Scientists at the shores of Lake Victoria in Kenya have found a parasite in wild Anopheles mosquito populations that protects the insect from malaria infection. The organism, which they have called microsporidia MB, is a spore-forming unicellular parasite closely related to fungus. It doesn’t harm the mosquito in any way and is, therefore, a beneficial symbiont.
Jeremy Herren, the lead researcher on the project from the International Centre of Insect Physiology and Ecology (icipe) in Kenya, said:
The bodies of all animals are inhabited by microbes which are either detrimental – in other words, pathogens; or neutral/beneficial symbionts. Healthy insects often have microbial symbionts inside their bodies and cells, which can have major effects on the biology of their hosts.
Microsporidia MB is found in the guts and genitals of mosquitoes and is transmitted from a mother to her offspring. It doesn’t spread from insect to insect in a pathogenic fashion. Since the microbe somehow actively prevents Plasmodium infection in mosquitoes, it could be employed for malaria control strategies to reduce transmission of the disease into human populations.
Dr. Herren told the BBC:
The data we have so far suggest it is 100% blockage, it’s a very severe blockage of malaria.
The researchers still don’t know how the species protects the mosquito from the malaria parasite. Further research is required to determine that. Nevertheless, the discovery is far more appealing than the previous fungus solution to curb malaria – which involved a genetically-modified organism being released to control the mosquito-driven disease transmission. The genetically modified fungus wiped out the malaria-carrying mosquitoes without harming any other living organism, but many remained skeptical of the approach.
Microsporidia MB, on the other hand, is entirely natural and already present in the wild. Dr. Herren said:
Further studies will be needed to determine precisely how Microsporidia MB could be used to control malaria. The next phase of the research will investigate Microsporidia MB dynamics in large mosquito populations in screen house ‘semi-field’ facilities. 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.
The disease imposes a massive burden on sub-Saharan Africa, with approximately 93% of all 228 million malaria cases and 94% of deaths in 2018 occurring there. More than 400,000 people die annually, with two-thirds of them being children under the age of five. The World Health Organisation (WHO) recently stressed its concern about the coronavirus pandemic interfering in the efforts against malaria.
The WHO reported:
Under the worst-case scenario, in which all insecticide-treated net (ITN) campaigns are suspended and there is a 75% reduction in access to effective antimalarial medicines, the estimated tally of malaria deaths in sub-Saharan Africa in 2020 would reach 769 000, twice the number of deaths reported in the region in 2018. This would represent a return to malaria mortality levels last seen 20 years ago.
Enormous progress has been made in the battle against malaria. The fight must continue. New tools are needed to accelerate development further. Microsporidia MB holds excellent promise as such. Also, the antimalarial drug called Ivermectin made from bacteria has been found to reduce transmission rates. The medication makes the blood of people injected with it lethal to mosquitos. However, that requires repeated medication.
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