KHVD Occurrence, Diagnosis, Control, Research and Future
in the Netherlands and Europe

Marc Y. Engelsma and Olga L.M. Haenen

CIDC-Lelystad, Fish and Shellfish Diseases Laboratory
P.O. Box 2004, 8203 AA Lelystad, The Netherlands

ABSTRACT

In recent years, koi herpesvirus disease (KHVD) has quickly spread over Europe. In several European countries the first KHVD cases were observed in 2002 (Italy, Denmark) and 2003 (France, Austria, Switzerland). In contrast to Western Europe, where koi and carp are mainly kept as ornamental fish, in Eastern Europe carp is farmed for consumption and KHVD could have a huge impact on the carp industry. At the moment however, Eastern Europe still seems free from KHVD. However, common carp exported from Poland to Germany were shown to be KHV positive.

The highest incidence of KHVD cases in Europe is found in Germany, England and the Netherlands. Germany has had over 250 cases since 2002. England had 36 cases in 2002, and more cases followed in 2003. In the Netherlands a steady increase was seen from 2 KHV positive cases in 2001 up till 27 cases in 2003. Concern for these countries is that KHVD could possibly not only be restricted to koi-trading and private ponds but already be spread into the natural environment. At the moment however, there is still no evidence for this. As KHVD is not notifiable for the EU, the control on spread of the disease within the EU is minimal.

The majority of the KHV cases in the Netherlands were detected by PCR (Gilad et al., 2002), with or without using gill histopathology as a confirmatory method. In a few cases the herpes virus could be cultured successfully on Epithelioma Papilloma Carposum (EPC) or Koi Fin-1 (KF-1) cells. In 2001, we succeeded in isolating the virus for the first time in the Netherlands from a clinical diseased koi. The inoculated sample of gills and pooled internal organs showed cytopathic effect (CPE) at the 2nd passage of EPC cells.

Unfortunately, the sensitivity of viral isolation is inadequate for diagnostics of KHV. Additional methods, as PCR, are required to correct diagnosis of the disease. Currently effort is put into developing alternative detection methods as immunoflourescence tests (IFT) to support diagnostics of KHVD.