Microsporidia: a promising vector control tool for residual malaria transmission

Long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS) haveresulted in a major decrease in malaria transmission. However, it has becomeapparent that malaria can be effectively transmitted despite high coverage ofLLINs/IRS. Residual transmission can occur due toPlasmodium-carryingAnophelesmosquitoes that are insecticide resistant and have feeding andresting behavior that reduces their chance of encountering the currentlydeployed indoor malaria control tools. Residual malaria transmission is likelyto be the most significant hurdle to achieving the goal of malaria eradicationand research and development towards new tools and strategies that cancontrol residual malaria transmission is therefore critical. One of the mostpromising strategies involves biological agents that are part of the mosquitomicrobiome and influence the ability ofAnophelesto transmitPlasmodium.These differ from biological agents previously used for vector control in thattheir primary effect is on vectoral capacity rather than the longevity andfitnessofAnopheles(which may or may not be affected). An example of this type ofbiological agent isMicrosporidia MB, which was identified infield collectedAnopheles arabiensisand caused complete inhibition ofPlasmodiumfalciparumtransmission without effecting the longevity andfitness of thehost.Microsporidia MBbelongs to a unique group of rapidly adapting andevolving intracellular parasites and symbionts called microsporidia. In thisreview we discuss the general biology of microsporidians and the inherentcharacteristics that make some of them particularly suitable for malaria control.We then discuss the research priorities for developing a transmission blockingstrategy for the currently leading microsporidian candidateMicrosporidia MBfor malaria control