Objectives To better understand the epidemiology of Trichomonas vaginalis infection, we investigated the association between T. vaginalis and demographic, clinical, microbiological and behavioural characteristics of patients presenting with genital discharges to a primary healthcare clinic in Johannesburg, South Africa.

Methods During six annual surveys (2007–2012), 1,218 male urethral discharge syndrome (MUDS) and 1,232 vaginal discharge syndrome (VDS) cases were consecutively recruited. Diagnostic methods included nucleic acid amplification (Neisseria gonorrhoeae, Chlamydia trachomatis, T. vaginalis, Mycoplasma genitalium), microscopy (bacterial vaginosis, Candida) and serology (Treponema pallidum, HSV-2, HIV). Chi-squared tests and logistic regression analyses were used to identify predictors of T. vaginalis infection.

Results T. vaginalis prevalence decreased from 2007 to 2012 (men, 13.4% to 4.8%, p < 0.001; women, 33.8% to 23.1%, p < 0.001). Overall, 74 (6.1%) men and 291 (23.6%) women were T. vaginalis positive, with the highest prevalence in those aged ≥ 40 years (men, 13.6%; women, 30.9%). T. vaginalis infection occurred more often in pregnant women (adjusted odds ratio, aOR, 2.67; 95% confidence intervals, CI, 1.29–5.54) and women with serological evidence of T. pallidum (aOR, 1.63; 95% CI 1.08–2.45) or HSV-2 infections (aOR 1.75; 95% CI 1.16–2.64). T vaginalis infection occurred less often in men with co-existent gonorrhoea (aOR 0.35, 95% CI, 0.21–0.57) and in women with either BV (aOR 0.60, 95% CI 0.44–0.82) or Candida morphotypes (OR 0.61, 95% CI 0.43–0.86).

Conclusions Although the prevalence of T. vaginalis infection decreased over time, it remains an important cause of genital discharge in South Africa, particularly in older patients and pregnant women.