SINGAPORE: The first phase of a study on mosquitoes carrying the Wolbachia bacteria has been completed, with the successful suppression of 50 per cent of the targeted Aedes aegypti population, the National Environment Agency (NEA) said on Friday (Dec 8).
Since October 2016, male Wolbachia-carrying Aedes aegypti mosquitoes have been released on a regular basis at three selected sites at Braddell Heights, Nee Soon East and Tampines West. This is to understand their behaviour and ecology, and see if they can suppress the population of urban Aedes aegypti mosquitoes.
Since only female Aedes mosquitoes spread dengue by biting humans, if a male carrier of the Wolbachia bacterium mates with an uninfected female mosquito, the resulting eggs will not hatch.
NEA hopes that by releasing sufficient numbers of Wolbachia-carrying Aedes aegypti males, they can compete successfully against wild males and eventually drive down mosquito numbers as the population fails to reproduce.
Over time, this could also reduce the potential spread of dengue. NEA expects that the method could also help prevent the transmission of other mosquito-transmitted diseases such as Chikungunya and Zika.
Phase 1 of the study has met its objectives and a second recommended phase will commence in the second quarter of next year, NEA said.
The study reported that much fewer Aedes aegypti adult mosquitoes were found at sites where the male Wolbachia-Aedes mosquitoes were released, implying that the method is effective.
At the same time, half of the collected Aedes mosquito eggs did not hatch at the released sites, which provided strong indication that the released Wolbachia-Aedes males had successfully competed with the urban Aedes males and mated with some of the urban Aedes aegypti females.
HIGH-RISE URBAN LANDSCAPE POSES CHALLENGES
The field study also revealed two ecological challenges that are unique to Singapore’s high-density and high-rise urban landscape, and should be addressed to increase the impact of the suppression, the NEA said.
Firstly, the report noted how Aedes aegypti mosquitoes were able to move easily from surrounding areas into the release sites, thus reducing the suppression effect of Wolbachia-Aedes.
Secondly, it was noted that there is a high density of Aedes aegypti mosquitoes on higher floors, where not enough Wolbachia-Aedes mosquitoes can reach.
Data collected on how high and far the male Wolbachia-carrying Aedes aegypti (Wolbachia-Aedes) mosquitoes can fly, how long they live and their mating competitiveness in actual field conditions, will contribute to future field studies.
The Wolbachia technology, if proven effective, will further strengthen our capabilities to tackle dengue and other mosquito-borne diseases, the agency added.
"This is especially crucial as higher global temperatures resulting from climate change can have an impact on the spread of mosquito-borne diseases and public health," NEA said.