Malaria is a tropical disease affecting humans and animals through the bite of a mosquito, causing fatalities when it is not diagnosed and treated promptly. The majority of malaria cases occur in Africa and India, caused by the transmission of the single-celled Plasmodium parasite from the bite of female Anopheles mosquitoes, also known as a ‘vector’.
The main strategy in the fight against malaria is vector control using mosquito nets treated with insecticide, reducing the incidence of this disease by approximately 40 percent over the past fifteen years. Unfortunately, this figure remained unchanged between 2014 and 2016, indicating this control measure is insufficient. Therefore, new strategies to cull specific mosquito populations or their ability to transmit Plasmodium are desperately needed.
Halting the malaria parasite
Now, a study from researchers led by the University of Glasgow identifies a new species of microbiota in mosquitoes, dubbed Microsporidia MB, possessing the capacity to stop the vertical transmission of Plasmodium in mosquitoes from mother to offspring.
The team states the Microsporidia MB fungi does not appear harmful to the mosquitoes, indicating an increase of the insects infected with the parasite may be a highly effective and ecologically sound strategy for stemming the spread of malaria. The opensource study is published in the journal Nature Communications.
Previous studies show the use of a mosquito-borne microbe to stop the transmission of a disease is a proven strategy with the naturally occurring Wolbachia bacteria exhibiting the enormous potential to wipe out dengue. Dengue is currently the most prevalent mosquito-borne disease in the world with an estimated 50 million cases per annum leading to tens of thousands of fatalities.
The successful introduction of a life-shortening strain of Wolbachia into the dengue vector Aedes aegypti to halve adult lifespan has recently been reported. However, in the Anopheles mosquito, there are limited reports of inherited symbiotic microbiota able to stop transmission of the Plasmodium parasite. The current study discovers the Microsporidia MB symbiotic microbe in Anopheles mosquitoes endowed with similar characteristics to the Wolbachia bacteria.
A fungus to control malaria
The current study identifies the fungus Microsporidia MB in Anopheles mosquitoes around the shores of Lake Victoria in Kenya. The parasite was found primarily in the gut and genitals of approximately 5 percent of the local Anopheles mosquito population.
Results show Anopheles mosquitoes containing the microorganism do not carry malaria parasites, either in their natural habitat or after deliberate infection in the lab. Data findings show Microsporidia MB is passed from female Anopheles mosquitoes to their offspring without causing harm to the mosquito host.
The lab stresses they are still unsure as to how Microsporidia MB blocks the Plasmodium parasite and hypothesize it may boost the mosquito’s immunity, or alter the vector’s metabolism, making their bodies less hospitable to malarial parasites.
They end with two strategies for spreading Microsporidia MB involving the release of large numbers of spores to spread among mosquitoes or perhaps infecting male mosquitoes and releasing them into the wild to vitiate females when they mate.
The team surmises they offer a mode of malaria control similar to the one used to control dengue, involving the use of inherited mosquito-borne microbes to block Plasmodium transmission. For the future, the researchers state they now plan to evaluate Microsporidia MB in large mosquito populations in near-natural settings.
Source: United Press International, Inc.
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