The predator cues emitted by the Backswimmer, a mosquito larvae predator, trigger a stress response in the mosquitoes, which impairs their immune system.
Photo © E. Van Herk

Two weeks ago we saw a chemically-baited, solar-powered trap for mosquitos implemented in Kenya. New research – conducted only in the laboratory so far – has shown the potential for another chemical cocktail to be used in a very different way for mosquito control, hopefully in a manner that can reduce quantities of pesticide applied in eradication efforts. From the EurekAlert press release by the Belgian University of Leuven:

Existing strategies for mosquito control often involve the use of pesticides that harm the environment. These pesticides are increasingly less effective as well, as insects can become resistant to existing products relatively quickly.

Biopesticides are a possible alternative. The most commonly used biological pesticide is the Bacillus thuringiensis israelensis (Bti) bacteria. Unfortunately, mosquitoes are already developing a resistance to this pesticide as well. This means we have to keep increasing the dose of Bti to kill mosquitoes, so that this biological substance, too, is beginning to harm the environment.

Under the supervision of Professor Robby Stoks, KU Leuven doctoral student Lin Op de Beeck set out to find a new strategy in the fight against mosquitoes. “We already knew that chemical substances emitted by the backswimmer – a natural enemy of mosquito larvae in the water – trigger a stress response in mosquitoes. This stress response, in turn, suppresses the mosquito’s immune system,” says Op de Beeck. “Scientists have recently found a way to produce a synthetic version of these chemical substances known as predator cues. We discovered that this synthetic version triggers a stress response in the mosquitoes and impairs their immune system, just like the natural predator cues.”

This gave the researchers the idea to combine these synthetic predator cues with the biological pesticide Bti. “We developed a cocktail of predator cues and a low, non-lethal dose of Bti,” Lin Op de Beeck continues. “The predator cues trigger extra stress, so that the Bti had a strong impact despite its lower dose. As a result, the mortality rates among mosquitoes were high.”

As the predator cues of the backswimmer also have an impact on their targets’ immune system, the cocktail weakens the mosquitoes and larvae that it fails to kill. “The surviving mosquitoes and mosquito larvae will probably have a shorter lifespan, so that the parasites they transmit don’t have the time to complete their incubation period,” says Op de Beeck. “As a result, the mosquitoes will transmit less diseases.”

An additional advantage of this combined strategy is that synthetic predator cues of the backswimmer are not so difficult to produce, making the production of the Bti cocktail relatively easy and cheap.

Read the full press release here.