MODELING the INFECTION DYNAMICS of ONCHOCERCIASIS and ITS TREATMENT

Onchocerciasis is one of the neglected tropical diseases caused by Onchocerca volvulus. Ivermectin is known to be effective in the treatment of onchocerciasis because it suppresses the production of microfilariae by the adult female worms for a few months following treatment thus reducing transmission. In this study, a deterministic model is developed to assess the effect of mass treatment of onchocerciasis with ivermectin. The basic reproduction number, R0, of the model system is determined and it is observed that the model exhibits backward bifurcation for some parameters implying the existence of multiple endemic equilibria when R0 < 1. The existence of multiple equilibria emphasizes the fact that R0 < 1 is not sufficient to eradicate the disease and the need is to lower R0 much below one to make the disease-free equilibrium globally stable. Numerical simulations are done and conclusions drawn with respect to the known treatment protocols in endemic areas. The study results suggest that the mass treatment of the disease with ivermectin should cover a higher proportion of the population to control the disease and eventually eliminate it from the population.