formally request permission from the FHI to move live fish into, out of, or within the designated area, as well as to make significant alterations to site operations. This requirement extends to fish eggs and gametes as well.