Comparative morphological and molecular analysis confirms the presence of the West Nile virus mosquito vector, Culex univittatus, in the Iberian Peninsula

Abstract

Background: Culex univittatus and Culex perexiguus mosquitoes (Diptera: Culicidae) are competent arbovirus vectors, but with unclear morphological differentiation. In Europe, and in the Iberian Peninsula in particular, the presence of either or both species is controversial. However, in order to conduct adequate surveillance for arboviruses in this region, it is crucial to clarify whether Cx. univittatus is present or not, as well as to critically assess existing differentiation tools. This study aimed to clarify this situation, by morphological and molecular phylogenetic comparison of Iberian specimens deemed as Cx. univittatus, with others of South African origin, i.e. from the type-locality region. Methods: Thus, morphological characteristics useful to distinguish both species, such as midfemur pale line, hindfemur R ratio, seta g R1 ratio, seta f shape, length of ventral arm of phalosome and number of setae on IX tergal abdominal segment, were observed. A phylogenetic analysis based on cox1 mtDNA, of which there were no sequences from Cx. univittatus yet available in the GenBank database, was performed. Results: This analysis showed that Iberian and South African specimens are morphologically similar, except for the length of the ventral arm of the phalosome, which was higher in the Iberian specimens. Although the Iberian specimens could not be accurately identified using BOLD Systems, phylogenetic analysis still grouped these closer to South African Cx. univittatus, than to Cx. perexiguus from Turkey and Pakistan, despite the observed segregation of both taxa as two individual monophyletic clusters with shared common ancestry. Conclusions: This survey demonstrates that the West Nile virus vector Cx. univittatus is present in the Iberian Peninsula.