Mosquitoes collected in Germany in 2016, including Culex pipiens pipiens biotype pipiens, Culex torrentium and Aedes albopictus, as well as Culex pipiens pipiens biotype molestus (in colony since 2011) were experimentally infected with Zika virus (ZIKV) at 18 °C or 27 °C. None of the Culex taxa showed vector competence for ZIKV. In contrast, Aedes albopictus were susceptible for ZIKV but only at 27 °C, with transmission rates similar to an Aedes aegypti laboratory colony tested in parallel.

Mosquito-specific viruses (MSVs) are a subset of insect-specific viruses that are found to infect mosquitoes or mosquito derived cells. There has been an increase in discoveries of novel MSVs in recent years. This has expanded our understanding of viral diversity and evolution but has also sparked questions concerning the transmission of these viruses and interactions with their hosts and its microbiome. In fact, there is already evidence that MSVs interact with the immune system of their host. This is especially interesting, since mosquitoes can be infected with both MSVs and arthropod-borne (arbo) viruses of public health concern. In this review, we give an update on the different MSVs discovered so far and describe current data on their transmission and interaction with the mosquito immune system as well as the effect MSVs could have on an arboviruses-co-infection. Lastly, we discuss potential uses of these viruses, including vector and transmission control.

The interplay between arthropod-borne (arbo) viruses and their vectors is usually complex and often exert unique relationships. Aedes japonicus japonicus (Hulecoeteomyia japonica or Ochlerotatus japonicus japonicus), an invasive mosquito species with laboratory proven vector competence for a number of emerging viruses has been newly introduced to Germany and is currently expanding its range throughout the country. On the other hand, West Nile virus (WNV), an emerging arbovirus originating from Africa, is already circulating in several European countries and might soon be introduced to Germany. Because newly introduced and rapidly expanding vector species pose a potential risk for public health in Germany, we assessed the vectorial capacity of German Ae. j. japonicus populations for WNV and Japanese encephalitis virus (JEV). The results indicate that German Ae. j. japonicus are susceptible for JEV but are refractory to infection with WNV. Of 67 Ae. j. japonicus females challenged by feeding of WNV-containing blood, none had measurable amounts of WNV-RNA (0% infection rate) on day 14 post-infection. In contrast, all females challenged with JEV were positive for JEV-RNA (100% infection rate) on day 14 post-infection. The reason for WNV resistance remains to be determined but is independent from co-infection with other flaviviruses or the presence of endosymbiotic Wolbachia, since we found no evidence for other flavivirus infections within 1,033 tested A. j. japonicus females from the sampling region, nor detectable Wolbachia infection within 30 randomly selected individuals.