Aedes invasive mosquitoes (AIMs) play a key role as vectors of several pathogens of public health relevance. Four species have been established in Europe, including Aedes aegypti, Aedesalbopictus, Aedes japonicus and Aedes koreicus. In addition, Aedes atropalpus has been repeatedly recorded although it has not yet been established. In spite of their importance in the transmission of endemic (e.g., heartworms) and imported pathogens (e.g., dengue virus), basic information of parameters affecting their vectorial capacity is poorly investigated. The aim of this study is to review the blood feeding patterns of these invasive mosquito species in Europe, summarizing available information from their native and introduced distribution ranges. The feeding patterns of mosquitoes constitute a key parameter affecting the contact rates between infected and susceptible hosts, thus playing a central role in the epidemiology of mosquito-borne pathogens. Our results highlight that these mosquito species feed on the blood of different vertebrate groups from ectotherms to birds and mammals. However, humans represent the most important source of blood for these species, accounting for 36% and 93% of hosts identified for Ae. japonicus and Ae. aegypti, respectively. In spite of that, limited information has been obtained for some particular species, such as Ae. koreicus, or it is restricted to a few particular areas. Given the high vector competence of the four AIM species for the transmission of different emerging arboviruses such as dengue, Chikungunya, Zika or Yellow fever viruses and their high feeding rates on humans, these AIM species may have an important impact on the vectorial capacity for such pathogens on urban and periurban areas. Finally, we propose directions for future research lines based on identified knowledge gaps.

West Nile Virus (WNV) is a mosquito vector-borne zoonosis with an increasing incidence in Europe that has become a public health concern. In Spain, although local circulation has been known for decades, until 2020, when a large outbreak occurred, West Nile Virus cases were scarce and mostly occurred in southern Spain. Since then, there have been new cases every year and the pathogen has spread to new regions. Thus, monitoring of circulating variants and lineages plays a fundamental role in understanding WNV evolution, spread and dynamics. In this study, we sequenced WNV consensus genomes from mosquito pools captured in 2022 as part of a newly implemented surveillance program in southern Spain and compared it to other European, African and Spanish sequences. Characterization of WNV genomes in mosquitoes captured in 2022 reveals the co-circulation of two WNV lineage 1 variants, the one that caused the outbreak in 2020 and another variant that is closely related to variants reported in Spain in 2012, France in 2015, Italy in 2021–2022 and Senegal in 2012–2018. The geographic distribution of these variants indicates that WNV L1 dynamics in southern Europe include an alternating dominance of variants in some territories.

Studying host specificity is crucial to understanding the ability of parasites to spread to new hosts and trigger disease emergence events. The relationship between host specificity, and parasite prevalence and infection intensity, has typically been studied in the context of two opposing hypotheses. According to the trade-off hypothesis generalist parasites, which can infect a broad range of hosts, will reach a lower prevalence and infection intensity than more specialist parasites due to the higher costs to adapt to multiple host immune systems. In contrast, the niche breadth hypothesis proposes that generalists' ability to infect more host species makes them more efficient in colonising host communities and thus they are found at higher prevalences and infection intensities. This study aims to test these hypotheses using the widespread avian malaria parasites of the genera Plasmodium and the related malaria-like parasite Haemoproteus. Overall, 1188 wild house sparrows from 17 localities in southwestern Spain were screened for parasite presence and intensity of infection. For each lineage found infecting house sparrows, we estimated host specificity as i) the number of different bird taxa infected by that lineage according to the MalAvi database and ii) an index that accounts for the phylogenetic relatedness between the host species. Parasite infections were recorded in 419 house sparrows, and nine Plasmodium and three Haemoproteus lineages were identified. Prevalence was positively associated with the number of host species. Lineages found in more localities showed both higher prevalence and host range. Overall, these results support the niche breadth hypothesis in relation to blood parasites infecting house sparrows.

The reference genomes of Culex laticinctus, Culex modestus, Culex perexiguus, and Culex theileri offer crucial resources for exploring the genetic basis of vector competence for different pathogens, including the emerging West Nile virus. Each genome was assembled into three contiguous chromosomal pseudomolecules. These chromosome-level assemblies encompass 834, 698, 436, and 934 Mb, respectively. They are composed of 3,284, 4,220, 1,917, and 2,704 contigs and 312, 979, 475, and 709 scaffolds, with contig N50 values of 434, 313, 473, and 770 kb, and scaffold N50 values of 292, 246, 150, and 281 Mb, respectively. These genomes offer an essential genomic resource for advancing our understanding of Culex evolution and population genomic analyses, which will help to implement sustainable mosquito control efforts and disease prevention.

Culex pipiens is a major vector of West Nile Virus (WNV) in Europe and has a complex evolutionary history that has been linked to the probability of WNV spillover to humans. Here, we present a population genomic analysis of Cx. pipiens from a WNV hotspot in southwestern Spain. Whole-genome sequencing of 217 individuals from 24 localities revealed that population structure is mainly shaped by the coexistence of pipiens and molestus ecotypes. Despite clustering, genome-wide divergence between ecotypes was low, consistent with shared ancestral variation. Furthermore, Wolbachia infection was heterogeneous across the study area, where some Culex pipiens pipiens remain uninfected. We also identified three new polymorphic chromosomal inversions on chromosomes 1 and 3 that segregate independently. Although inversions did not underlie ecotypic differentiation, they were enriched for genes involved in olfaction and insecticide resistance pathways, suggesting potential adaptive and epidemiological relevance. Distance-based redundancy analyses showed that ecotype identity explained the largest fraction of genetic variance, with additional contributions from Wolbachia infection, habitat type (urban versus rural) and geographic distance. These results reveal that partial ecotypic differentiation, symbiont infection, and habitat interact to shape population structure in Cx. pipiens , with implications for vector ecology and disease transmission.