Economic optimization of Wolbachia-infected Aedes aegypti releases to prevent to dengue

Dengue is a systemic viral infection spread most commonly by the mosquito Aedes aegypti. The virus infects approximately 390 million individuals a year worldwide. Currently, the only available vaccine, Dengvaxia, is only approved for individuals with a confirmed previous dengue infection, and vector control through conventional methods has proven inefficient and costly. Recently, there have been several novel vector control techniques proposed to prevent dengue outbreaks. One of the most promising relies on infection with the bacterium, Wolbachia. In Ae. aegypti, Wolbachia is a vertically transmitted chronic infection, reducing the fitness of infected mosquitoes and blocking their ability to transmit dengue. Additionally, cytoplasmic incompatibility enables super-Mendelian inheritance, allowing for Wolbachia to spread to fixation in vector populations. However, economically efficient release strategies–optimizing both the rate of insect releases and the sizing of rearing facility capacity–have not yet been well characterized. In this paper, we describe a simple, model-based framework for making these decisions based on stochastic dynamic programming techniques. Using this framework, we find that conditional on sufficiently high facility capacity, the efficient strategy is robustly characterized as releasing at maximal rates initially before rapidly tapering to full cessation. Using empirical values for the biological and economic parameters in the model, we subsequently find that the optimal facility capacity is inelastic with respect to the baseline carrying capacity of the vector population. These results provide lessons for optimizing Wolbachia-based Aedes aegypti control programs, and for thinking about the efficiency of other, self-sustaining biological interventions for vector control.