Culex pipiens and Culex torrentium populations from Central Europe are susceptible to West Nile virus infection

West Nile virus (WNV), a Flavivirus with an avian primary host, is already widespread in Europe and might also pose an infection risk to Germany, should competent mosquito vectors be present. Therefore, we analysed the ability of WNV to infect German Culex mosquitoes with special emphasis on field collected specimens of Culex torrentium and Culex pipiens biotype pipiens. We collected egg rafts of Culex mosquitoes over two subsequent seasons at two geographically distinct sampling areas in Germany and differentiated the samples by molecular methods. Adult females, reared from the various egg rafts, were challenged with WNV by feeding of artificial blood meals. WNV infection was confirmed by real-time RT-PCR and virus titration. The results showed that field collected C. pipiens biotype pipiens and C. torrentium mosquitoes native to Germany are susceptible to WNV infection at 25 °C as well as 18 °C incubation temperature. C. torrentium mosquitoes, which have not been established as WNV vector so far, were the most permissive species tested with maximum infection rates of 96% at 25 °C. Furthermore, a disseminating infection was found in up to 94% of tested C. pipiens biotype pipiens and 100% of C. torrentium. Considering geographical variation of susceptibility, C. pipiens biotype pipiens mosquitoes from Southern Germany were more susceptible to WNV infection than corresponding populations from Northern Germany. All in all, we observed high infection and dissemination rates even at a low average ambient temperature of 18 °C. The high susceptibility of German Culex populations for WNV indicates that an enzootic transmission cycle in Germany could be possible

Additional file 2: Table S2. of Host-feeding patterns of mosquito species in Germany

Kruskal-Wallis tests on the differences of the percentages of detected birds, non-human mammals and humans between the three land use classes (natural, rural and urban) for the three most frequent mosquito species (Fig. 3). (DOCX 14 kb

Additional file 3: Table S3. of Host-feeding patterns of mosquito species in Germany

Chi-square tests on the differences in the frequencies of detected mammalian or avian hosts among all pairs of used trapping methods with adjusted P-values for multiple comparisons. (DOCX 13 kb

Additional file 1 of Interaction of Mesonivirus and Negevirus with arboviruses and the RNAi response in Culex tarsalis-derived cells

Additional file 1: Table S1. List of primers used 5′ to 3′