A Kenyan-British team of scientists has discovered a microbe to stop malaria transmission

An Anopheles stephensi mosquito obtains a blood meal from a human host
An Anopheles stephensi mosquito obtains a blood meal from a human host
Image: REUTERS/Jim Gathany/CDC
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Scientists in Kenya have discovered a novel method with significant potential to completely stop mosquitos from transmitting the parasites which cause malaria in humans.

The team of scientists, mostly from Kenya and the UK, plus one from South Africa, have been studying mosquitoes on the shores of Lake Victoria in Kenya. They discovered that Microsporidia MB, a microorganism that lives in a mosquito’s gut and reproductive tract, completely protects the mosquito from being infected with plasmodium, the parasite that causes malaria.

Microsporidia are fungi, or at least closely related to them. Like plasmodium, which are protozoans, they are also known to live inside mosquitoes as parasites. Mosquitoes inject their saliva into the skin to facilitate blood-feeding. Their saliva sometimes contains plasmodium, which is usually injected together with their saliva resulting in malaria transmission. According to the study, the Microsporidia MB reduces the establishment of the Plasmodium falciparum parasite in the guts of the mosquitoes, and impairs the colonization of the salivary glands by the parasite.

Scientists believe this makes the Microsporidia MB a realistic candidate as an eco-friendly and sustainable strategy to replace harmful mosquito population with harmless ones and to help with prospects for malaria control. The hope is that by infecting mosquitoes in a region with Microsporidia they will no longer be able to infect humans with malaria parasites.

This strategy has been demonstrated before in a city in northern Australia where mosquitoes infected with Wolbachia, a bacterium, were deployed on a large scale, effectively stopping all outbreaks of dengue fever for more than four years.

Last month, the World Health Organization reported that progress in the fight against malaria, which kills 400,000 people annually, had stalled as both the parasite and mosquitoes were showing increasing resistance to treatments.

The discovery of the microbe comes as current malaria control measures are starting to be seen as insufficient or ineffective. There have been reports of drug resistance, such as Artemisinin resistance, in several regions and insecticide resistance in 73 countries in 2019. The new RTS,S malaria vaccine approved in 2015 has low efficacy and only decreased malaria cases by 39% and severe cases by 29% in clinical trials.

This efficacy of the vaccine is low compared to 85% to  95% for most routine vaccines for children. There has been no significant reduction in the annual numbers of malaria cases since 2014. This has led to concerns that if better methods are not developed to control the disease, the progress achieved so far may be reversed.

Sub-Saharan Africa carries a disproportionately high share of the global malaria burden. In 2018, an estimated 228 million cases of malaria occurred worldwide, with Sub Saharan Africa accounting for 93% of the cases and 94% of deaths. The disease, spread by female Anopheles mosquitoes, is already costing the continent about $12 billion a year in direct losses and saddles families with crippling medical costs.

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