Wide detection of Aedes flavivirus in north-eastern Italy: a European hot-spot of emerging mosquito-borne diseases

The pattern of flavivirus infection in mosquitoes belonging to the genera Aedes and Culex collected in two regions of north-eastern Italy (Trentino and Veneto) was assessed. Mosquitoes were collected during 2012 and screened for flaviviruses using a generic reverse transcription-nested-PCR targeted on a region of the non-structural NS5 gene. The phylogenetic analysis was performed on a fragment of ~1000 bp. Virus isolation was attempted in C6/36 insect cell lines and the infected cell cultures were studied by electron microscopy. We detected a wide distribution of Aedes flavivirus (AeFV) in Aedes albopictus, with higher infection prevalence in Trentino than in Veneto. In Culex pipiens collected in Veneto, we detected a new sequence of an insect-specific flavivirus and one of Usutu virus. Interestingly, we detected AeFV in C. pipiens, for the first time to our knowledge, in both regions. Viral isolation in cell culture was successful for AeFV. AeFV sequences found in Veneto showed a high percentage of similarity to those detected in Trentino and to those previously reported in other areas of northern Italy. Co-infections with different flaviviruses were not detected.