Objective The social context of poverty is consistently linked to Trichomonas vaginalis infection, yet few studies regarding T. vaginalis have been conducted exclusively among low-income individuals. We identified social determinants of health associated with prevalent T. vaginalis infection among homeless and unstably housed adult women.

Methods Between April and October of 2010, we conducted cross-sectional T. vaginalis screening and behavioural interviews in an existing cohort of San Francisco homeless and unstably housed women. Data were analysed using multivariable logistical regression.

Results Among 245 study participants, the median age was 47 years and 72% were of non-Caucasian race/ethnicity. T. vaginalis prevalence was 12%, compared to 3% in the general population, and 33% of infected individuals reported no gynaecological symptoms. In adjusted analysis, the odds of T. vaginalis infection were lower among persons older than 47 years, the population median (OR=0.14, 95% CI 0.04 to 0.38), and higher among those reporting recent short-term homeless shelter stays (OR=5.36, 95% CI 1.57 to 18.26). Race and income did not reach levels of significance. Sensitivity analyses indicated that testing all women who report recent unprotected sex would identify more infections than testing those who report gynaecological symptoms (20/30 vs 10/30; p=0.01).

Conclusions The prevalence of T. vaginalis is high among homeless and unstably housed adult women, over one-third of infected individuals have no gynaecological symptoms, and correlates of infection differ from those reported in the general population. Targeted screening and treatment among impoverished women reporting recent unprotected sex, particularly young impoverished women and all women experiencing short-term homelessness, may reduce complications related to this treatable infection.