New enemies: contribution of Culex perexiguus in the transmission dynamic of West Nile virus.

Vector-borne pathogens like West Nile virus (WNV), an emerging zoonotic arbovirus, are strongly influenced by mosquito community dynamics. WNV is maintained between birds and mosquitoes, with humans and other mammal species (such as equids) as dead-end hosts. In Spain, the role of Culex perexiguus as main vector of WNV is gaining significance over Cx. pipiens due to differences in feeding behavior, and vector competence, and ecological preferences that affect WNV transmission. Using a SEIR (Susceptible-Exposed-Infectious-Recovered) model, we examined how mosquito abundance and feeding preferences impact WNV spread in a Mediterranean region. Our results suggest that, under the conditions simulated, Cx. pipiens alone is unlikely to sustain WNV transmission in the study area, whereas Cx. perexiguus may contribute more substantially to outbreak dynamics. Increased avian-feeding preferences were associated with higher outbreak intensity, although the basic reproduction number (R₀) remained below one in all scenarios. Sensitivity analyses highlighted that bite rates and abundance of Cx. perexiguus are key drivers of WNV spread in our model. Furthermore, a dilution effect was observed when Cx. pipiens fed more frequently on dead-end hosts, which contributed to lowering R₀. Our findings underscore the need for species-specific vector surveillance to inform public health interventions and control strategies for WNV and other mosquito-borne diseases.