Scientists identify organisms in mosquitoes that can help fight malaria

Scientists have identified a microbe  (organism) in mosquitoes that is sexually transmitted and could be used in the fight against malaria. The microbe could deactivate their ability to pass the disease on to humans.

The 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) that it is sexually transmittable between mosquitoes.

In a study published on July 28 in a scientific journal Frontiers in Microbiology, 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 previously reported in the centre’s 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,” said Icipe in a statement.

In early 2020, Icipe and partners made the groundbreaking discovery that mosquitoes containing Microsporidia MB are unable to transmit malaria.

Fungi

The researchers found the microbe — a fungi —occurs naturally inside the cells of the malaria transmitting anopheles mosquitoes in parts of Kenya.

Mosquitoes were collected in Ahero, Mwea, Kilifi and Malindi.

In the recent studies that have involved intricate processes such as rearing virgin mosquitoes, infecting them with the fungi and forced mating experiments, monitoring copulation, collection of seminal secretions produced by the male, then female recipients being allowed to feed on a human arm, lab analytics, among other attendant tasks, the scientists have now found 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 spreading across mosquito populations through mating.

“Previous studies by 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,” said Tracy Maina, an Icipe MSc student involved in the research.

By studying the ways through which the microbe is propagated between mosquitoes, Icipe researchers believe they will be able to develop an effective tool for controlling malaria.

“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,” added Icipe lead scientist in the study, Dr Jeremy Herren.

The team has said it plans to use these results as part of a strategy to increase the spread of Microsporidia MB through mosquito populations in locations in Kenya, to control the spread of malaria in humans.

Africa continues to carry a disproportionately high share of the global malaria burden.

In 2019, there were 229 million malaria cases. The continent accounts for 93 per cent of the 409,000 global malaria deaths. In Kenya, every two minutes, a child under five dies of malaria.

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.

Male mosquitoes

Specifically, 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,” said Icipe.

Once released, infected male mosquitoes will mate with females, and any offspring produced will never be able to transmit the disease either, in what is hoped could set off a ripple effect of the contagion.

“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 a sustainable strategy for malaria control,” noted Icipe.