Divergent host preferences of above‐ and below‐ground Culex pipiens mosquitoes and their hybrid offspring

Abstract

Culex pipiens form pipiens and Cx. pipiens form molestus (Diptera: Culicidae) belong to a cosmopolitan taxonomic group known as the Pipiens Assemblage. Hybridization between these forms is thought to contribute to human transmission of West Nile virus (WNV) in North America. Complementary choice and no-choice landing assays were developed to examine host acceptance by North American Cx. pipiens in the laboratory. Populations collected from above- and below-ground sites in suburban Chicago were identified as forms pipiens and molestus using a polymerase chain reaction-based assay. Avian and human host acceptance was then quantified for the two populations, as well as for their hybrid and backcross offspring. No-choice tests were used to demonstrate that both the pipiens and molestus forms were capable of feeding on human and avian hosts. Choice tests were used to demonstrate that form pipiens females were strongly avian-seeking; an individual's probability of accepting the chick host was 85%. Form molestus females were more likely to accept the human host (87%). Rates of host acceptance by F1 and backcross progeny were intermediate to those of their parents. The results suggest that host preferences in Cx. pipiens are genetically determined, and that ongoing hybridization between above- and below-ground populations is an important contributor to epizootic transmission of WNV in North America.

An overview of mosquitoes and emerging arboviral infections in the Zagreb area, Croatia

“…A recently published study suggested that hybrid offsprings between the pipiens and molestus forms are an important for epizootic transmission of WNV in North America [66]. During the 2012 outbreak in Croatia, mosquitoes were sampled within the area of appearance of WNV neuroinvasive human cases in three north-eastern counties.…”

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

“…These laboratory findings are supported by field studies carried out in northern Europe, which reported serological evidence of WNV in sentinel chickens, resident birds, and migratory birds in the United Kingdom (Buckley et al 2006, Buckley et al 2003, and in migratory birds in Germany (Linke et al 2007). This evidence may suggest that WNV is already circulating among birds Introduction 1 they have a relatively high infection prevalence in the field (Engler et al 2013, Hayes et al 2005, strong preference to feed on bird hosts (Fritz et al 2015, Hamer et al 2009, Osório et al 2014, and high abundance during summer (Chaskopoulou et al 2016, Spielman 2001, which together makes Cx. pipiens a potentially important contributor to WNV transmission (Kilpatrick et al 2005).…”

“…The two biotypes can hybridize, and hybrids show intermediate behaviour. Due to their more opportunistic feeding behaviour, hybrids are considered important bridge vectors which can transmit WNV from birds to humans (Fritz et al 2015, Kilpatrick et al 2005. Behavioural differences between biotypes may have implications for their contribution to the WNV transmission cycle.…”

“…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. Furthermore, biotype pipiens and biotype molestus can form hybrids which show intermediate host preference (Fritz et al 2015). As a result of this, hybrids can play an important role in bridging WNV from birds to humans ).…”

“…As a consequence, biotype pipiens plays an important role in the natural transmission cycle of WNV. Hybrids between the two biotypes have an intermediate host preference, which makes them ideal vectors to bridge WNV from birds to mammals (Fritz et al 2015). The presence and abundance of hybrids may, therefore, strongly increase the risk of WNV outbreaks in the human population.…”