Thousands of male Aedes aegypti mosquitoes carrying the Wolbachia bacterium will be released regularly into three former dengue clusters at Tampines Avenue 4, Yishun Street 21, as well as Jalan Riang and Jalan Sukachita in Serangoon over six months from October 2016, the National Environment Agency (NEA) announced on Saturday (Aug 27). It is part of a “small-scale” field study and comes after a comprehensive risk assessment found it would be safe to release such mosquitoes, with no risk to human health and insignificant impact on ecology, NEA said.
STOPPING THE CYCLE
Only female Aedes mosquitoes spread dengue by biting humans. Should a male carrier of the Wolbachia bacterium mate 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.
NEA said it carried out a four-year evaluation of the process, involving critical reviews of existing research, consultations with various stakeholders such as academic experts, medical and healthcare professionals, and non-governmental organisations such as nature groups. It found the bacterium – which is naturally found in insects in the wild – to offer suitable biological properties
The field study will observe how far the mosquitoes are able to disperse outside the lab, as well as how high they can fly. It will also gauge their lifespans in the wild, and how well they can compete for mates. An average of one to three mosquitoes per resident will be released regularly in areas such as stairwells, void decks, open spaces between blocks of high-rise homes, and outside landed homes of the three estates. NEA stated that mosquitoes will not be released directly into homes.
The three estates represent a cross-section of typical housing estates in Singapore, and provide a good baseline from which to make comparative studies.
The findings will support the design of another field suppression trial to be held over one to two years in 2017, to test if the technology is effective in bringing down mosquito populations – and by extension, possibly impacting the spread of dengue. If the tests are successful, NEA could roll-out this method to fight dengue in high-risk areas from 2019.