Overwintering in abandoned animal burrows as a reservoir for arboviruses in Central Europe.

s.s./ belong to the most widespread mosquito taxa in Europe and are the main vectors of Sindbis, West Nile and Usutu virus. The adult overwintering females can act as reservoir for these arthropod-borne viruses (arboviruses), thus contributing to their local persistence when transmission cycles are interrupted during the winter. However, the main overwintering sites of are unknown. In a study from 2017, 3455 s.s./ specimens were collected from abandoned animal burrows in Poznan, Poland. These specimens were retrospectively identified to species-level with a PCR assay, which revealed as dominant species (> 60%). Motivated by these results, we conducted a field study from February to July 2022 to systematically analyse the overwintering site patterns of s.s./. Mosquitoes were sampled using pipe traps in abandoned animal burrows ( = 20) and with aspirators in nearby anthropogenic overwintering sites ( = 23). All s.s./ were screened for RNA. In total, 4710 mosquitoes of five different taxa were collected from anthropogenic sites. 3977 of them were identified as / (: 85%, : 1%, pools with both species: 14%). In contrast, only / (1688 specimens) were collected from animal burrows dominated by (52%), followed by pools with both species (40%) and (8%). A single pool of 10 specimens collected from an animal burrow was positive for Usutu virus. The detection of Usutu virus demonstrates that can act as winter reservoir for arboviruses. Abandoned animal burrows may by the primary overwintering site for the species and should be considered in future surveillance programmes, when sampling overwintering mosquitoes.