Phylogenetic characterization of Polish isolates of infectious pancreatic necrosis virus in salmonid fish

Introduction Infectious pancreatic necrosis virus belongs to the genusAquabirnavirusand familyBirnaviridae. By VP2 gene similarity, aquatic birnavirus is clustered into seven genogroups. The aim of this study was to genetically analyse IPN viruses occurring on Polish fish farms. Materials and Methods Samples from freshwater fish mostly from 2012 to 2013 and from northern Poland were examined for the presence of IPN virus using isolation on cell cultures, real-time RT-PCR and RT-PCR. Fragments of 1,377 and 1,079 bp of the VP2 and VP5 genes, respectively, were sequenced, and the results were assembled into one consensus and analysed by Geneious software. The same VP2 gene region was compared and a phylogenetic tree generated by the neighbour-joining method and MEGA6 software. Results All tested Polish isolates belonged to genogroup 5, like other European Spajurup isolates. Conclusion Our findings prove that there is only one IPN virus genogroup in Poland. Polish isolates show close relationships with each other. There is a close relationship between Polish isolates and isolates from Turkey, Spain and Iran. Isolate 57 is a separate branch related to isolates from the United States and Taiwan. This points to the likelihood of past virus introduction via import of stock from those countries.