The Environment Agency and the Centre for Environment, Fisheries and Aquaculture Science (Cefas) are investigating outbreaks of Koi herpesvirus (KHV) disease at three stillwater fisheries in the South and East of England. These are the first KHV mortalities recorded this year in fisheries and the most serious cases in terms of losses since the disease was first recorded in the UK.
In order to help prevent further spread of the disease the Environment Agency will not, until further notice, be permitting any live fish movements off the affected sites. The Agency is working closely with Cefas to find the source of the outbreak and identify any further sites that may be infected.
KHV is not currently one of the diseases subject to specific control measures under EU legislation. However, the disease has been included in the list of non-exotic diseases that will be subject to control on a Community-wide basis in the proposal for a new Council Directive on animal health requirements for aquaculture animals currently being negotiated in Brussels.
KHV has no implications for human health. KHV is a contagious disease of common carp mainly recorded in ornamental species such as Koi. A variety of symptoms of the disease have been reported including lethargy. The fish may produce excess mucus and often show rough pale patches of the skin. In addition the gills are normally affected, typically showing necrotic patches on the gill filaments. The virus has the ability to remain latent in the host for long periods of time, becoming active only at permissive temperatures.
The disease occurs at temperatures of between 15C and 28C. There is no treatment and mortalities are invariably high, between 50% and 95%. There have been a number of isolated incidences of the disease in the UK since 2000 but this latest outbreak appears to be the more serious. KHV has been confirmed in several other countries in Europe and other parts of the world.
KHV is not currently a notifiable disease within the EU or UK. However, it has recently been added to the list of disease to be notified to the World Organisation of Animal Health (the OIE).
Pending the possible control of the disease under new measures in the final stages of negotiation in the EU, those in the industry responsible for importing fish species susceptible to KHV should make every effort to identify healthy, disease free sources of stock.
Defra is funding, in partnership with industry organisations, a number of projects on KHV including programmes for improving diagnostic tests and the development of non-lethal screening tests to avoid the destruction of valuable adult fish. We also funded an international workshop on KHV in 2004 to bring together world experts and raise the profile of the disease.
For more information on KHV contact the CEFAS Fish Health Inspectorate: firstname.lastname@example.org or the Environment Agency, National Fisheries Laboratory, Brampton: email@example.com
Meanwhile the first round of testing for Viral Haemorrhagic Septicaemia (VHS) virus on fish farms (see Aquafeed.com article) within the Yorkshire Ouse designated area has proved negative. A second round of testing is currently in progress and results are expected by mid July.