A single-cell microbe that prevents mosquitos from being able to carry and transmit malaria parasites has been discovered by scientists at the International Centre of Insect Physiology (icipe) and Ecology in Kenya and the University of Glasgow.
The microbe, named Microsporidia MB was found to be naturally occurring in mosquito populations in Kenya.
Caused by a species of parasite called Plasmodium, malaria accounts for 200 million cases and 400,000 deaths annually. The disease is transmitted when someone is bitten by a mosquito infected with Plasmodium parasites.
The mosquito, though not affected by the parasites, carries the virus in its saliva, which is then injected into its victim before blood is drawn.
Currently, preventative measures such as insecticide-treated mosquito nets and insecticide sprays are used to reduce the spread of the disease. However, the results of the study, published in the journal Nature Communications, offer hope of a new control method.
The microbe identified by the researchers stops the Plasmodium parasites from colonising the mosquito’s salivary glands.
Scientists gave mosquitos with the microbe a food source containing the malaria virus and found that the presence of Microsporidia MB prevented the virus from establishing itself.
Nine per cent of the mosquito populations tested already had the Microsporidia MB microbe in their midgut. The relationship between the microbe and the mosquito is thought to be symbiotic – meaning mutually beneficial.
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“Healthy insects often have microbial symbionts inside their bodies and cells,” said Dr Jeremy Herren, the icipe research scientist who led the study. “These symbionts can have major effects on the biology of their hosts, and our team is trying to learn more about this type of microbe in insects that are important to human health.”
The microbe was found to enter the ovaries of female mosquitos and pass onto their offspring without causing any harm, which will hopefully allow Microsporidia MB to spread through the mosquito population quickly.
However, further studies are needed to determine precisely how the microbe could be used to control malaria infections, said Herren.
Reader Q&A: Could mosquitoes deliver malaria vaccines?
Asked by: John Leslie Boden, Northampton
Unfortunately, there is no vaccine against malaria, despite decades of intense research and development.
More than 20 potential malaria vaccines are in their trial phases though, which aim to efficiently eliminate certain stages of the life cycle of Plasmodium – the malaria-causing parasite that some mosquitoes carry and inadvertently infect us with.
There has been a proof-of-concept study that shows mosquitoes could deliver a candidate vaccine through their saliva, but how much they deliver depends on how many times they bite someone, so delivering the right dose of a vaccine would be incredibly challenging.