Researchers have introduced a novel approach to combat female mosquitoes by genetically modifying male insects to carry a lethal toxin in their sperm. This method has shown success in laboratory settings.
Currently, insecticides are released into the environment, affecting not only target pests but also other organisms. The new strategy aims to deliver toxins more precisely through mating.
The team led by Maciej Maselko from Macquarie University in Sydney has detailed their findings in the journal Nature Communications. In initial tests, they did not use the yellow fever mosquito (Aedes aegypti), which they aim to control long-term, but rather the well-studied model organism Drosophila melanogaster (fruit fly). They inserted the genetic instructions for producing a toxin derived from a sea anemone into the genome of male fruit flies. Other males were engineered to produce a toxin from the Brazilian wandering spider. Female fruit flies mating with these modified males exhibited a reduced lifespan of approximately 40 to 60 percent.
A model calculation for the application to the yellow fever mosquito indicated that the reduced survival rate could lead to a similar decrease in biting rates by around 40 to 60 percent. Furthermore, this method is expected to be faster and more effective than alternative genetic approaches that only impact subsequent generations.
However, transferring this technique to Aedes aegypti and other disease-carrying insects presents challenges. Ensuring that the toxin affects only the female and not the male requires precise control over where the genetic instructions are expressed. This is easier to achieve in the well-studied fruit fly than in other species.
Since males kill the females they mate with, there is minimal risk of the new genes spreading within the population. This addresses a significant drawback of other methods that release genetically modified organisms into the environment. However, complex techniques are necessary for breeding the genetically modified males, as the expression of the genetic instructions must be suppressed until the males are released into the wild.
Experts assess the risk to other species that might consume the modified males as low: the toxin acts when its small molecules diffuse from the female's genital tract into the body fluids, causing damage. In a predator's digestive tract, the toxin remains largely ineffective.