In total, 60,000 mosquitoes have already been released, with the last release of this type of insect taking place on 24 September, Afonso Moreira, a Public Health physician at the Francisco George Public Health Unit of the Santa Maria Local Health Unit, told Lusa.

Sterilized mosquitoes

The official explained that the released mosquitoes belong to the species ‘Aedes albopictus’, known as the Asian tiger mosquito, and that, “because they are males”, they do not bite, since only females need blood.

“They were sterilised using a proven and safe technique, and when we release them into an area where there was a population of this mosquito, they will ultimately compete with the male mosquitoes that already exist in the area, the wild mosquitoes,” he emphasised.

Final Objective

Afonso Moreira explained that the final objective is to assess whether this competition reduces the species' reproduction, since mating with sterile males does not produce offspring.

However, the researcher stressed that in this first phase the main objective is to understand the behaviour of the released specimens, especially their dispersal and survival capacity in the intervention area.

Regarding the second phase, Afonso Moreira said that it is scheduled for May of next year, “if the results of the first stage are favourable.”

We anticipate that, around that time, if everything goes well, we can conduct exactly this comparative study in which we release mosquitoes in one area and control them in another area. Then we try to understand if there is a difference in an area similar to the one where we are,” he explained.

Other successful experiences

According to the researcher, the technique has already been applied to other insects, namely the "fruit fly," and a similar initiative was developed in the Algarve.

Afonso Moreira stressed that the Lisbon project is focused on the Asian tiger mosquito, "due to its implications for public health."

The 'Aedes albopictus' can transmit diseases such as dengue, Zika, and yellow fever, and the risk arises if the mosquito bites an infected person and subsequently transmits the agent to another person.

Control measures

The official stressed that the release of sterile mosquitoes is only one of the control measures, defending the need to continue eliminating the places where this species reproduces, namely small accumulations of water, in public and private spaces.

Regarding the choice of Alvalade for the release of the mosquitoes, Afonso Moreira justified it with the characteristics of the parish, especially the vegetation and the courtyards, which can "provide favorable conditions for the development of the mosquito."

This project is supported and funded by the International Atomic Energy Agency and involves the collaboration of entities with experience in the production and release of sterile insects, including the Spanish company Tragsa.

It also involves the Francisco George Public Health Unit, the Directorate-General for Health, the National Institute of Health Dr. Ricardo Jorge (INSA), the Lisbon City Council and the Alvalade Parish Council.