Portugal deploys sterile mosquitoes to combat disease transmission

Key Takeaways

• Portugal released 30,000 sterile male Asian tiger mosquitoes in Lisbon, bringing the total deployed to 60,000.

• The method relies on sterile males competing with fertile males, reducing the reproduction rate without pesticides.

• A subsequent comparative study is planned for May if the initial observations on mosquito dispersal and survival prove successful.

Testing new methods for mosquito control

Portugal recently released 30,000 sterile male Asian tiger mosquitoes in Lisbon to reduce populations of the species known to carry dengue, Zika, and yellow fever. The deployment in Alvalade marked the final release of this current phase, bringing the total number of sterile mosquitoes released in Portugal to 60,000. Male mosquitoes do not bite; they exist to mate. By flooding the wild population with sterile males, they compete with fertile males, and females that mate with them fail to reproduce, leading to a drop in the population without using pesticides or genetic modification.

“When we release them into areas where there is a population of this mosquito, they will essentially compete with the male mosquitoes that are already there, the wild mosquitoes,” said Afonso Moreira, the project’s lead researcher and a public health doctor at the Francisco George Public Health Unit. He added that the sterilization method is proven and safe, having a strong track record in agricultural pest control.

Evaluating spread and survival

The immediate focus of researchers is to determine how far the released mosquitoes spread and how long they survive in a city setting. If these survival and dispersal metrics are satisfactory, a comparative study will begin in May to measure reproduction rates in treated areas compared to those managed with traditional methods. Moreira emphasized that while this program creates internal pressure on the mosquito population, it is not a standalone solution, and efforts to remove standing water and breeding habitats must continue alongside the sterile male releases. Fewer mosquitoes ultimately mean reduced opportunities for the transmission of dangerous pathogens.