Malaria transmission blocking

icipe makes new discovery

The possibility of controlling malaria using a newly discovered microbe that blocks transmission of the disease from mosquitoes to people has moved closer to reality with advanced findings by the International Centre of Insect Physiology and Ecology (icipe). In a study published on 28 July 2021 in Frontiers in Microbiology (paper link:, the researchers show that the microbe, Microsporidia MB, can be transmitted sexually between mosquitoes, in addition to being passed from mother mosquitoes to their offspring, as reported in the Centre’s previous study. This breakthrough will allow the efficient spread of the microbe through mosquito populations, thus limiting their ability to infect people with the parasite that causes malaria.

In early 2020, icipe and partners made the groundbreaking finding that malaria mosquitoes containing Microsporidia MB are unable to transmit malaria (paper link: The researchers found the microbe, which is related to fungi, occuring naturally inside the cells of the malaria transmitting Anopheles mosquitoes in parts of Kenya. By studying the ways through which it is propagated between mosquitoes, icipe researchers believe they will be able to develop an effective tool for controlling malaria.

In the recent study, the scientists show that Microsporidia MB is efficiently transferred between adult mosquitoes during mating. Also, the microbe naturally accumulates in the reproductive organs of male mosquitoes, indicating that it has adapted to spread through mosquito populations through mating.

“In last year’s publication, icipe showed that Microsporidia MB is passed from female mosquitoes to their offspring. We have now built on these results to demonstrate that the microbe also has another transmission route; from adult to adult,” notes Tracy Maina, an icipe MSc student involved in the research.

“When considering the use of the microbe as a tool for malaria control, the key challenge is increasing Microsporidia MB levels in wild mosquito populations. Therefore, unearthing a new transmission route is of great significance,” adds Dr Jeremy Herren, icipe scientist who led the study.

Feasible strategy

Herren and his team plan to use these results as part of a strategy to increase the spread of Microsporidia MB through mosquito populations in locations in Kenya, thus controlling the spread of malaria in humans. In particular, the researchers are exploring the feasibility of releasing male mosquitoes laden with Microsporidia MB in areas of high malaria transmission. As male mosquitoes do not bite people, they do not pose any malaria-transmission risk. These males would continue with their natural life cycle, infecting wild female mosquitoes with the microbe, which would in turn infect their offspring with the malaria blocking trait. Targeted release of infected male mosquitos and the spread to females and their offspring could initiate a continuous infection cycle across mosquito generations. The result would be a largely self-maintaining and sustainable strategy for malaria control.

Malaria continues to be a major health threat across Africa, with this region accounting for 93% of the global malaria deaths. Since 2005 there has been unprecedented success in malaria control, but progress has stagnated in more recent years with case levels remaining the same between 2014 and 2016 and increasing between 2016 and 2017. There is a vital need for new tools to achieve targets for malaria control and eradication.

Notes for Editors

Research details: Nattoh G., Maina T., Mbaisi L., Mararo E., Makhulu E.E., Teal E., Paredes J., Bargul J., Mburu D. M., Onyango E.A., Magoma G., Sinkins S.P., Herren J.K. (2021) Horizontal transmission of the symbiont Microsporidia MB in Anopheles arabiensis. Frontiers in Microbiology, Volume 12 (Article 647183).

Research collaborators: Pan African University Institute for Basic Sciences Technology & Innovation, Nairobi, Kenya; MRC-University of Glasgow Centre for Virus Research, UK.

Funding: This research was supported by Open Philanthropy Project [SYMBIOVECTOR Track A], the BBSRC [BB/R005338/1, sub-grant AV/PP015/1]. G.N. was supported by the African Union under the Pan African University Institute for Basic Sciences Technology & Innovation (PAUSTI) postgraduate scholarship. We acknowledge icipe’s core donors: Swiss Agency for Development and Cooperation (SDC), Switzerland; Swedish International Development Cooperation Agency (Sida), Sweden; UK’s Foreign, Commonwealth & Development Office (FCDO); Ministry of Education, State Department of University Education and Research, Kenya; and Government of the Federal Democratic Republic of Ethiopia.

The International Centre of Insect Physiology and Ecology ( Our mission is to help alleviate poverty, ensure food security, and improve the overall health status of peoples of the tropics, by developing and disseminating management tools and strategies for harmful and useful arthropods, while preserving the natural resource base through research and capacity building.

Open Philanthropy ( identifies outstanding giving opportunities, makes grants, follows the results, and publishes its findings. Its mission is to give as effectively as it can and share the findings openly so that anyone can build on them.