Overwintering West Nile virus in active Culex pipiens mosquito populations in Greece

Abstract

The flavivirus West Nile Virus (WNV), which is transmitted by mosquitoes, poses a significant threat to both humans and animals, and its outbreaks often challenge public health in Europe and other continents. In recent years, there is an increasing trend of WNV incidence rates across several European countries. However, whether there is a year-round circulation or seasonal introduction has yet to be elucidated. Real-time polymerase chain reaction (PCR) identified WNV-positive Culex pipiens mosquitos in 6 out of 146 pools examined in winter 2022 that correspond to three out of the 24 study areas, located in two coastal regions units in Attica, Greece. Spatial dispersion of the six positive pools in the same region suggests a clustered circulation of WNV during the winter of 2022. This is the first study that documents the identification of WNV in Cx. pipiens populations, captured in adult traps during winter period. Our findings underscore the need to extend entomological surveillance programs to include the winter period, specifically in temperate climates and historically affected areas by WNV.

Keywords: Culex pipiens; Biotypes; Host searching; Overwintering; West Nile virus.

Fig. 1

Dispersion of sampling sites (yellow marks) for West Nile virus (WNV) detection in the Attica Region. The red and black dots indicate the positions of the positive samples recorded during winter 2022 and winter 2023, respectively and the frequency of detection