Koi Herpesvirus: Welfare Crisis in Pond Fish

Koi herpesvirus is a devastating infectious disease affecting koi carp and common carp, with mass mortality events causing acute welfare suffering and posing biosecurity challenges for fisheries and garden ponds.

Key Facts

Koi herpesvirus (KHV) can kill 80-100% of infected fish populations within days to weeks
The virus is triggered by specific water temperatures (16-25 degrees Celsius), causing seasonal outbreaks
KHV is a notifiable disease in the UK, requiring mandatory reporting to the Animal and Plant Health Agency
Infected fish show gill damage, respiratory distress, sunken eyes, and patchy skin discolouration
The virus has spread globally through the ornamental fish trade and affects wild carp populations

Welfare Considerations

KHV causes severe and rapid welfare suffering. Fish experience progressive respiratory failure as gill tissue is destroyed, leading to hypoxia and distress before death. Mass mortality events leave survivors in heavily contaminated water with deteriorating conditions. There is currently no approved treatment for KHV in the UK. Prevention through strict biosecurity, quarantine of new fish before introduction, and avoiding the use of water from infected sources is the primary welfare protection measure.

What You Can Do

Quarantine new fish for at least four weeks before introducing them to existing pond populations
Never release pond fish or water into wild waterways to prevent disease spread
Report suspected KHV mortality events to the Centre for Environment Fisheries and Aquaculture Science
Support research into KHV vaccines and biosecurity improvements in the aquaculture sector