Among the major vectors of human diseases, mosquitoes of the Aedes and Anopheles genera are among the most devastating. Urbanisation, globalisation, and climate change have accelerated their spread, along with outbreaks of new mosquito-borne diseases. With the absence of efficient drugs and vaccines, as well as the problems associated with insecticide-based mosquito control, such as resistance among mosquitoes, and health and environmental impacts, major efforts are required to develop new and complementary control techniques, including the Sterile Insect Technique (SIT), for major mosquito species.
The SIT is an important component of area-wide integrated pest management (AW-IPM) programmes for key insect vectors such as Aedes and Anopheles mosquito species. These programmes help suppress or, in some situations, eradicate existing vector populations, as well as prevent the establishment of new vector populations.
There are many aspects of the mosquito SIT package that require increased efficiency to meet the requirements of deployment at the operational level, namely: mass rearing, release technology, quality control, and monitoring. However, prior to the operational use of SIT against mosquito species, one critical area where important advances need to be made concerns the development of sexing systems, including, but not restricted to, genetic sexing strains because it is important to release only males since female mosquitoes are blood feeders and can transmit disease.
In this respect, the IAEA, in cooperation with the Food and Agriculture Organization of the United Nationshas now completed the coordinated research project (CRP), D44001, on Exploring genetic, molecular, mechanical and behavioural methods of sex separation in mosquitoes. This initiative involved 19 scientists from 12 countries and resulted in the following key achievements and findings:
- Aedes albopictus and Anopheles arabiensis genetic sexing strains were developed using irradiation and classical genetics-based approaches with an insecticide resistance gene as selectable marker.
- Aedes genetic sexing strains were developed using irradiation and classical genetics-based approaches with a visible marker for selection.
- Sex separation strategies were developed for several Anopheles and Aedes species using Y-linked fluorescent markers, female-specific lethality, sex ratio distortion, sex conversion or protandry-based approaches.
- A temperature sensitive lethal (tsl) mutation was isolated in Anopheles arabiensis which can now be used for the development of a tsl-based genetic sexing strain.
- A laser sex sorting machine prototype based on Aedes mosquito pupal size dimorphism was developed.
The research carried out through this CRP generated more than 100 scientific publications in peer-reviewed journals and numerous presentations in international and national scientific meetings. The final CRP results, comprising 17 articles, were published in a Special Issue of the peer-reviewed scientific journal Parasites & Vectors. The genetic sexing strains and sex separation tools developed in the context of this CRP need to be validated under mass rearing conditions and in small scale pilot trials prior to their use in operational, large scale SIT programmes for the population suppression of Aedes and Anopheles mosquito species.