Insecticide-resistant mosquito discovered

A newly discovered ‘super mosquito’ has the ability to survive the insecticides used to treat bed nets which are key to preventing the spread of malaria in humans, scientists say. Interbreeding of two malaria mosquito species in the West African country of Mali has resulted in a “super mosquito” hybrid that is resistant to insecticide-treated bed nets.

“It’s ‘super’ with respect to its ability to survive exposure to the insecticides on treated bed nets,” said medical entomologist Gregory Lanzaro of University of California-Davis, who led the research team.

The research “provides convincing evidence indicating that a man-made change in the environment — the introduction of insecticides — has altered the evolutionary relationship between two species, in this case a breakdown in the reproductive isolation that separates them,” said Lanzaro.

“What we provide in this new paper is an example of one unusual mechanism that has promoted the rapid evolution of insecticide resistance in one of the major malaria mosquito species,” Lanzaro added.

Anopheles gambiae , a major malaria vector, is interbreeding with isolated pockets of another malaria mosquito, A coluzzii .

Entomologists initially considered them as the “M and S forms” of Anopheles gambiae. They are now recognised as separate species.

“Growing resistance has been observed for some time,” Lanzaro said.

“Recently it has reached a level at some localities in Africa where it is resulting in the failure of the nets to provide meaningful control, and it is my opinion that this will increase,” said Lanzaro.

Lanzaro credits insecticide-treated nets with saving many thousands, probably tens of thousands of lives in Mali alone.

The World Health Organisation’s World Malaria Report indicates that deaths from malaria worldwide have decreased by 47 per cent since 2000. Much of that is attributed to the insecticide-treated bed nets, researchers said. However, it was just a matter of time for insecticide resistance to emerge, experts say. Now there is “an urgent need to develop new and effective malaria vector control strategies,” Lanzaro said.

A number of new strategies are in development, including new insecticides, biological agents — including mosquito—killing bacteria and fungi — and genetic manipulation of mosquitoes aimed at either killing them or altering their ability to transmit the malaria parasite.

The study was published in the journal PNAS . — PTI

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