Are the Culex pipiens biotypes pipiens, molestus and their hybrids competent vectors of avian Plasmodium?

The common house mosquito Culex pipiens s.l., widely distributed in Europe, Africa, and North America has two recognized biotypes, Cx. pipiens biotype pipiens and Cx. pipiens biotype molestus, which hybridize. Despite their morphological similarities, these biotypes may exhibit ecological differences. This complex ecological mosaic may affect the interaction of Cx. pipiens with pathogens like avian Plasmodium, which is transmitted to wildlife. Although the vector competence for Cx. pipiens biotype molestus has been well studied, there is a lack of studies comparing the vector competence of Cx. pipiens biotype pipiens and their hybrids for the transmission of avian Plasmodium. Here, we evaluated the vector competence of the Cx. pipiens biotypes pipiens, molestus and their hybrids for the transmission of two avian Plasmodium species. Mosquitoes were allowed to feed on blood of wild infected birds and the presence of DNA of Plasmodium in head-thorax and saliva of mosquitoes was molecularly evaluated at 13 day-post exposure. The transmission rates (i.e., the detection of parasite DNA in mosquito saliva) for Plasmodium cathemerium were similar for the two biotypes of Cx. pipiens and their hybrids while Plasmodium relictum DNA was only found in the saliva of Cx. pipiens biotype pipiens. In addition, P. cathemerium was significantly more prevalent than P. relictum in the saliva of Cx. pipiens biotype pipiens. Our results suggest that avian Plasmodium is transmitted by both Cx. pipiens biotypes and their hybrids although differences could be found depending of the parasite species studied. Differences in the abundance of each biotype and their hybrids within areas characterized by distinct environmental conditions, along with variations in their blood-feeding patterns and the parasites infecting birds, could ultimately determine differences in the relevance of each Cx. pipiens biotype in the transmission of avian Plasmodium.