The role of different Culex mosquito species in the transmission of West Nile virus and avian malaria parasites in Mediterranean areas

Vector-borne diseases, especially those transmitted by mosquitoes, have severe impacts on public health and economy. West Nile virus (WNV) and avian malaria parasites of the genusPlasmodiumare mosquito-borne pathogens that may produce severe disease and illness in humans and birds, respectively, and circulate in an endemic form in southern Europe. Here, we used field-collected data to identify the impact ofCulex pipiens,Cx. perexiguusandCx. modestus, on the circulation of both WNV andPlasmodiumin Andalusia (SW Spain) using mathematical modelling of the basic reproduction number (R-0). Models were calibrated with field-collected data on WNV seroprevalence andPlasmodiuminfection in wild house sparrows, presence of WNV andPlasmodiumin mosquito pools, and mosquito blood-feeding patterns. This approach allowed us to determine the contribution of each vector species to pathogen amplification. Overall, 0.7% and 29.6% of house sparrows were positive to WNV antibodies andPlasmodiuminfection, respectively. In addition, the prevalence ofPlasmodiumwas higher inCx. pipiens(2.0%), followed byCx. perexiguus(1.8%) andCx. modestus(0.7%). Three pools ofCx. perexiguuswere positive to WVN. Models identifiedCx. perexiguusas the most important species contributing to the amplification of WNV in southern Spain. ForPlasmodiummodels,R(0)values were higher whenCx. pipienswas present in the population, either alone or in combination with the other mosquito species. These results suggest that the transmission of these vector-borne pathogens depends on differentCulexspecies, and consequently, their transmission niches will present different spatial and temporal patterns. For WNV, targeted surveillance and control ofCx. perexiguuspopulations appear as the most effective measure to reduce WNV amplification. Also, preventingCulexpopulations near human settlements, or reducing the abundance of these species, are potential strategies to reduce WNV spillover into human populations in southern Spain.