  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.
