Evidence of natural Wolbachia infections in field populations of Anopheles gambiae

Abstract

Wolbachia are maternally transmitted intracellular bacteria that invade insect populations by manipulating their reproduction and immunity and thus limiting the spread of numerous human pathogens. Experimental Wolbachia infections can reduce Plasmodium numbers in Anopheles mosquitoes in the laboratory, however, natural Wolbachia infections in field anophelines have never been reported. Here we show evidence of Wolbachia infections in Anopheles gambiae in Burkina Faso, West Africa. Sequencing of the 16S rRNA gene identified Wolbachia sequences in both female and male germlines across two seasons, and determined that these sequences are vertically transmitted from mother to offspring. Whole-genome sequencing of positive samples suggests that the genetic material identified in An. gambiae belongs to a novel Wolbachia strain, related to but distinct from strains infecting other arthropods. The evidence of Wolbachia infections in natural Anopheles populations promotes further investigations on the possible use of natural Wolbachia–Anopheles associations to limit malaria transmission.

Native microbiome impedes vertical transmission of Wolbachia in Anopheles mosquitoes

“…Recently, Wolbachia sequences were detected at low frequency in field populations of A. gambiae (55). High-throughput sequencing of the 16S rRNA gene amplified from the DNA extracted from the germ lines of 30 mating couples found one male that contained Wolbachia reads (55). Although lack of statistical power precludes definitive conclusions, examination of these data identified no Asaia sequence reads in the Wolbachia-infected individual, consistent with the hypothesis that Asaia acts competitively with Wolbachia infection in Anopheles.…”

“…Using a combination of high-throughput sequencing and bacterial supplementation, we identified the bacterium Asaia as a specific agent inhibiting Wolbachia transmission in Anopheles. Recently, Wolbachia sequences were detected at low frequency in field populations of A. gambiae (55). High-throughput sequencing of the 16S rRNA gene amplified from the DNA extracted from the germ lines of 30 mating couples found one male that contained Wolbachia reads (55).…”

“…Flaminia Catteruccia and Nicola Segata for kindly providing data on Asaia 16S sequence read frequency from ref. 55. We also thank the Microscopy and Cytometry Facility at the Huck Institutes of the Life Sciences and Penn State University.…”

A comparative analysis of reproductive biology of insect vectors of human disease

“…Wolbachia infection can cause additional reproductive phenotypes, including increased fecundity and hatching rates in Aedes albopictus [57, 58]. Because of these reproductive phenotypes, Wolbachia infections can rapidly spread through natural insect populations, and have been detected in Aedes [59], Glossina [51, 60] and more recently in Anopheles species from West Africa [61]. Additionally, Wolbachia infections have also been shown to block human pathogen transmission in Ae.…”

“…aegypti [62, 63] and in An. stephensi [64, 65], prompting their current and proposed use in disease control programs [61, 66, 67] (Eliminate Dengue Program; URL: www.eliminatedengue.com). A specific effect of Wolbachia on trypanosome infection intensity or on tsetse fecundity has not yet been fully established.…”