Scientists have discovered a bacterium that lives in mosquitoes around Lake Victoria, and appears to block malaria (which is caused by a parasite that's also carried by mosquitoes). Researchers could not find a single mosquito that harbored both this bacterium and the malaria parasite. In the lab, mosquitoes were exposed to this microbe and then were protected against the malaria parasite (Plasmodium). Reporting in Nature Communications, an international team of researchers has suggested that this microbe, called Microsporidia MB, might be able to help stop the disease from infecting humans.
"Further studies will be needed to determine precisely how Microsporidia MB could be used to control malaria," noted Jeremy Herren, a researcher at the International Center for Insect Physiology and Ecology and the University of Glasgow Center for Virus Research.
Female mosquitoes can carry several different species of the malaria-causing Plasmodium parasite, which has a complicated life cycle that is only completed when the parasite reaches a human host. The World Health Organization estimated that globally, 228 million people were infected with malaria in 2018. The disease kills around 400,000 people every year.
The Microsporidia MB microbe was found when researchers were studying mosquitoes in the Lake Victoria area in Kenya. This bacterium lives in the gut and genitals of an estimated five percent of insects in the region. Once infected with Microsporidia MB, mosquitoes seem to carry it for the rest of their lives.
It's not yet known how the microbe prevents malaria from infecting a mosquito. It may help boost their immune system or make metabolic changes that are detrimental to the Plasmodium parasite.
The research team estimated that 40 percent of mosquitoes in any given area would need to carry the microbe to stop malaria from spreading. The microbe can be passed naturally from one mosquito to another and from female to offspring.
The scientists have begun to consider how Microsporidia MB might be encouraged to spread among mosquitoes. One approach would involve releasing Microsporidia MB spores in the hopes that many mosquitoes would end up infected. Another strategy is to intentionally infect male mosquitoes, who don't attack people. Instead, they would spread the microbe to females when they mated. Mosquitoes would (theoretically) not be killed in these processes.
Similar methods are used with a bacterium called Wolbachia to try to stop the mosquito-borne disease Dengue fever from spreading.
"The next phase of the research will investigate Microsporidia MB dynamics in large mosquito populations in screen house 'semi-field' facilities," Herren explained. "The results of these studies will give us key information that will be used to determine how we could then disseminate Microsporidia MB for malaria control."