Summary
A 30-month study of wild mosquitoes in western Kenya found that Microsporidia MB infection was associated with lower odds of Plasmodium falciparum infection. The association was stronger in mosquitoes with high-intensity symbiont infections.
A 30-month field study in western Kenya found that wild Anopheles arabiensis mosquitoes carrying the symbiont Microsporidia MB had lower odds of infection with Plasmodium falciparum, the parasite that causes malaria. The bioRxiv preprint reports an association of about 50% lower odds overall, with a stronger association in mosquitoes with high-intensity symbiont infections.
The finding adds evidence from wild mosquito populations to earlier laboratory work on Microsporidia MB as a possible way to impede parasite development. It does not measure malaria infections in people: the reported outcome is P. falciparum infection in mosquitoes.
What the field study found
The researchers monitored Microsporidia MB in wild An. arabiensis over 30 months. They identified distinct low- and high-intensity infection patterns, which the authors say are consistent with horizontal transmission between mosquitoes and vertical transmission from parent to offspring, respectively.
Mosquitoes carrying the symbiont had approximately 50% lower odds of P. falciparum infection overall. The reported association varied with symbiont intensity: high-intensity infections were associated with approximately 60% lower odds, compared with approximately 34% for low-intensity infections.
These are reductions in odds, not percentage-point changes in the share of mosquitoes infected. The results suggest that how much Microsporidia MB is present may be relevant to its parasite-blocking effect in natural populations.
Relevance to malaria control
Microsporidia MB is a naturally occurring microorganism associated with An. arabiensis. The study’s field observations support investigating it as a candidate for malaria control, and the intensity pattern gives researchers a factor to consider when assessing how effectively it might limit parasite development.
The evidence is observational field research in mosquitoes, rather than a test of deliberately introducing the symbiont or a measurement of human malaria cases. The paper is a preprint, so its findings are reported before peer review.