Mathematical modelling to assess the impact of a hypothetical vaccine on the dynamics of human onchocerciasis

Abstract

Human Onchocerciasis (River Blindness) is a neglected tropical disease with no cure. Over the years, its control and elimination had relied on Ivermectin mass drug administration. However, some public health experts and other researchers have pointed out that Onchocerciasis complete elimination may not be achievable or may required a very long time with Ivermectin drug alone. Hence, the need for more research into other alternative control strategies to assist public health authorities. The aim of this study is to construct a mathematical model to examine the influence of a hypothetical vaccine as an additional control measure for the elimination of human Onchocerciasis. We computed the disease reproductive number with and without vaccination campaign and further derived a reduction factor by which a vaccination campaign will reduce Onchocerciasis spread in a community. The proposed model disease-free equilibrium is shown to be stable when the controlled R_o < 1. An equation for the disease endemic condition was derived and the conditions for the existence of two endemic equilibria when R_o < 1 or a globally asymptotically unique equilibrium when R_o > 1 were established. Local sensitivity revealed that black fly removal rate is the most significant parameter for controlling human Onchocerciasis. To examine the evolution of the model sub-classes, numerical simulations were carried out.