Diverse novel resident Wolbachia strains in Culicine mosquitoes from Madagascar

Abstract

Wolbachia endosymbiotic bacteria are widespread throughout insect species and Wolbachia transinfected in Aedes mosquito species has formed the basis for biocontrol programs as Wolbachia strains inhibit arboviral replication and can spread through populations. Resident strains in wild Culicine mosquito populations (the vectors of most arboviruses) requires further investigation given resident strains can also affect arboviral transmission. As Madagascar has a large diversity of both Culicine species and has had recent arboviral outbreaks, an entomology survey was undertaken, in five ecologically diverse sites, to determine the Wolbachia prevalence. We detected diverse novel resident Wolbachia strains within the Aedeomyia, Culex, Ficalbia, Mansonia and Uranotaenia genera. Wolbachia prevalence rates and strain characterisation through Sanger sequencing with multilocus sequence typing (MLST) and phylogenetic analysis revealed significant diversity and we detected co-infections with the environmentally acquired bacteria Asaia. Mosquitoes were screened for major arboviruses to investigate if any evidence could be provided for their potential role in transmission and we report the presence of Rift Valley fever virus in three Culex species: Culex tritaeniorhynchus, Culex antennatus and Culex decens. The implications of the presence of resident Wolbachia strains are discussed and how the discovery of novel strains can be utilized for applications in the development of biocontrol strategies.

Systematic Review of Wolbachia Symbiont Detection in Mosquitoes: An Entangled Topic about Methodological Power and True Symbiosis

“…Given that these strategies to control mosquito populations or pathogen transmission rely on curated information about the Wolbachia status of mosquito species and natural populations, prior knowledge and continued monitoring of the presence of Wolbachia in mosquitoes is crucial to plan and implement such control programs. Wolbachia can be detected through various molecular techniques that show variable sensitivity and specificity, such as polymerase chain reaction (PCR) (with specific and/or degenerate primers), PCR with various markers such as multilocus sequencing Typing (MLST), quantitative PCR (qPCR), microscopy methods, such as Fluorescent In Situ Hybridization (FISH), electron microscopy, and others [42][43][44][45]. The popularization of molecular methods has broadened the capacity of many laboratories to perform Wolbachia DNA detection in several insect species while the different microscopy techniques have been used by a small number of researchers [46].…”

Detection of diverse Wolbachia 16S rRNA sequences at low titers from malaria vectors in Kayin state, Myanmar

“…Natural Wolbachia infections may have important effects on mosquito populations and dynamics of diseases transmission but they are less well described 9 . Wolbachia DNA was detected by PCR in 27 mosquito genera including the medically important Aedes , Armigeres , Culex , Mansonia and Stegomiya 9– 18 . Interestingly, this organism was not detected in malaria mosquitoes until recent observations of naturally infected anopheline vectors in Africa 9, 13, 19– 24 .…”

“…The paragraph describing natural Wolbachia infections in mosquitoes also needs further references 1 , 2 , 3 .…”

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

“…This study and previous studies measuring a direct impact on Plasmodium infection in wild populations are dependent on parasite infection rates which can be low even in malaria-endemic areas [26] and particularly for the infective sporozoite stage [66]. Low pathogen prevalence rates are also limiting factors in assessing the effect of natural strains of Wolbachia on arboviruses in wild mosquito populations [67]. In addition to looking at effects on Plasmodium prevalence in field populations, further work should look to undertake vector competence experiments with colonised populations and to determine if these Wolbachia strains are present in tissues such as the midgut and salivary glands which are critical to sporogony.…”