Epidemiology and transmission dynamics of Trichomonas vaginalis infection among Iranian women: A framework for targeted public health interventions.

Trichomonas vaginalis (TV) is the most common non-viral sexually transmitted infection worldwide, with a substantial burden in Iran. However, beyond its documented prevalence, the epidemiological dynamics of the infection remain poorly understood. To identify key drivers of infection transmission and inform targeted interventions, we aimed to estimate the force of infection (FOI) and the infection clearance rate (ICR) for TV in Iran. To do so, we modeled the infection transmission dynamics using a Susceptible-Infected-Susceptible (SIS) framework. The model parameters were fitted via differential evolution optimization, calibrated against TV prevalence data obtained from a recent meta-analysis of Iranian women. This meta-analysis included 108 study records, representing a total population of 200,728 women. At the national level, the estimated FOI for TV in Iran was 2.35% (95% CI: 2.22–3.26%) and the ICR was 4.44% (95% CI: 4.32–5.28%), reflecting an overall decreasing trend. Provincially, while Yazd and Mazandaran had indices far exceeding the national average, they were also experiencing a declining trend. Conversely, Isfahan, Chaharmahal and Bakhtiari, and Sistan and Baluchistan were the only provinces with an increasing trend, a finding underscored by their FOI being higher than their ICR. Rising trends were also noted in specific populations: asymptomatic individuals, non-condom users, pregnant women, and rural residents. Our findings reveal that the dynamics of TV in Iran exhibit characteristics of a backward bifurcation, wherein transmission is perpetuated by reinfection, asymptomatic carriage, and non-protective behaviors. To interrupt this cycle, control programs must implement a multifaceted strategy including high-sensitivity diagnostics, comprehensive partner management, systematic retesting, and targeted screening of high-risk groups.