Microbial Pre-exposure and Vectorial Competence of Anopheles Mosquitoes.

Constentin Dieme,Brice Rotureau,Christian Mitri

doi:10.3389/fcimb.2017.00508

Abstract

Anopheles female mosquitoes can transmit Plasmodium, the malaria parasite. During their aquatic life, wild Anopheles mosquito larvae are exposed to a huge diversity of microbes present in their breeding sites. Later, adult females often take successive blood meals that might also carry different micro-organisms, including parasites, bacteria, and viruses. Therefore, prior to Plasmodium ingestion, the mosquito biology could be modulated at different life stages by a suite of microbes present in larval breeding sites, as well as in the adult environment. In this article, we highlight several naturally relevant scenarios of Anopheles microbial pre-exposure that we assume might impact mosquito vectorial competence for the malaria parasite: (i) larval microbial exposures; (ii) protist co-infections; (iii) virus co-infections; and (iv) pathogenic bacteria co-infections. In addition, significant behavioral changes in African Anopheles vectors have been associated with increasing insecticide resistance. We discuss how these ethological modifications may also increase the repertoire of microbes to which mosquitoes could be exposed, and that might also influence their vectorial competence. Studying Plasmodium–Anopheles interactions in natural microbial environments would efficiently contribute to refining the transmission risks.

Highlights

Vector-borne diseases are a major cause of human mortality and morbidity in the World, among which malaria is a prominent threat
While the human immunodeficiency virus (HIV) virus is not transmitted by mosquitoes, it is noteworthy that it has a short lifespan in their digestive tract (48 h) (Bockarie and Paru, 1996; Iqbal, 1999). During this time frame (48 h), proteins from the virion surface could induce an immune response in Anopheles mosquitoes biting on a co-infected human host, which may further impact on the development of Plasmodium
Another study showed that the Wolbachia wPip(Sl) strain increases the susceptibility of C. pipiens mosquitoes to the avian parasite Plasmodium relictum (Zélé et al, 2014a), suggesting that Wolbachia-infected mosquitoes may have an opposite effect to that observed on the vectorial competence of Aedes and Anopheles for dengue and P. falciparum, respectively

Summary

Introduction

Vector-borne diseases are a major cause of human mortality and morbidity in the World, among which malaria is a prominent threat. We first propose several relevant scenarios highlighting microbial exposure of Anopheles mosquito vectors that might impact their vectorial competence for Plasmodium. With the recent development of generation sequencing (NGS) technologies, such studies will become more affordable for identifying new bacteria (Gimonneau et al, 2014), viruses, as well as protists (Belda et al, 2017) communities that might shape the immune system of the mosquito larvae and probably the vectorial competence of the emerging Anopheles adults (Figures 1A,B).

Results

Conclusion