Evaluating the Usefulness of Paratransgenesis for Malaria Control

Malaria is a serious global health problem which is especially devastating to the developing world. Mosquitoes are the carriers of the parasite responsible for the disease, and hence malaria control programs focus on controlling mosquito populations. This is done primarily through the spraying of insecticides, or through the use of insecticide treated bed nets. However, usage of these insecticides exerts massive selection pressure on mosquitoes, resulting in insecticide resistant mosquito breeds. Hence, developing alternative strategies is crucial for sustainable malaria control. Here we explore the usefulness of paratransgenesis, i.e., introducing genetically engineered bacteria which secrete anti-plasmodium molecules, inside the mosquito midgut. The bacteria enter a mosquito's midgut when it drinks from a sugar bait, i.e., a sugar solution containing the bacterium. We formulate a mathematical model for evaluating the number of such baits required for preventing an outbreak. We study scenarios where vectors and hosts mix homogeneously as well as heterogeneously. We perform a full stability analysis and calculate the basic reproductive number for both the cases. Additionally, for the heterogeneous mixing scenario, we propose a targeted bait distribution strategy. The optimal bait allocation is calculated and is found to be extremely efficient in terms of bait usage. Our analyses suggest that paratransgenesis can prevent an outbreak, and hence it offers a viable and sustainable path to malaria control.