Theoretical Modelling of Schistosomiasis Transmission Dynamics Under Combined Praziquantel and Snail Control Interventions in Northwest Nigeria

Mathematical modelling of schistosomiasis transmission dynamics under multi-component interventions provides a quantitative basis for evaluating the additive or synergistic value of combining praziquantel mass drug administration with intermediate host snail control. This doctoral study developed and parameterised a deterministic compartmental transmission model for Schistosoma haematobium in Northwest Nigeria, incorporating age-structured human infection dynamics, Bulinus snail population density, seasonal transmission forcing, and the effects of praziquantel and mollusciciding interventions. Model parameters were estimated using Markov Chain Monte Carlo Bayesian inference calibrated against longitudinal epidemiological and snail density data from Sokoto State collected over five years. Uncertainty and sensitivity analyses were conducted. The model projected that annual praziquantel mass drug administration alone at 65 percent coverage would require 22 years to reduce prevalence below the 1 percent elimination target. Combining praziquantel with niclosamide-based mollusciciding in peak transmission seasons reduced the projected time to elimination to 11 years. Sensitivity analysis identified snail population rebound rate as the most influential parameter governing combined intervention efficacy. Stochastic model extensions predicted a 23 percent probability of elimination within 15 years at 80 percent drug coverage combined with biannual mollusciciding. These theoretical projections provide quantitative justification for reintroduction of snail control as a complementary tool in Nigeria's schistosomiasis elimination strategy. Keywords: mathematical modelling, schistosomiasis transmission, praziquantel, snail control, Northwest Nigeria.