Emerging vesiculo-type virus infections of freshwater fishes in Europe

International audience; Rhabdoviruses were isolated from perch Perca fluviatilis and largemouth bass À,fi'croptertts salmoides exhibiting clinical signs of disease, Preliminary studies indicated that these viruses could be neutralised by antisera to perch rhabdovirus (Dorson et al. 1984) and may be similar to those previotrsiy isolated from grayling Thymallus thymallus and pike-perch Stizostedion stizostedion.The relationship between these viruses and the previously characterised fish rhabdoviruses, pike fry rhabdovirus (PFRV), spring viraemia of carp virus (SVCV) and lake trout rhabdovirus, was investi- Eated. Viruses were propagated in bluegill fry (BF-2) cells and were characterised using electron microscopy, serum neutralisation tests, immunofluorescence tests, sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and nucleotide sequence analysis. The bullet-shaped viral particles appeared to be compact, with spikes visible at the surface, a morphology similar to that of the vesiculovirus group of rhabdoviruses. Serum neutralisation tests showed that the viruses were antigenically closely related to the previously characterised perch rhabdovirus, but were not significantly neutralised by antisera to PFRV, SVCV or viral haemorrhagic septicaemia virus (VHSV), In immunofluorescence tests with perch rhabdovirus antisera, strong specific fluorescence was observed in cell cultures infected with the new rhabdovirus isolates, but no fluorescence was observed with antisera to PFRV, SVCV or VHSV. SDS-PAGE analysis reveaied a polypeptide profile typical of vesiculoviruses, but the novel virus isolates had different relative mobilities of their P and M proteins compared to PFRV and SVCV. Nucleotide sequence analysis was carried out using reverse transcriptase-polymerase chain reaction (RT-PCR) and DNA sequencing of a 439 base-pair region of the viral L gene. The novel rhabdovirus isolates had 95o/" identity to perch rh.abdovirus. Phylogenetic analysis using both maximum parsimony and neighbour-joining methods assigned the perch rhaboviruses to a separate group to that of PFRV, SVCV and lake trout rhabdovirus, These data are the initial characterisation of a group of emerging fish vesiculo-type viruses that are biochemically and geneticaliy distinct from the PFRV, SVCV and lake trout rhabdoviruses.