Periodic Reporting for period 4 - REVOLINC (Revolutionizing Insect Control)
Período documentado: 2021-03-01 hasta 2021-08-31
According to the World Health Organization (WHO), vector-borne diseases account for 17% of infectious diseases and cause more than one million deaths each year. These include, in order of importance, malaria transmitted by Anopheles mosquitoes and arboviruses transmitted by Aedes mosquitoes like dengue, chikungunya, yellow fever and Zika. Awareness of the toxicity of insecticides to living organisms and ecosystems is leading a growing number of countries to reduce the number of approved molecules. Moreover, resistance to pyrethroids, the most widely used class of insecticides against insects, is spreading, which could lead to their discontinuation in the short-term. Many countries are thus looking for alternative vector control methods against mosquitoes including genetic control, which shows promise.
The REVOLINC project (ERC Consolidator grant no. 682387) aimed at developing environmentally-friendly alternatives to fight insects invasions through the development of innovant technologies to control three types of pest insects (mosquitoes, tse-tse flies and Mediterranean fruit flies), in particular Aedes aegypti and Aedes albopictus (major vectors of arboviruses), Ceratitis capitata (a major pest for agriculture) and Glossina palpalis gambiensis (a major vector of trypanosomes in Africa). We wanted to improve the “sterile insect technique” (SIT) which consists in mass rearing male insects, sterilizing them by radiation and releasing them into the environment, where they compete with their wild non-sterile counterparts to reproduce. The objective is to reduce the fertility of the overall population and eventually cause its collapse. The “boosted sterile insect technique” (boosted SIT) involves sterile males contaminated with a biopesticide passing it on to females and killing them or their progeny.
The REVOLINC project (ERC Consolidator grant no. 682387) aimed at developing environmentally-friendly alternatives to fight insects invasions through the development of innovant technologies to control three types of pest insects (mosquitoes, tse-tse flies and Mediterranean fruit flies), in particular Aedes aegypti and Aedes albopictus (major vectors of arboviruses), Ceratitis capitata (a major pest for agriculture) and Glossina palpalis gambiensis (a major vector of trypanosomes in Africa). We wanted to improve the “sterile insect technique” (SIT) which consists in mass rearing male insects, sterilizing them by radiation and releasing them into the environment, where they compete with their wild non-sterile counterparts to reproduce. The objective is to reduce the fertility of the overall population and eventually cause its collapse. The “boosted sterile insect technique” (boosted SIT) involves sterile males contaminated with a biopesticide passing it on to females and killing them or their progeny.
In the first part of the project, a contamination technique was developed to coat sterile male insects with biocide or biopesticide formulations in order to achieve the desired effect of transfer to females without reducing their survival/ quality. This technique is based on impregnating chilled insects with a powder formulation.
We then tested several formulations of pyriproxifen, strains of Densovirus and entomopathogenic fungi in the laboratory and in semi-field trials before selecting the best candidates for the field trials. Based on the laboratory results, models predicted that boosted SIT could reduce the number of sterile males required to reduce Aedes vector populations and control dengue epidemics by more than 95% compared to SIT. More complex models integrating a spatial component and meteorological data were developed to compare the efficiency of this control method with other methods in temperate and tropical climates.
We also optimized all mass-rearing and irradiation protocols for Aedes mosquitoes, and tested an aerial drone-release system in the field, allowing homogeneous releases of sterile male mosquitoes without reducing their quality. The release system has been patented worldwide and validated in the field in both rural and urban settings.
Genetic sexing systems based on fluorescent markers inserted into the sexual loci of Aedes mosquitoes have been developed. They allow sorting female from males at the L1 stage in both Ae. albopictus and Ae. aegypti. We investigated the potential of these strains as an operational sexing tool using a COPAS sorter at a small scale. Two sexing options were proposed, one based on the release of fluorescent transgenic males and the other of non transgenic males, using a crossbreeding scheme.
We have participated in several expert groups to implement risk analyses on genetic control of mosquitoes, including SIT, and have obtained all the authorisations to run pilot field trials of boosted SIT against Aedes albopictus and Ceratitis capitata (medflies) in the Valencia region, Spain, and against Aedes aegypti in Reunion island, France. The strategy was also transferred to an elimination project targeting Glossina palpalis gambiensis (tsetse) in the Dakar region of Senegal. All of these trials were successful in reducing target populations and the results are still being analysed.
Finally, an acceptability study has been conducted with the aim of reflecting, beyond the mere need for cutting edge research and development, the deep interweaving of technology, science and society.
The results were presented at 10 international conferences and 5 press releases were conducted.
We then tested several formulations of pyriproxifen, strains of Densovirus and entomopathogenic fungi in the laboratory and in semi-field trials before selecting the best candidates for the field trials. Based on the laboratory results, models predicted that boosted SIT could reduce the number of sterile males required to reduce Aedes vector populations and control dengue epidemics by more than 95% compared to SIT. More complex models integrating a spatial component and meteorological data were developed to compare the efficiency of this control method with other methods in temperate and tropical climates.
We also optimized all mass-rearing and irradiation protocols for Aedes mosquitoes, and tested an aerial drone-release system in the field, allowing homogeneous releases of sterile male mosquitoes without reducing their quality. The release system has been patented worldwide and validated in the field in both rural and urban settings.
Genetic sexing systems based on fluorescent markers inserted into the sexual loci of Aedes mosquitoes have been developed. They allow sorting female from males at the L1 stage in both Ae. albopictus and Ae. aegypti. We investigated the potential of these strains as an operational sexing tool using a COPAS sorter at a small scale. Two sexing options were proposed, one based on the release of fluorescent transgenic males and the other of non transgenic males, using a crossbreeding scheme.
We have participated in several expert groups to implement risk analyses on genetic control of mosquitoes, including SIT, and have obtained all the authorisations to run pilot field trials of boosted SIT against Aedes albopictus and Ceratitis capitata (medflies) in the Valencia region, Spain, and against Aedes aegypti in Reunion island, France. The strategy was also transferred to an elimination project targeting Glossina palpalis gambiensis (tsetse) in the Dakar region of Senegal. All of these trials were successful in reducing target populations and the results are still being analysed.
Finally, an acceptability study has been conducted with the aim of reflecting, beyond the mere need for cutting edge research and development, the deep interweaving of technology, science and society.
The results were presented at 10 international conferences and 5 press releases were conducted.
The project developed techniques for contaminating sterile males with biopesticides, as well as a new alginate formulation to maximize the transfer of biocides between insects and to their breeding sites. Based on the quantification of their impact on contaminated females and their fertility & fecundity under laboratory conditions, models demonstrated that boosted SIT could be a game changer in the control of mosquito-borne diseases. At the same time, the full SIT package, including mass-rearing, sterilization, sex-sorting, quality-control and drone release has been optimized for implementation in pilot field trials. These field trials were successfully conducted against all target species and resulted in a significant reduction in their densities. We have also developed Genetic Sexing Strains that could allow a huge upscaling in genetic programs against mosquitoes, as well as a significant reduction of the female contamination rate thus reducing the biting nuisance in mass rearing facilities and the vector risk related to the release of females in the field.