This study provided an update on the epidemiology of T. vaginalis infection and showed the absence of the infection among MSM (0.0%) and a low prevalence among FSW (6.5%) in Togo. The overall prevalence of other STI were 16.8%, 9.3%, 7.5% and 7.2% for HIV, M. genitalium, C. Trachomatis and N. gonorrhoeae infections respectively. Among FSW population, risk factors associated with T. vaginalis infection were the geographic area (capital city, Lomé), lower age at first intercourse and infection with C. Trachomatis.
Our study reported that prevalence of T. vaginalis infection was 6.5% among FSW. In Rwanda, a descriptive cross-sectional study conducted in 2015 among 1,168 FSW reported a prevalence of 11.9% . In a 2-year longitudinal study conducted among 350 Kenyan FSW, baseline prevalence of T. vaginalis was 9.2% . In an another prospective cohort study among 352 South African youths including lesbian, gay, bisexual, transgender, and queer (LGBTQ), an overall prevalence of 4.8% has been reported (8.1% among female and 0.7% among male participants) . In a prospective, interventional cohort study of FSW aged 18 to 25 years in Ouagadougou among 321 HIV-uninfected FSW the prevalence of T. vaginalis was 3% . A prospective study among 302 pregnant women conducted in 2011 in Togo reported a prevalence of T. vaginalis of 3.7% . In a cross sectional study conducted in Mexico in 2011 among 105 FSW, the prevalence of T. vaginalis was 25.7%  which contrasts with that reported in FSWs in our study (6.5%). This difference could be explained by the methods used for the diagnosis of T. vaginalis, the age of the population and the associated risk factors.
Concerning associated risk factors among FSW, as observed in our study, C. trachomatis infection (adjusted Prevalence Ratio (aPR) = 8.53; 95%CI= [3.35–21.71]) was identified as a risk factor of T. vaginalis infection in Kenya . Also, in the same study, a significant association was reported between positive HIV status and T. vaginalis infection (aPR = 3.01; 95% CI= [1.45–6.24]). In South Africa, factors associated with T. vaginalis infection were marital status (not married) (OR 2.4; p < 0.001) and HIV positive infection (OR 1.6; p = 0.041) . These results contrast with that reported in our study.
Early age at first intercourse was associated with positive T. vaginalis infection in our study. Similar results have been reported by other studies such as in India in 2006 (AOR = 2.09; 95%CI: 1.09–4.00) . Overall prevalence of T. vaginalis among sexually active women aged 15–30 years was 8.5% and 14.4% for women under fifteen years at first sex. Another study of a nationally representative sample of 9,844 respondents aged 18 to 26 years in the United States found a significantly higher risk of T. vaginalis infection among adolescents and young adults who were younger at the time of their first sexual intercourse .
Also consistent with our result, a cross-sectional study conducted in four cities in sub Saharan Africa (Kisumu, Kenya; Ndola, Zambia; Cotonou, Benin and Yaoundé, Cameroon) among a random sample of 8,000 adults (2,000 in each city), aged 15–49 years showed a prevalence of T. vaginalis respectively of 29.3% in Kisumu, 34.3% in Ndola, 3.2% in Cotonou and 17.6% in Yaoundé. Early sexual debut (before age 15) was a significantly risk factor associated with T. vaginalis infection in women in Ndola (Zambia) .
In our study, no T. vaginalis was detected in MSM, which is different from prevalence found in similar population in African countries: 2,1% reported in Côte d’Ivoire in 2008  and 9% in South Africa in 2018 . In the Netherlands in 2014, the overall prevalence of T. vaginalis infection among 1,204 heterosexual men and MSM was respectively 1.1% and 0.0% , nearing our results. Reasons of prevalence disparities between FSW and MSM are not clear and the hypotheses are not confirmed. One of the most likely hypotheses is that T. vaginalis probably does not develop in the rectum and is therefore not often present in MSM . A cross-sectional study conducted in rural South Africa among women in 2017 noted a prevalence of vaginal and rectal T. vaginalis of 20.0% and 1.2%, respectively .
There was a special attention on the fact that T. vaginalis is much low among FSW than women in the general population especially among pregnant women. A possible explanation could be the systematic use of treatment in case of genital infection for FSW. In Togo, in case of STI symptoms, syndromic approach which includes the use of azithromycin, ceftriaxone, doxycycline, metronidazole as first line treatment are systematically used in care centers. However, additional and comparative studies are needed to shed light on interventions or hypotheses that could explain it.
Most of studies on T. vaginalis in Africa are conducted in pregnant women and report high prevalence in this population. A nested case-control study in Kenya among pregnant women reported a T. vaginalis infection prevalence of 35.4% (n = 79) , while in Nigeria  and South Africa , the prevalence of T. vaginalis infection among pregnant women was 18.7% and 15.0%, respectively.
To our knowledge, this was the first study reporting prevalence of T. vaginalis infection and STI among MSM and FSW in Togo. Another strength of this study includes the use of a sensitive laboratory assay for the reliable detection of T. vaginalis infection and the relationship with HIV. Finally, our study which was the first assessing factors associated with T. vaginalis among FSW in Togo, also provided useful information in order to design specific interventions within these populations.
There were few limitations to this study including the lack of data on treatment use among study participants, which may have certainly impacted observed STI prevalence. Furthermore, the standardized questionnaire submitted to participants can be biased (memory bias and social desirability bias) by the fact that it was based on self-reporting and may not reflect the overall sexual activity. Additionally, due to the cross-sectional nature of this analysis, we are unable to analyze the causality and temporality of the associations between T. vaginalis infection and other factors. Finally, because T. vaginalis infection was null among MSM in the study, we were unable to assess the relationship of T. vaginalis infection and predictor variables among this population.