Genetic Modification of Mosquito Populations to Make Them Incapable of Transmitting Dengue Virus

In this proposal we develop an iWlovative approach to genetically modifying mosquito populations to make them incapable of transmitting dengue virus. This approach targets insect age, one of the most sensitive parameters influencing the epidemiology of insect-transmitted diseases. By introducing known life-shortening strains ()f inherited Wolbachia endosymbionts into mosquitoes we can selectively eliminate old mosquito adults in the population. Because of the length of the extrinsic incubation period of dengue virus within a mosquito, the removal of old individuals can stop disease transmission to humans. Moreover, the inherited Wolbachia endosymbionts that are capable of shortening Hfcspan provide their own genetic drive mechanjsm that allows them to spread throughout the host population. This mechanism, cytoplasmic incompatibiJity, has been well characterized in the laboratory and the field. Finally this approach has the potential to be developed without the need for transgenic insects being rcleeed into the environment and is thU~i likely to be seen as an acceptable intervention strategy by affected communities. Theoretical modelling with realistic parameter estimates indicates that this strategy may be able to reduce dengue transmission by 90-100% in a given region. We will achieve this goal by completing 4 major objectives as fonows: Objective 1: We will generate strains of mosquitoes carrying life-shortening Wolbachia strains and determine the molecular mode of action of the life shortening phenotype. Objective 2: We will characterize laboratory populations of mosquito strains developed in Objective 1 with regard to the degree of life shortening they display and the ability of the introduced Wolbachia 10 drive itself into laboratory populations. Objective 3: We will develop baseline data on our target mosquito species at three field sites. We will characterize population age structure and other relevant ec:ological characteristics. We will also test the efficacy of the approach at one location in large field cages. Objective 4: We will fonn partnerships with communities and regulatory and government agencies in three countries in order to evaluate impediments to the use of this strategy and to put in place a framework for future implementation. In order to achieve our objectives we have brought together an inu:mational team of scientists witb expertise covering Wolbachia genetics, Aedes biology and ecology, dengue transmission and control, and health education and promotion. These scientists are based in a number of countries including Australia, Japan, Thailand, Vietnam and the USA. A large amount of the proposed work will be undertaken within disease endemic countries. We will focus this combined expertise to solve the major issues relating to the development and deployment of this strategy, from the molecular aspects of insect life-shortening through to tbe social and community based aspects of future implementation of this strategy. Fieldwork will be undertaken in three countries, Australia, Thailand and Vietnam. These three dengue transmission areas represent a range of different ecological and cultural environments. The successful completion of these aims will set the stage for the implementation phase of this strategy. Upon completion of the major objectives in this proposal we will have produced: strains of mosquitoes that contain life-shortening Wolbachia, data to detennine the best strategy for release and spread of these strains, an understanding of tb.e predicted efficacy of the approach, and methods to direct1y measure efficacy in the fie1d. The second implementation phase is considered outside the scope of this jnitial five-yc~ grant period but we expect to be ready to deploy this strategy at the end of the five-year grllDting period. A feature of our proposal is the ability to leverage foundation funding. We have already obtained an agreement for additiona1 matching funding of AUDS 1,000,000 as described in the research plan and believe that other opportunities with agencies in A