Abstract
A discrete worm-load process for a population infected with parasitic infection is considered. It is assumed that initial infections facilitate new infections due to immunosuppression and then there is a limitation due to the immune response. Our model consists of a finite number of partial differential equations which have been used to derive an ordinary differential equation system in the first three cumulants. The deterministic model corresponding to the stochastic one has been derived and analyzed. Conditions on model parameters that ensure the existence of backward bifurcation have been found. The minimum effort required to eliminate the infection has been computed. The impact of neglecting human host's age structure has been studied and the results showed that ignoring age-structure underestimates the transmission threshold which in turn overestimates the minimum effort required to eliminate the infection. Also, the impact of considering a polygamous mating process of worms within the host has been studied and the analysis showed that, compared to the effect of immunosuppression, one can neglect the mating process. The parameter values used to carry out our simulations represent onchocerciasis. (C) 2020 International Association for Mathematics and Computers in Simulation (IMACS). Published by Elsevier B.V. All rights reserved.