Malaria, a life-threatening disease typically found in tropical climates, is transmitted through the bite of a mosquito that was infected with the Plasmodium parasite. Symptoms include fever, chills, headache, anemia, convulsions, and sweating.
In 2018, the World Health Organization (WHO) estimated 228 million cases of the mosquito-borne disease, and that they would lead to 405,000 deaths. The WHO, governments, and researchers have long been working on different approaches to tackle the disease, but progress has stalled in recent years.
But what if we could go to the source and prevent the mosquitoes from being infected? That was the question researchers from Kenya and the UK asked themselves, having found a microbe that protects the mosquitoes and could thus help to control the disease.
The malaria-blocking microbe, called Microsporidia MB, was discovered by the researchers on the shores of Lake Victoria, Kenya. They couldn’t find a single mosquito carrying the microbe and also harboring the malaria parasite there.
The protection given by the microbe was later confirmed by further laboratory analysis. Microsporidias are fungi, or at least closely related to them, and most are parasites. However, this new species may be beneficial to the mosquito.
“The data we have so far suggest it is 100% blockage, it's a very severe blockage of malaria,” Dr Jeremy Herren, from the International Centre of Insect Physiology and Ecology in Kenya told the BBC. He added: “It will come as a quite a surprise. I think people will find that a real big breakthrough.”
The idea that a mosquito microbe could be stopping the transmission of a disease isn't exactly new. Wolbachia, a genus of bacteria that naturally occurs in mosquito populations, has shown incredible potential for wiping out dengue and other mosquito-borne infections.
This new research is currently in its early stages. Because Microsporidia MB is passed down the maternal line, once it's in the mosquito population, it's unlikely to be going anywhere. The team found that some mosquito populations in some areas they tested already had 9% of individuals infected with the malaria-busting microbe.
Microsporidia MB could be priming the mosquito's immune system, so it is more able to fight off infections. Or the presence of the microbe in the insect could be having a profound effect on the mosquito's metabolism, making it inhospitable for the malaria parasite.
The researchers are investigating two main strategies for increasing the number of infected mosquitoes. Microsporidia forms spores that could be released en masse to infect mosquitoes. Or male mosquitoes (which don't bite) could be infected in the lab and released into the wild to infect the females when they have sex
“It's a new discovery. We are very excited by its potential for malaria control. It has enormous potential,” Prof Steven Sinkins, from the MRC-University of Glasgow Centre for Virus Research, told the BBC.
The scientists need to understand how the microbe spreads, so they plan to perform more tests in Kenya. However, these approaches are relatively uncontroversial as the species is already found in wild mosquitoes. It also would not kill the mosquitoes, so it would not have an impact on species that rely on them for food.
The research was published in Nature Communications.