A newly identified microbe, named Microsporidia MB, can prevent mosquitoes from being infected by malaria parasites. This microbe could be used to block the transmission of malaria parasites from mosquito vectors to humans, according to new research published by researchers from the International Centre of Insect Physiology and Ecology (icipe) in Kenya and the University of Glasgow in the United Kingdom. 

This breakthrough comes at a time when the World Health Organisation (WHO) has warned that the current COVID-19 outbreak could increase deaths from malaria as focus shifts towards the coronavirus, and called for continued research and advancements in this area. 

“Healthy insects often have microbial symbionts inside their bodies and cells, which can have major effects on the biology of their hosts,” explained Jeremy Herren, lead researcher on the study, in a press release. “At icipe, my team’s research is focused on this type of microbial symbiont, especially when they may be interfering with transmission of diseases by insects.”

Scientists reported that mosquitos carrying the microbial symbiont Microsporidia MB could not be infected with Plasmodium falciparum, the most common malaria parasite in Africa, after experimental infection with the microbe in laboratories. The results hold in nature as well – low levels of the microbe naturally occur in mosquitoes in Kenya, preventing some mosquitos from carrying the malaria parasite.

Since Plasmodium falciparum must be transmitted between mosquitoes and humans to fulfill its full life cycle, protecting mosquitoes from infection by the parasite could break the chain of transmission. So far, most malaria interventions have only focused on preventing humans from being infected.

The research, which has been published in Nature Communications, details the findings of studies conducted along the shores of Lake Victoria in Kenya, a natural habitat of the Anopheles mosquitoes that serve as malaria vectors. Africa, where malaria kills over 400,000 people a year, contributed to more than 90% of the global deaths from the disease in 2017 alone. While use of cost-effective interventions like insecticide-treated nets have reduced malaria cases by 40% in 2015, progress has since stagnated partly due to increased resistance to insecticide and antimalarial medications. New tools are desperately needed in order to continue making gains against the disease.

The study also found that Microsporidia MB can be passed from female mosquitoes to offspring without causing any obvious ecological harm, making it an even more attractive potential tool for malaria control. 

Researchers agree that further studies will be needed to determine the exact mechanisms by which the microbe can be used to control malaria transmission. The next phase of the research will investigate the dynamics of the microbes in large mosquito populations in screen house ‘semi-field’ facilities.

There have been few examples of microbes affecting malaria transmission in mosquitoes, but similar research exists in dengue. Professor Steven Sinkins from the MRC-University of Glasgow Centre for Virus Research said, “we are already using a transmission-blocking symbiont called Wolbachia to control dengue, a virus transmitted by mosquitoes. The Microsporidia MB symbiont has some similar characteristics, making it an attractive prospect for developing comparable approaches for malaria control”. 

Image Credits: icipe (International Centre of Insect Physiology and Ecology), University of Glasgow.