Scientists genetically modify mosquitoes to prevent malaria-carrying females reproducing

Malaria continues to kill 445,000 people each year
Malaria continues to kill 445,000 people each year Credit: Carl Knoderer/EyeEm

Researchers have stopped malaria-spreading mosquitoes from reproducing via genetic modification, paving the way to their eventual elimination in the wild. 

Scientists at Imperial College, London completely blocked the reproductive ability of the Anopheles gambiae mosquito, which spreads malaria, eliminating the lab population within seven to 11 generations using a technique called gene drive.

Despite significant reductions in cases in the last two decades, malaria remains the biggest killer of children under five in Africa. In 2016 there were 216 million cases of the disease worldwide, resulting in an estimated 445,000 deaths overall. 

 "This breakthrough shows that gene drive can work, providing hope in the fight against a disease that has plagued mankind for centuries,” said Professor Andrea Crisanti, lead researcher from the Department of Life Sciences at Imperial.

“There is still more work to be done, both in terms of testing the technology in larger lab-based studies and working with affected countries to assess the feasibility of such an intervention.”

The breakthrough comes weeks after a team in Burkina Faso became the first in Africa to receive permission to release 10,000 sterile male mosquitoes into the wild. This release will have no effect on malaria transmission, but will establish how modified mosquitoes interact with the natural population. 

This latest study is a major step towards eradicating malaria-carrying mosquitoes in the wild, by spreading female infertility. 

The scientists targeted the double-sex gene, which determines the mosquito's sex, through a technique called gene drive. The technique spreads a gene, or particular suite of genes, through a population via reproduction. 

Males who carried the genetic modification saw no changes, and neither did females with only one copy of the gene. But females with two copies showed both male and female characteristics, failed to bite and did not lay any eggs. 

Previous attempts to suppress the mosquito population through gene drives have been unsuccessful because the insects have developed mutations which are resistant to the genetic modifications.

These mutations have then been passed onto offspring, preventing the reduction of the mosquito population. 

But the scientists have targeted the double-sex gene because it is highly “conserved”, meaning that random mutations are lethal to the organism and would not be passed on. In the lab-based experiments, the gene drive saw the genetic modifications transmitted nearly 100 per cent of the time. 

"It will still be at least five to 10 years before we consider testing any mosquitoes with gene drive in the wild, but now we have some encouraging proof that we're on the right path,”  said Professor Crisanti.

“Gene drive solutions have the potential one day to expedite malaria eradication by overcoming the barriers of logistics in resource-poor countries."

The researchers also said that additional experiments to investigate the efficacy and stability of the gene drive in conditions were necessary. This includes testing in more realistic settings, such as conditions mimicking tropical environments, and among larger mosquito populations. 

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