Activists abuzz over sterilised mosquito test

Scientists in Burkina Faso have deployed a new weapon in the fight against malaria, and waded into a thorny bioethics debate, by letting loose thousands of genetically sterilised mosquitoes.

The experiment is the first outside the lab to release genetically altered mosquitoes in the hope of reducing their ability to spread the often deadly disease.

It works using a technique called a gene drive, which edits and then propagates a gene in a population — in this case to prevent males from reproducing.

Investments in antimalarial drugs, mosquito nets and insecticides have slowed malaria over the past two decades in Africa, which accounts for more than 90% of global cases. But malaria still killed more than 400,000 people across the continent in 2017, and the World Health Organisation (WHO) says progress against the disease is stalling, leading researchers to push for fresh approaches.

“The conventional tools we have at our disposal today have reached their limit,” said Dr Abdoulaye Diabaté, who is running the experiment for Target Malaria, a research consortium backed by the Bill & Melinda Gates Foundation.

One evening in July, Diabaté’s researchers peeled off netting from containers to release about 5,000 male mosquitoes into Souroukoudinga, in western Burkina Faso. The mosquitoes had been injected with an enzyme that sterilises them.

“Our objective is not to eradicate mosquitoes,” said Diabaté, noting that the enzyme targets only the three main species — out of more than 3,500 worldwide — that carry malaria. “The objective is … to reduce the density of these mosquitoes.”

Target Malaria is also developing an enzyme preventing male mosquitoes from passing on X chromosomes. This results in male offspring, reducing malaria as only female mosquitoes bite.

Diabaté said he hopes the new approaches will win approval from national regulators for widespread use.

However, activists in Burkina fear unintended environmental consequences. They point to Burkina’s experiment with genetically modified cotton a few years ago, which farmers said had lowered quality and was ultimately abandoned in favour of conventional seeds.

“We are not going to allow Burkinabes to be used as guinea pigs,” said activist Ali Tapsoba. “If we intoxicate one link in the food chain, we are going to intoxicate the next link.”

Target Malaria says it consults with communities and that research is overseen by national regulatory authorities and an independent ethics committee.

Two months after the mosquitoes were released, Souroukoudinga chief Pascal Traoé said villagers were happy with the experiment.