Evidence for natural hybridisation and novel Wolbachia strain superinfections in the Anopheles gambiae complex from Guinea

1. Summary Wolbachia , a widespread bacterium which can influence mosquito-borne pathogen transmission, has recently been detected within Anopheles (An.) species that are malaria vectors in Sub-Saharan Africa. Although studies have reported Wolbachia strains in the An. gambiae complex, apparent low density and prevalence rates require confirmation. In this study, wild Anopheles mosquitoes collected from two regions of Guinea were investigated. In contrast to previous studies, RNA was extracted from adult females (n=516) to increase the chances for detection of actively expressed Wolbachia genes, determine Wolbachia prevalence rates and estimate relative strain densities. Molecular confirmation of mosquito species and Wolbachia Multilocus sequence typing (MLST) were carried out to analyse phylogenetic relationships of mosquito hosts and newly discovered Wolbachia strains. Strains were detected in An. gambiae s.s. (prevalence rates of 0.0-2.8%) from the Faranah region, An. melas (prevalence rate of 11.6% - 16/138) and hybrids between these two species (prevalence rate of 40.0% - 6/15) from Senguelen in the Maferinyah region. Furthermore, a novel high-density strain, termed w AnsX, was found in an unclassified Anopheles species. The discovery of novel Wolbachia strains (particularly in members, and hybrids, of the An. gambiae complex) provides further candidate strains that could be used for future Wolbachia -based malaria biocontrol strategies.