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National Reference Laboratory for West Nile virus (WNV)

Information of the FLI on the current WNV Situation

West Nile virus (WNV

West Nile fever virus (WNV) is an emerging arthropod-borne flavivirus. WNV is an important zoonotic virus (infections of humans can cause encephalitis with fatal outcome) with its major reservoir in the wild bird population. There is no evidence for the introduction of live WNV, a future introduction cannot be ruled out in principle, also in the light of an increasing climate warming and the already existing presence of the main mosquito vectors for WNV (Culex pipiens spp.) in the south of Germany.

At the same time the outbreak from WNV in wild birds in Austria, autumn 2008, and horses in Italy 2008 and 2009 shows that the virus spreads further northward. Also in 2009 the active surveillance program was continued by the analysis of hundreds of samples from wild birds and horses. We found WNV specific antibodies in migratory birds (middle and long distance) but not in resident birds, domestic poultry or in local horse population. WNV-specific nucleic acid could not be found in any of the samples.

Since May, 2009 a conventional killed vaccine (Innovator® Fort Dodge) is admitted for the application by horses in Germany. Therefore, in the NRL the first follow-up study was carried out to determine the antibody titres of horses after vaccination by the neutralization assay. For the improvement of the diagnostics, especially for the application as a screening procedure and for the application with very low sample volume (in particular from wild birds) an indirect ELISA on the base of recombinant protein was developed. At the same time two commercial ELISA`s for the detection of WNV antibodies under registration for the national licensing.