Toxic sperm is intended to prevent female yellow fever mosquitoes from spreading infectious diseases such as dengue, chikungunya and Zika. Photo: ImageSelect.
Genetically engineered male fruit flies shorten the lifespan of females by passing on toxic sperm. The aim is to reduce the spread of mosquito-borne infectious diseases.
Australian researchers have developed a new method that causes female insects to die significantly sooner after mating (Nature Communications, 7 January). The effect is caused by the sperm they encounter: it comes from genetically engineered males and contains toxins. The Australians have dubbed the method the Toxic Male Technique. The new method acts within the same generation of insects, whereas current genetic control methods only affect the offspring of engineered mosquitoes. With this new method, the researchers hope to contribute to the fight against diseases such as dengue, chikungunya and Zika, which are spread by female mosquitoes of the species Aedes aegypti. Because of pesticide resistance, genetic manipulation is an attractive alternative as a control method.
Fruit flies
The researchers carried out their work in fruit flies, of the species Drosophila melanogaster. They manipulated the genes of male fruit flies so that these produced toxins that ended up in their sperm. The toxins are derived from sea anemones and spiders, and are intended to be toxic only to specific insect species and not to vertebrates. The lifespan of females was reduced by between 37 and 64 per cent after mating. Based on computer models, the researchers expect the technique to work in A. aegypti as well; compared with existing insect control techniques, the number of blood meals taken by affected females is predicted to decrease substantially.
Schematic representation of the difference between ‘traditional’ mosquito control using genetic techniques (A) and the Toxic Male Technique (TMT) proposed by the researchers (B). Illustration: Created with BioRender by Maselko, M. (2024).
Lifespan
Infectious disease epidemiologist Teun Bousema, Professor of Epidemiology of Tropical Infectious Diseases at Radboud University Medical Centre and not involved in the research, describes the study as ‘a technically impressive piece of work’. Bousema is drawn to the fact that the authors focus on shortening the lifespan of the insects to prevent disease transmission, rather than eradicating the population. ‘The claims about reduced disease transmission are ambitious: effectiveness still needs to be demonstrated in Aedes mosquitoes. It is good that the researchers are thinking in this direction: in Indonesia, Aedes mosquitoes are being engineered using the Wolbachia bacterium so that they are less able to transmit dengue,’ says Bousema. ‘Genetic modification is also being used in the fight against malaria. I therefore understand the desire to extrapolate to vector insects that are relevant to humans. Nevertheless, the first step is to show that this method works – and works in the same way – in Aedes and malaria mosquitoes. The computer analyses for the Aedes mosquitoes, as the authors themselves note, were carried out under the assumption of the most ideal conditions. Moreover, this article lacks information on whether the lifespan of the mosquitoes is reduced sufficiently for death to occur before they can transmit disease.’
Risk
According to Bousema, broader debates are ongoing about the implementation of methods that make use of genetically engineered mosquitoes. ‘The question is always: is the perceived risk of genetically modifying the insect much smaller than the risk posed by the disease?’
See also:
–Fatal Attraction: Engineered Male Mosquitoes Could Transform Disease Control – website Macquarie University, Sydney (10 January 2025)