[Characterization of viral hemorrhagic septicemia (VHS) virus isolates in trout]

Virus diseases of fish can seriously impair the economy of aquacultur. Control and prevention of fish diseases in the European Union (EU) are focussed on the viral haemorrhagic septicaemia (VHS) and the infectious haematopoeitic necrosis (IHN). The diagnosis of VHS and IHN is performed in the Federal Republic of Germany (FRG) on the basis of the legislation of the EU. Since 1994 we received an increasing number of VHS virus (VHSV) isolates which did not react with a commercially available anti-VHSV monoclonal antibody (MAb) in the indirect immuno fluorescence test. With our own MAb ID8, however, as well as with additional diagnostic methods these virus isolates could be identified. These isolates of rainbow trouts were designated as VHSV type "Wi". Electron microscopically all stages of rhabdovirus maturation could be detected. Morphologically the isolates were undistinguishable from other rhabdoviruses. By immuno electron microscopy using the MAb ID8 rhabdovirus nucleocapsid structures were demonstrated. The virulence of the new VHSV type Wi was not different from that of a VHSV isolate with conventional reaction patterns as well as of a VHSV laboratory strain.