Impact of Screening and Contact Tracing on a Deterministic Compartmental Model for Chlamydia Transmission Dynamics

Abstract Chlamydia trachomatis remains the most prevalent bacterial sexually transmitted infection worldwide, with over 128 million new cases reported annually. Despite the availability of effective treatment, its largely asymptomatic nature and high reinfection rates continue to sustain transmission, posing a major public health concern. In this study, a seven-compartment deterministic model is developed to investigate the transmission dynamics of Chlamydia trachomatis. The model incorporates key epidemiological features, including screening detection with reduced infectiousness, partial waning immunity, and realistic treatment pathways. Using the next-generation matrix method, the basic reproduction number is derived, confirming the potential for endemic persistence under baseline parameter values. Stability analysis shows that the disease-free equilibrium is locally asymptotically stable when the reproduction number is less than one and unstable otherwise. Furthermore, the endemic equilibrium is proven to be globally asymptotically stable under certain conditions using Lyapunov methods, with the possibility of backward bifurcation indicating that reducing the reproduction number below unity may not be sufficient for disease elimination. Normalized sensitivity analysis identifies condom efficacy as the most influential parameter in reducing transmission, followed by treatment success rate, duration of immunity, and symptomatic care-seeking behavior. In contrast, transmission probability and infectiousness during screening exert strong positive effects on disease spread, while disease-induced mortality parameters have minimal impact on overall dynamics. The model highlights the critical role of the large asymptomatic population in sustaining transmission and demonstrates that rapid waning of immunity, approximately 180 days, contributes significantly to high reinfection rates. The findings emphasize that effective control of Chlamydia trachomatis requires integrated intervention strategies. These include sustained condom promotion, expansion of targeted screening programs, minimization of diagnostic delays, and efficient partner notification systems. Additionally, repeat testing protocols are essential to address reinfection driven by short-lived immunity. Keywords: Chlamydia trachomatis, Transmission dynamics, Basic reproduction number, Sensitivity analysis, Simulations