Susceptibility of various sand fly species to Toscana virus

Abstract

Phlebotomine sand flies transmit numerous viral pathogens, including Toscana virus (TOSV,Phenuiviridae). This arbovirus is spread in the Mediterranean area and causes a wide range of clinicalsymptoms (from non-symptomatic to serious CNS infection). While only Phlebotomus pernicious andP. perfiliewi have been confirmed as TOSV vectors, infected or TOSV-seropositive humans andanimals have been identified in regions lacking these sand fly species. Given the limitedunderstanding of TOSV and its spread, we aimed to assess the susceptibility of other sand fly speciesto TOSV, potentially expanding our knowledge of its transmission in nature. The susceptibility of P.papatasi, P. tobbi, P. sergenti, and Sergentomyia schwetzi to TOSV was tested by membrane feedingwith blood mixed with TOSV strains belonging to the genetic lineage A or B (referred to as TOSV-Aor TOSV-B). Blood-fed females were dissected at days 4, 8, and 14 post-infection for virusquantification using both infectious viral particle titration and RT-qPCR. We show that the TOSV-Adid not infect any tested sand fly species. Contrarily, TOSV-B infected P. tobbi at relatively high rates(66% and 53% at D4 and D8, respectively). Phlebotomus sergenti showed lower infection rates (5.5%)but 100% dissemination rate. Phlebotomus papatasi and S. schwetzi were 100% refractory to TOSVB.Overall, our data indicate that P. tobbi is highly susceptible to TOSV and potentially serves as theTOSV vector in the Eastern part of the Mediterranean basin, when P. sergenti is less susceptible, butits role in TOSV circulation should be also considered.