Lack of robust evidence for a Wolbachia infection in Anopheles gambiae from Burkina Faso

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Résumé

he endosymbiont Wolbachia can have major effects on the reproductive fitness, and
vectorial capacity of host insects and may provide new avenues to control mosquitoborne pathogens. Anopheles gambiae s.l is the major vector of malaria in Africa but the
use of Wolbachia in this species has been limited by challenges in establishing stable
transinfected lines and uncertainty around native infections. High frequencies of infection of Wolbachia have been previously reported in An. gambiae collected from the Valle
du Kou region of Burkina Faso in 2011 and 2014. Here, we re-evaluated the occurrence
of Wolbachia in natural samples, collected from Valle du Kou over a 12-year time span,
and in addition, expanded sampling to other sites in Burkina Faso. Our results showed
that, in contrast to earlier reports, Wolbachia is present at an extremely low prevalence
in natural population of An. gambiae. From 5341 samples analysed, only 29 were positive
for Wolbachia by nested PCR representing 0.54% of prevalence. No positive samples
were found with regular PCR. Phylogenetic analysis of 16S rRNA gene amplicons clustered across supergroup B, with some having similarity to sequences previously found in
Anopheles from Burkina Faso. However, we cannot discount the possibility that the
amplicon positive samples we detected were due to environmental contamination or
were false positives. Regardless, the lack of a prominent native infection in An. gambiae
s.l. is encouraging for applications utilizing Wolbachia transinfected mosquitoes for
malaria control

Mots-clés

Anopheles gambiae, biocontrol, native infection, population replacement, population suppression, wAnga, Wolbachia