A THEORETICAL STUDY ON SCHISTOSOMIASIS INFECTION MODEL: APPLICATION OF BIOLOGICAL OPTIMAL CONTROL

A general mathematical model for schistosomiasis is formulated that incorporates the miracidia and cercariae dynamics, since parasites play an important role in the transmission dynamics of schistosomiasis. This model is an extension of the study undertaken in Diaby etc [6] concerning the evolution of a schistosomiasis infection. Meanwhile, optimal control theory is applied to the proposed model. In the first part of our analysis we describe and propose a complete mathematical analysis of a new mathematical model for schistosomiasis infection with fixed control for both drug and biological treatment. It also includes a net inflow of competitor snails into the aquatic region at the rate $ u $ per unit of time as control term. Schistosomiasis is associated with water resource development such as dams and irrigation schemes, where the snail is the intermediate host of the parasite breeds. The snail intermediate host breeds in slow-flowing or stagnant water. We establish a deterministic model to explore the role of biological control strategy. We derive the basic reproduction number $ \mathcal{R}_0 $ and establish that the global dynamics are completely determined by the values of $ \mathcal{R}_0 $. It is shown that the disease can be eradicated when $ \mathcal{R}_0 \leq 1 $. In the case where $ \mathcal{R}_0 >1 $, we prove the existence, uniqueness and global asymptotic stability of an endemic equilibrium. We also show how the control $ u $ can be chosen in order to eradicate the disease. In the second part, we take the controls as time dependent and obtain the optimal control strategy to minimize both infected humans and snails populations. All the analytical results are verified by simulation works. Some important conclusions are given at the end of the paper.