Latitudinal Diversity of Culex pipiens Biotypes and Hybrids in Farm, Peri-Urban, and Wetland Habitats in Europe

Abstract

Despite the presence of Culex (Cx.) pipiens mosquitoes and circulation of West Nile virus (WNV), WNV outbreaks have so far not occurred in northern Europe. The species Cx. pipiens consists of two morphologically identical biotypes, pipiens and molestus, which can form hybrids. Until now, population dynamic studies of Cx. pipiens have not differentiated between biotypes and hybrids at the European scale, nor have they used comparative surveillance approaches. We therefore aimed to elucidate the relative abundance of Cx. pipiens biotypes and hybrids in three habitat types at different latitudes across Europe, using two different surveillance traps. BG-Sentinel and Mosquito-Magnet Liberty Plus traps were placed in three habitat types (farms, peri-urban, wetlands), in three European countries (Sweden, The Netherlands, Italy). Collected Cx. pipiens mosquitoes were identified to biotype with real-time PCR. Both trap types collected equal ratios of the biotypes and their hybrids. From northern to southern latitudes there was a significant decrease of pipiens and an increase of molestus. Habitat types influenced the relative ratios of biotypes and hybrids, but results were not consistent across latitudes. Our results emphasize the need to differentiate Cx. pipiens to the biotype level, especially for proper future WNV risk assessments for Europe.

Human biting Culex pipiens bioform molestus is spread in several areas in south Sweden

“…pipiens f molestus while none of the specimens collected in traps were bioform molestus. Contrasting with the results from (Vogels, Möhlmann et al 2016) where they found the Cx. pipiens f molestus in rural sites and hybrids in an urban site where no nuisance problems have been reported.…”

“…In northern Europe, Cx. pipiens bioforms have been thought to be more isolated from each other and hybrids are less common , Vogels, van de Peppel et al 2015, Vogels, Möhlmann et al 2016. Compared to the few previous reports of Culex pipiens f molestus in Sweden we have found specimens in several rural areas where we would not have expected it to be present.…”

“…There are also findings of three Cx. pipiens f molestus from a farm and two wetlands outside Linköping in central south Sweden and hybrids in Linköping (Vogels, Möhlmann et al 2016). However, there are no other studies that suggest that Cx.…”

Modelling West Nile virus transmission risk in Europe: effect of temperature and mosquito biotypes on the basic reproduction number

“…The biotype composition of the mosquito population, which has been shown to be highly variable across different locations in Europe 31, 32 . To express the variability we selected three representative biotype compositions; either dominated by pipiens ( m p  = 0.8, m m  = 0.1, and m h  = 0.1), dominated by molestus ( m p  = 0.1, m m  = 0.8, and m h =  0.1) or equal ratios of the three biotypes ( m p  = 0.33, m m  = 0.33, and m h  = 0.33).…”

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

“…Several studies have now focused on biotype composition in different countries in Europe (Di Luca et al 2016, Gomes et al 2013a, Gomes et al 2009, Osório et al 2014, Rudolf et al 2013, Vogels et al 2016b, Zittra et al 2016. Thus far, most of these studies (including chapters 2 and 3) presented the average population composition, by combining data from mosquito collections of varying periods of time.…”