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The Distribution of KHV in England and Wales 2007- 2008

by the Fish Site Editor
09 June 2009, at 1:00am

Koi HerpesVirus (KHV) causes a highly virulent disease affecting carp (Cyprinus carpio) and poses a serious socio-economic threat to the UK carp industry, writes Nick Taylor, Keith Way, Peter Dixon, Edmund Peeler, Keith Jeffery & Kevin Denham - Cefas.

From analysis of archive histological material, Cefas has putative evidence for the presence of KHV in England since 1996. However, until 2003, KHV had only been detected and isolated from sites in the UK holding ornamental carp imported from Israel, Malaysia, USA and Japan. In 2003 Cefas detected KHV in common carp during investigations into large mortalities in angling waters. Further detections of KHV were subsequently made at a small number of angling waters in 2004 and 2005. In 2006 KHV disease outbreaks were reported and confirmed at 23 sites in southern England.

KHV disease has been made an OIE listed disease and became a notifiable disease in England and Wales in April 2007. KHV is also listed under Council Directive 2006/88/EC, thus subjecting the disease to community controls. All EU member states had to submit their health status with regard to KHV by 1st August 2008. As a result the geographic distribution and prevalence of KHV in England and Wales needed to be assessed in order to determine the UK’s status and the practicality of different statutory control options under consideration by Defra. This Defra-funded study aimed to assess:

  1. The types of fish that have been exposed to KHV – ornamental, fishery and farmed.
  2. The geographic distribution and prevalence of the infection within each sector For further information, the full report and an associated “Questions and Answers” document are available on the efishbusiness website (http://www.efishbusiness.co.uk/news/080902a. pdf). The summary is reproduced below:

Summary

This study aimed to determine the geographic distribution and prevalence of KHV in England and Wales in order to determine the practicality of different statutory control options under consideration by Defra. Carp were tested for the presence of KHV antibodies in their blood using an Elisa method. The study examined carp from 82 farm sites, 71 fisheries and 12 consignments of ornamental carp imported from seven different S.E. Asian countries.

Three of the farms sampled produced positive results. These results suggest that UK fish farms are a relatively safe source from which to obtain fish. Fish farms do, however, have the potential to spread the virus rapidly due to the number of contacts they make. Consequently it is of great importance that infected farms are detected early and steps taken to prevent spread.

As the primary aim of the study was to establish the geographic distribution of KHV exposed fish, those fisheries deemed to be at highest risk of exposure were sampled. These were sites receiving high numbers of consignments of fish, or suffering mortalities. Of the 71 fisheries tested, 26 were positive. The results indicate that none of the geographic areas studied were KHV free.

Consignments of imported fish from six countries tested positive for KHV antibody. Although a high proportion of consignments were positive, the results indicate that lower risk stocks of fish exist that could be sourced by the industry.

Although widespread and prevalent in ‘highrisk’ fisheries, there are good prospects for KHV control as our farms appear to relatively free of the virus, and there are low risk stocks of fish from third countries that could be sourced. Additionally, similar controls to those in place for SVC may be effective at controlling KHV in fisheries.

June 2009

the Fish Site Editor