By Sharon Atieno

With malaria claiming 400,000 lives every year, researchers have identified a microbe in malaria mosquitoes that is capable of blocking transmission of the disease from the insects to people.

In a study published in Nature Communications journal, the scientists from the International Centre of Insect Physiology and Ecology (icipe) and the University of Glasgow, UK, report that the microbe, which they have named Microsporidia MB, was found in anopheles mosquitoes in a study conducted mainly on the shores of Lake Victoria in Kenya.

The researchers established that mosquitoes carrying Microsporidia MB do not harbour malaria parasites either in nature, or after experimental infection in the laboratory. The research also showed that Microsporidia MB is passed from female mosquitoes to their offspring at high rates, and the microbe does not kill or cause obvious harm to the mosquito host.
“The bodies of all animals are inhabited by microbes which are either detrimental – in other words pathogens; or neutral / beneficial symbionts,” explains Dr Jeremy Herren, current icipe Scientist who led the study while jointly affiliated with icipe and the University of Glasgow, UK.

 “Healthy insects often have microbial symbionts inside their bodies and cells, which can have major effects on the biology of their hosts. At icipe, my team’s research is focused on this type of microbial symbiont, especially when they may be interfering with transmission of diseases by insects.”

 Despite the new microbe being naturally found at relatively low levels in malaria mosquitoes in Kenya, the researchers believe that there may be ways to increase the proportion of mosquitoes that carry it, to block their capacity to transmit malaria.

This type of transmission-blocking intervention has been shown to have transformative potential for controlling Dengue, a disease transmitted by Aedes aegypti mosquitoes. Until now, there have been few examples of microbes that affect malaria transmission mosquitoes.  “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,” adds Lilian Mbaisi, a Kenyan scholar who was involved in the study, as part of her MSc research at icipe, registered at the University of Nairobi.

The authors note that these two attributes are key, as they could enable the spread of symbionts through mosquito populations, and their maintenance across many malaria transmission seasons.

However, the researchers stress that 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 the dynamics of the microbes in large mosquito populations in screen house ‘semi-field’ facilities.