A Microsporidian blocksPlasmodium falciparumtransmission inAnopheles arabiensismosquitoes

Abstract

Malaria imposes an enormous burden on sub-Saharan Africa, and evidence that incidence could be starting to increase again1suggests the limits of currently applied control strategies have now been reached. A possible novel control approach involves the dissemination in mosquitoes of inherited symbiotic microbes to block transmission. This strategy is exemplified by the use of transmission-blockingWolbachiainAedes aegyptiagainst dengue virus2–7. However, in theAnopheles gambiaecomplex, the primary African vectors of malaria, there limited reports of inherited symbionts with transmission-blocking capacity8–10. Here we show that a newly discovered vertically transmitted species ofMicrosporidiasymbiont in theAn. gambiaecomplex blocksPlasmodiumtransmission.Microsporidia MBis present at moderate prevalence in geographically dispersed populations ofAn. arabienesisin Kenya, localized to the mosquito midgut and ovaries, and is not associated with significant reductions in adult host fecundity or survival. Field collectedMicrosporidia MB-infectedAn. arabiensiswere never found to harborP. falciparumgametocytes and on experimental infection withP. falciparumno sporozoites could be detected inMicrosporidia MB-infected mosquitos. As aPlasmodiumtransmission-blocking microbe that is non-virulent and vertically transmitted,Microsporidia MBcould be exploited as a novel malaria control tool.