Is Rift Valley fever virus a threat for Germany? Evaluation of the vector competence of German mosquitoes for Rift Valley fever virus

Rift Valley fever virus (RVFV; family Phenuiviridae) is transmitted by different mosquito species. The virus is prevalent in Africa and the Middle East. European countries may also be at risk due to passive movement of infected vectors through flights. To investigate the vector competence of German mosquitoes for RVFV, two German lab colonies of Culex pipiens biotype molestus from Hesse (CPM; n=306) and Aedes albopictus from Freiburg (AA; n=207) were offered heparinized bovine blood mixed with 107 TCID50/ml RVFV strain MP-12 using cotton sticks. Blood-fed females were sorted and incubated for 21 days post infection (DPI) at 28°C. Salivation assays and dissection of wings/legs and bodies were performed on 49 females of CPM and 10 AA at 14 DPI and on 38 females of CPM and 3 AA at 21 DPI, followed by qPCR to confirm presence of RVFV RNA in the examined samples. In CPM, infection rates (virus RNA positive bodies) were 26.5 & 34.2%, dissemination rates (positive wings/legs) were 24.5, 15.8% and transmission rates (positive saliva) were 16.3 & 44.7 % at 14 and 21 DPI. In AA infection rates were 30.0 & 33.3%, dissemination rates were 10.0, 0.0% and transmission rates were 20.0 & 33.3% at 14 and 21 DPI. In conclusion, German mosquitoes (CPM-Hesse & AA-Freiburg) are competent vectors for RVFV strain MP12 for a period of 21 DPI. This indicates that Germany may be at risk for the introduction of RVFV and if it is introduced, it might threaten both human and animal health.