Feeding patterns of molestus and pipiens forms of Culex pipiens (Diptera: Culicidae) in a region of high hybridization

Abstract

BackgroundTwo biological forms of the mosquito Culex pipiens s.s., denoted pipiens and molestus, display behavioural differences that may affect their role as vectors of arboviruses. In this study, the feeding patterns of molestus and pipiens forms were investigated in Comporta (Portugal), where high levels of inter-form admixture have been recorded.MethodsIndoor and outdoor mosquito collections were performed in the summer of 2010. Collected Cx. pipiens s.l. females were molecularly identified to species and form by PCR and genotyped for six microsatellites. The source of the blood meal in post-fed females was determined by ELISA and mitochondrial DNA sequencing.ResultsThe distribution of the forms differed according to the collection method. The molestus form was present only in indoor collections, whereas pipiens and admixed individuals were sampled both indoors and outdoors. In both forms, over 90% of blood meals were made on avian hosts. These included blood meals taken from Passeriformes (Passer domesticus and Turdus merula) by females caught resting inside domestic shelters.ConclusionGenetic structure and blood meal analyses suggest the presence of a bird biting molestus population in the study area. Both forms were found to rest indoors, mainly in avian shelters, but at least a proportion of females of the pipiens form may bite outdoors in sylvan habitats and then search for anthropogenic resting sites to complete their gonotrophic cycle. This behaviour may potentiate the accidental transmission of arboviruses to humans in the region.

Culex pipiens as a potential vector for transmission of Dirofilaria immitis and other unclassified Filarioidea in Southwest Spain

“…The detection of filarioid worms with a possible avian origin in Cx. pipiens, mainly of the pipiens form and hybrids is consistent with its ornithophilic habits ( Gomes et al, 2013), considering also that it feeds mainly (83%) on a high diversity of avian species (Hamer et al, 2009), as well as with the abundance of migratory birds in this area, mainly from Africa (WysInfo Docuwebs, 2015).…”

“…Moreover, the analysis of ITS-2 sequences also indicated the presence of haplotype H2 as well as hybrid forms in mosquitoes with filarioid DNA. Despite its usefulness, genetic analysis of mosquito populations solely based on such a strategy is not devoid of analytical limitations, which could be overcome via combination with microsatellite analyses in future studies ( Gomes et al, 2013).…”

The role of Culex pipiens mosquitoes in transmission of West Nile virus in Europe

“…Biotype molestus and hybrids contribute remarkably less to WNV establishment, especially in areas with low bird occurrence, because they will readily feed on the more abundant mammalian hosts. However, a shift in feeding behaviour has been observed for biotype molestus in areas with high bird abundance (Gomes et al 2013b). Such shifting feeding behaviour would increase the contribution of both biotype molestus and hybrids to WNV transmission.…”

“…Biotype molestus prefers mammals, including humans, as hosts, and remains active year-round (Marshall & Staley 1935, Shute 1941, Willcox 1941. Host availability can induce a strong shift in host feeding behaviour of biotype molestus from mammals to birds, especially in areas with high bird densities (Gomes et al 2013b). Previously, biotype molestus has been described as occurring underground , but recent studies show that both biotypes occur sympatrically in aboveground habitats throughout Europe (Di Luca et al 2016, Osório et al 2014, Rudolf et al 2013.…”

“…Host availability also plays an important role in the selection for hosts. Approximately 90 % of females of the mammophilic molestus biotype that were collected from inside chicken coops in Portugal, had blood-fed on birds (Gomes et al 2013b). Hybrids between the pipiens and molestus biotypes are hypothesized to have intermediate behavioural traits and this may favour the transmission of WNV from birds to humans , Kilpatrick et al 2005.…”