Newly discovered parasitic fungus blocks malaria infecting mosquitoes

A newly discovered microbe identified in wild mosquito populations in Kenya has been found to protect the insects from malaria infection. It’s hypothesized the microbe could be recruited for malaria control strategies to limit transmission of the disease into human populations.

“The bodies of all animals are inhabited by microbes which are either detrimental – in other words pathogens; or neutral/beneficial symbionts,” explains Jeremy Herren, lead researcher on the project. “Healthy insects often have microbial symbionts inside their bodies and cells, which can have major effects on the biology of their hosts.”

The previously unknown microbe was discovered in wild populations of Anopheles mosquitoes on the shores of Lake Victoria in Kenya and belongs to a group of organisms known as microsporidia, spore-forming unicellular parasites closely related to fungus.

The species was named Microsporidia MB, and it was detected in less than 10 percent of local mosquitoes. Found in the guts and genitals of mosquitoes, the researchers learned Microsporidia MB is vertically transmitted, meaning it doesn’t spread from insect to insect in a pathogenic fashion, but rather it only seems to be transmitted from a mother to her offspring.

“We were excited to find that the Microsporidia MB symbiont is transmitted from mother mosquitoes to their offspring, and that the microbe does not compromise the ability of mosquitoes to survive,” says Lilian Mbaisi, a Kenyan researcher from the International Centre of Insect Physiology and Ecology (icipe).

The research revealed no mosquito found in the wild with Microsporidia MB was also infected with Plasmodium, the parasite responsible for malaria. Subsequent laboratory experiments revealed the microbe seemed to actively prevent Plasmodium infection in mosquitoes.

This study presents one of the first times a relatively harmless microbe that prevents malaria infection in mosquitoes has been discovered. The fact the microbe seems to cause no observable harm to the insect, and is easily transmissible from mother to offspring, makes it an ideal candidate for malaria-control strategies in regions struck by the troubling disease.

This would not be the first time microbes have been explored as a way of controlling mosquito-driven disease transmission. A naturally occurring bacterium called Wolbachia has been extensively used to control mosquito populations in the United States and Australia.

It's very early days for the research, so exactly how the newly discovered microbe protects a mosquito from the malaria parasite is unclear at this stage. But the discovery optimistically points to novel malaria control strategies in the future, either through a release of Microsporidia MB spores within a local population, or via a more targeted delivery of mosquitoes harboring the microbe into the wild.

"It's a new discovery,” says Steven Sinkins, a researcher from the University of Glasgow working on the project. “We are very excited by its potential for malaria control. It has enormous potential.”

The new study was published in the journal Nature Communications.

Sources: University of Glasgow, icipe