Spermless mosquitoes could halt malaria spread: study

13 Aug 2023
The Independent
Malaria is spread to humans by female mosquitoes who suck blood in order to help their offspring grow, but British scientists said Monday that introducing spermless males could halt the deadly disease.

Scientists at Imperial College London said that by genetically tweaking male mosquitoes to produce no sperm, females would still mate with them but would lay unfertilized eggs that would not hatch into mosquito larvae.

Since the females of the species Anopheles gambiae sensu stricto, the main type responsible for spreading malaria in Africa, mate only once in their lives, the discovery could have broad implications for a disease that kills nearly 800,000 people per year.

"This study strongly suggests that they cannot tell the difference between a fertile and a spermless mate," said Flaminia Catteruccia, lead author of the study in the Proceedings of the National Academy of Sciences.

Scientists created 100 sterile males by injecting a protein into mosquito eggs that disrupted the development of the males' testes, but did not affect any of their other behaviors or sexual functions.

Observing their mating processes in a lab, they found that the males still produced seminal fluid and the females mated with them as usual. 

The females acted just they way they do in normal circumstances, eating a blood meal after mating and laying a batch of eggs. They did not seek out a second mating attempt even though their eggs produced no offspring.

"This is an exciting time with modern genetics providing a series of new ideas about how to control the major insect vectors of human disease, including the mosquito Anopheles gambiae - perhaps the single most dangerous insect species for mankind," said co-author Charles Godfray, from the University of Oxford.

"A number of these techniques involve disrupting natural mating patterns and to get these to work a really good understanding of mosquito mating and reproduction is essential."

Malaria claimed 781,000 lives in 2009, according to the UN's World Health Organization (WHO), which is heading efforts to distribute insecticide-treated mosquito nets and to spray reproduction sites.

About 90 percent of malaria deaths each year occur in Africa and 92 percent of those are children aged under five.