Scientists at the International Center for Insect Physiology (icipe) and Ecology in Kenya and the University of Glasgow have discovered a unicellular microbe that prevents mosquitoes from carrying and transmitting malaria parasites.
The microbe, named Microsporidia MB, has been found to be naturally occurring in mosquito populations in Kenya.
Malaria is caused by a species of parasite called Plasmodium and causes 200 million cases and 400,000 deaths annually. The disease is spread when someone is bitten by a mosquito infected with Plasmodium parasites.
Although the mosquito is not affected by the parasites, it carries the virus in saliva, which is then injected into the victim before blood is drawn.
Currently, preventive 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 give hope for a new control method.
The microbe identified by the researchers prevents the Plasmodium parasites from colonizing the mosquito’s salivary glands.
Scientists gave mosquitoes a food source containing the malaria virus with the microbe and found that the presence of Microsporidia MB prevented the virus from establishing itself.
Nine percent of the mosquito populations tested already had the Microsporidia MB microbe in the midgut. The relationship between the microbe and the mosquito is considered to be symbiotic – which is mutually beneficial.
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“Healthy insects often have microbial symbionts in their bodies and cells,” said Dr. Jeremy Herren, the icipe scientist who led the study. “These symbionts can have a significant impact on the biology of their hosts. Our team is trying to learn more about these types of microbes in insects that are important to human health.”
The microbe has been found to enter the ovaries of female mosquitoes and pass to their offspring without harm, hopefully allowing Microsporidia MB to spread quickly through the mosquito population.
However, more studies are needed to determine exactly how the microbe can be used to fight malaria infections, Herren said.
Readers’ questions and answers: Could mosquitoes deliver malaria vaccines?
Asked by: John Leslie Boden, Northampton
Unfortunately, despite decades of intensive research and development, there is no vaccine against malaria.
However, more than 20 potential malaria vaccines are in the experimental phase to efficiently eradicate certain stages in the life cycle of Plasmodium – the malaria-causing parasite that some mosquitoes carry and which we accidentally become infected with.
There is a proof-of-concept study showing that mosquitoes can deliver a vaccine candidate through their saliva. How much they shed, however, depends on how often they bite someone. Hence, it would be incredibly difficult to deliver the right dose of a vaccine.