Mathematical Modeling and Analysis of Trachoma Transmission Dynamics: Evaluating the Synergy of Mass Drug Administration and Adult-Targeted Education

Trachoma remains a leading cause of preventable blindness in many low-resource settings, driven by persistent transmission within closely interacting age groups. In this study, we develop and analyze a nonlinear age-structured compartmental model that captures the transmission dynamics of trachoma between children and adults. The model incorporates cross-age infection pathways, demographic processes, and Holling Type-II saturated incidence to reflect behavioral and environmental limitations on disease spread. We establish fundamental qualitative properties of the model, including positivity, boundedness, and well-posedness of solutions. Using the next-generation matrix approach, the basic reproduction number R0 is derived and shown to govern the global dynamics of the system. Specifically, the disease-free equilibrium is globally asymptotically stable when R0 1. Furthermore, bifurcation analysis reveals the presence of a forward (transcritical) bifurcation at R0=1, indicating that disease elimination can be achieved through effective threshold reduction strategies. A comprehensive sensitivity analysis, based on Latin Hypercube Sampling and Partial Rank Correlation Coefficients (LHS-PRCC), identifies transmission parameters—particularly child-to-child and adult-to-child contact rates—as the most influential drivers of disease spread, whereas recovery and mortality parameters play a significant mitigating role. Numerical simulations are conducted to evaluate the impact of intervention strategies. Results demonstrate that biannual mass drug administration (MDA) targeting children substantially reduces short-term prevalence but fails to prevent long-term resurgence when implemented in isolation. In contrast, adult-targeted hygiene education reduces transmission intensity and lowers endemic levels. A combined intervention strategy yields a strong synergistic effect, significantly accelerating disease suppression and reducing long-term prevalence. Taken together, the findings highlight the critical role of integrated control strategies that combine medical treatment with behavioral interventions. In particular, targeting adult-mediated transmission pathways is essential for sustainable trachoma elimination and aligns with the WHO SAFE strategy.