Syphilis is a sexually transmitted disease (STD) due to
A number of studies around the world have reported high prevalence of syphilis among risk groups including female sex workers (FSW) [
We conducted a cross-sectional survey between February 2013 and May 2014 among FSW in five cities in Burkina Faso. Participants were recruited using respondent-driven sampling (RDS) to be part of HIV seroprevalence and behavioral studies. RDS is an approach to recruit hidden and hard-to-reach populations [
The study was conducted in five cities of Burkina Faso: Ouagadougou (the capital city in the centre), Bobo-Dioulasso (in the Hauts-Bassins region), Koudougou (in the middle west), Ouahigouya (in the north), and Tenkodogo (in the middle east). These areas were selected based on the urbanization level, the prevalence of HIV, and the geographical location.
Inclusion criteria were aged ≥ 18 years, assigned female sex at birth, earned at least 50% of her income in the last 12 months from sex work, lived in the selected city during the last three months, and provided informed consent. Recruitment methods were fully described elsewhere [
The sample size was based on expected HIV prevalence and calculated to recruit 345 FSW in the two major cities of Ouagadougou and Bobo-Dioulasso and 126 FSW in the other medium cities of Koudougou, Ouahigouya, and Tenkodogo. To calculate the sample size, we hypothesized that populations who use condoms would have 75% lower HIV prevalence than that of those not using condoms, assuming condom efficacy as 80% (73% to be cautious). A design effect of 1.5 was used associated with the RDS methods; we set 0.05 for type I errors and 80% power.
Data were collected from February to August 2013 in Ouagadougou and Bobo-Dioulasso and from February to May 2014 in Koudougou, Ouahigouya, and Tenkodogo. Upon informed consent and completion of a behavioral questionnaire, participants received counseling for HIV and syphilis screening. Participant information was anonymized and identified with a unique code number to protect confidentiality. Data collected in the questionnaire included demographic and socioeconomic information, the number of sexual partners, sexual behavior (including condom use), HIV-related knowledge, and STD screening and symptoms. In each city, one site was used for data collection. The team was trained on the study procedures and on health research ethics prior to the onset of the survey. The staff included one site manager, one coupon manager, two data collectors for questionnaire administration, a nurse for HIV and syphilis pre- and posttest counseling, and a lab technician for blood collection and sample processing for HIV and syphilis screening. Participants with positive syphilis test results were treated in situ while those with positive HIV test results were referred to dedicated staff for appropriate care.
Figure
Flowchart of syphilis screening among study participants.
Data were double entered into EpiData 3.1 (the EpiData Association, Odense, Denmark) software and analysed with Stata 14 (StataCorp, College Station, TX). RDS-weighted analysis was only used to estimate active syphilis and syphilis serological markers seroprevalence for each city. To have sufficient number of positive cases of syphilis serological markers for statistical analysis, data from all study cities were pooled. The pooled data were not analyzed using RDS weighting because there was no overlap in recruitment between study cities. Baseline survey data and biological test results of participants were summarised with descriptive statistics. Bivariate and multivariate logistic regression analyses were conducted to identify factors associated with syphilis serological markers. Associations were expressed as odds ratios (ORs) and adjusted odds ratios (aORs) with 95% confidence intervals (CIs). Results significant at the
The National Ethics Committee for Health Research in Burkina Faso reviewed and approved the study protocol prior to participant recruitment. Collected data were anonymized with a unique identifier code so that no participant could be identified by their name. All FSW detected with positive antibodies were treated in situ with one intramuscular dose of benzathine benzylpenicillin G 2.4 MUI and kept under observation over 30 minutes to capture any immediate adverse event. Positive cases presenting allergy received doxycycline 100 mg tablet over 2 weeks. FSW were sensitized on safe sex (protection measures against STDs), were encouraged to undergo a serological test for syphilis every 3 to 6 months, and were provided with condoms and lubricants free of charge.
A total of 1045 FSW were screened for syphilis in the five study cities: 349 FSW in Ouagadougou, 350 in Bobo-Dioulasso, 115 in Koudougou, 102 in Ouahigouya, and 129 in Tenkodogo. Approximately 44.7% (463/1036) of those interviewed self-reported a history of STD-related symptoms during the last twelve months prior to the survey. Only 1.3% (14/1042) underwent syphilis serological testing during the last twelve months.
The mean age of the study population was 27.2 ± 0.2 years; 59.8% (95% CI: 56.8–62.7) were single and 67.8% (95% CI: 64.9–70.6) came from Burkina Faso. Approximately 31.1% (95% CI: 28.4–34.0) of FSW had no formal education while more than 36% (95% CI: 33.3–39.2) had a primary school education. Unemployment outside of sex work was common among FSW, 58% (95% CI: 54.9–60.9). Only 4.7% (95% CI: 3.6–6.2) were students. The proportion of FSW who were divorced, widowed, or separated was 30.4% (95% CI: 27.7–33.3); more than 70% of the participants were mothers (Table
Characteristics of female sex workers in Burkina Faso.
Characteristics | Number ( |
Proportion (%) | 95% CI |
---|---|---|---|
|
|||
18-19 | 118 | 11.3 | 9.5–13.4 |
20–24 | 364 | 34.8 | 32.0–37.8 |
25–29 | 245 | 23.4 | 21.0–26.1 |
≥30 | 318 | 30.4 | 27.7–33.3 |
|
|||
None | 324 | 31.1 | 28.4–34.0 |
Primary | 377 | 36.2 | 33.3–39.2 |
Secondary | 340 | 32.7 | 29.9–35.6 |
|
|||
Student | 49 | 4.7 | 3.6–6.2 |
Worker | 390 | 37.4 | 34.5–40.4 |
Unemployed | 604 | 57.9 | 54.9–60.9 |
|
|||
Single | 625 | 59.8 | 56.8–62.7 |
Married or cohabitating | 102 | 9.8 | 8.1–11.7 |
Divorced/separated/widowed | 318 | 30.4 | 27.7–33.3 |
|
|||
0 | 277 | 26.5 | 23.9–29.3 |
1 | 397 | 38.0 | 35.1–41.0 |
2+ | 371 | 35.5 | 32.7–38.4 |
|
|||
<1 year | 237 | 23.0 | 20.5–25.7 |
1–5 years | 506 | 49.2 | 46.1–52.2 |
6+ years | 286 | 27.8 | 25.1–30.6 |
|
|||
1–14 | 451 | 45.9 | 42.8–49.1 |
15–21 | 241 | 24.5 | 21.9–27.3 |
22–28 | 71 | 7.2 | 05.7–09.0 |
29–80 | 219 | 22.3 | 19.8–25.0 |
|
|||
No | 188 | 18.0 | 15.8–20.5 |
Yes | 856 | 82.0 | 79.5–84.2 |
|
|||
No | 403 | 39.5 | 36.5–42.5 |
Yes | 618 | 605. | 57.5–63.5 |
|
|||
No | 573 | 55.3 | 52.1–58.1 |
Yes | 463 | 44.7 | 41.5–47.6 |
|
|||
No | 829 | 79.6 | 77.0–81.9 |
Yes | 213 | 20.4 | 18.1–23.0 |
|
|||
Positive | 168 | 16.1 | 13.9–18.4 |
Negative | 877 | 83.9 | 81.7–86.0 |
|
|||
Positive | 59 | 5.6 | 4.4–7.2 |
Negative | 986 | 94.4 | 92.8–95.6 |
|
|||
Positive | 15 | 1.4 | 0.9–2.4 |
Negative | 1030 | 98.6 | 97.6–99.1 |
|
|||
Ouagadougou | 349 | 33.4 | 30.6–36.3 |
Bobo-Dioulasso | 350 | 33.5 | 30.9–36.4 |
Koudougou | 115 | 11.0 | 9.2–13.0 |
Ouahigouya | 102 | 9.8 | 8.1–11.7 |
Tenkodogo | 129 | 12.3 | 10.5–14.5 |
|
|||
Burkina Faso | 709 | 67.8 | 64.9–70.6 |
Other countries | 336 | 32.2 | 29.4–35.0 |
|
1045 | 100.0 |
STD = sexually transmitted disease; CI = confidence interval.
The prevalence of syphilis serological markers was 5.6% (95% CI: 4.4–7.2) among FSW overall, and active syphilis was found among 1.4% (95% CI: 0.9–2.4) of the participants. RDS weighted prevalence of syphilis serological markers and active syphilis by city were, respectively, estimated between 0.0% and 11.0% (95% CI: 8.1–14.7) and 0.0% and 2.2% (95% CI: 1.1–4.4) (Table
Active syphilis and syphilis serological markers prevalence among female sex workers by city.
Variables | All cities ( |
Ouagadougou ( |
Bobo-Dioulasso ( |
Koudougou ( |
Ouahigouya ( |
Tenkodogo ( |
|||||
---|---|---|---|---|---|---|---|---|---|---|---|
|
Unadjusted % | RDS-adjusted % (95% CI) | Unadjusted % | RDS-adjusted % (95% CI) | Unadjusted % | RDS-adjusted % (95% CI) | Unadjusted % | RDS-adjusted % (95% CI) | Unadjusted % | RDS-adjusted % (95% CI) | |
Syphilis serological markers |
|
4.3 | 4.4 (2.7–7.2) |
|
11.0 (8.1–14.7) |
|
1.7 (0.4–6.6) |
|
— |
|
1.5 (4.4–7.2) |
Active syphilis |
|
1.4 | 1.4 (0.6–3.3) |
|
2.2 (1.1–4.4) |
|
1.7 (0.4–6.6) |
|
— |
|
— |
Prevalence of syphilis serological markers and of active syphilis among female sex workers in Burkina Faso.
FSW characteristics |
|
Syphilis serological markers (%) |
|
Active syphilis (%) |
|
---|---|---|---|---|---|
|
|||||
18-19 | 118 | 3.4 | 0.025 |
0.0 | 0.558 |
20–24 | 364 | 3.8 | 1.6 | ||
25–29 | 245 | 5.3 | 1.2 | ||
≥30 | 318 | 8.8 | 1.9 | ||
|
|
|
|
||
|
|||||
None | 324 | 9.3 | <0.001 |
2.8 | 0.037 |
Primary | 377 | 5.4 | 0.8 | ||
Secondary | 340 | 2.1 | 0.6 | ||
|
|||||
Student | 49 | 8.2 | 0.216 | 2.0 | 0.723 |
Worker | 390 | 4.2 | 1.3 | ||
Unemployed | 604 | 5.7 | 1.5 | ||
|
|||||
Single | 625 | 4.5 | 0.133 | 0.8 | 0.038 |
Married or cohabitating | 102 | 6.9 | 1.0 | ||
Divorced/separated/widowed | 318 | 7.5 | 2.8 | ||
|
|||||
0 | 277 | 26.5 | 0.005 | 0.36 | 0.162 |
1 | 397 | 38.0 | 1.52 | ||
2+ | 371 | 35.5 | 2.16 | ||
|
|||||
<1 year | 237 | 2.5 | 0.005 |
0.4 | 0.169 |
1–5 years | 506 | 5.3 | 1.4 | ||
6+ years | 286 | 9.1 | 2.5 | ||
|
|||||
1–14 | 451 | 3.5 | 0.001 |
0.9 | 0.014 |
15–21 | 241 | 4.6 | 0.4 | ||
22–28 | 71 | 9.9 | 2.8 | ||
29–80 | 219 | 11.0 | 3.7 | ||
|
|||||
No | 188 | 1.6 | 0.008 |
0.5 | 0.494 |
Yes | 856 | 6.5 | 1.6 | ||
|
|||||
No | 403 | 6.9 | 0.124 | 1.2 | 0.418 |
Yes | 618 | 5.0 | 1.6 | ||
|
|||||
No | 573 | 5.2 | 0.876 | 1.6 | 0.806 |
Yes | 463 | 6.3 | 1.3 | ||
|
|||||
No | 829 | 6.1 | 0.177 | 1.8 | 0.051 |
Yes | 213 | 3.8 | 0.0 | ||
|
|||||
Positive | 168 | 7.1 | 0.359 | 0.6 | 0.488 |
Negative | 877 | 5.4 | 1.6 | ||
|
|||||
Burkina Faso | 709 | 5.9 | 0.572 | 1.4 | 1.000 |
Other countries | 336 | 5.1 | 1.5 |
STD = sexually transmitted disease;
Active syphilis was more prevalent among FSW with no education (2.8%) compared to those with a primary school education (0.8%) or secondary school education (0.6%) (
The factors associated with the syphilis serological markers among FSW in bivariate and multivariate analyses are presented in Table
Factors associated with syphilis serological markers among female sex workers in Burkina Faso.
Characteristics | FSW ( |
Syphilis serological markers (%) | Bivariate analysis | Multivariate analysis | ||||
---|---|---|---|---|---|---|---|---|
OR | 95% CI |
|
aOR | 95% CI |
|
|||
|
||||||||
18-19 | 118 | 3.4 | 1 | — | — | — | — | — |
20–24 | 364 | 3.8 | 1.14 | 0.36–3.53 | 0.820 | — | — | — |
25–29 | 245 | 5.3 | 1.59 | 0.50–5.00 | 0.422 | — | — | — |
≥30 | 318 | 8.8 | 2.75 | 0.94–8.02 | 0.064 | 1.18 | 0.30–4.63 | 0.805 |
All ages | 1045 | 5.6 | ||||||
|
||||||||
None | 324 | 9.3 | 1 | — | — | — | — | — |
Primary | 377 | 5.6 | 0.57 | 0.32–1.03 | 0.063 | 0.62 | 0.33–1.13 | 0.085 |
Secondary | 340 | 2.1 | 0.20 | 0.09–0.47 | <0.001 | 0.23 | 0.09–0. 60 | 0.002 |
|
||||||||
Student | 49 | 8.2 | 1 | — | — | — | — | — |
Worker | 390 | 4.1 | 0.48 | 0.15–1.50 | 0.208 | — | — | — |
Unemployed | 604 | 5.7 | 0.77 | 0.26–2.27 | 0.644 | — | — | — |
|
||||||||
Single | 625 | 4.5 | 1 | — | — | — | — | — |
Married or cohabitating | 102 | 6.9 | 1.57 | 0.66–3.69 | 0.301 | — | — | — |
Divorced/separated/widowed | 318 | 7.5 | 1.74 | 0.99–3.05 | 0.054 | 0.83 | 0.40–1.72 | 0.631 |
|
||||||||
0 | 277 | 2.17 | 1 | |||||
1 | 397 | 5.79 | 2.78 | 1.11–6.91 | 0.028 | 1.69 | 0.56–5.14 | 0.351 |
2+ | 371 | 8.09 | 3.97 | 1.63–9.68 | 0.002 | 1.26 | 0.38–4.15 | 0.706 |
|
||||||||
<1 year | 237 | 2.5 | 1 | — | — | — | — | — |
1–5 years | 506 | 5.3 | 2.17 | 0.88–5.32 | 0.091 | 1.04 | 0.37–2.92 | 0.933 |
6+ years | 286 | 9.1 | 3.85 | 1.56–9.51 | 0.004 | 1.12 | 0.38–3.31 | 0.833 |
|
||||||||
1–14 | 451 | 3.5 | 1 | — | — | — | — | — |
15–21 | 241 | 4.6 | 1.30 | 0.59–2.84 | 0.512 | |||
22–28 | 71 | 9.9 | 2.97 | 1.18–7.50 | 0.021 | 1.97 | 0.73–5.26 | 0.177 |
29–80 | 219 | 11.0 | 3.34 | 1.73–6.44 | <0.001 | 2.62 | 1.28–5.35 | 0.008 |
|
||||||||
No | 188 | 1.6 | 1 | — | — | — | — | — |
Yes | 856 | 6.5 | 4.31 | 1.33–3.94 | 0.014 | 1.68 | 0.38–7.38 | 0.493 |
|
||||||||
No | 403 | 6.9 | 1 | — | — | — | — | — |
Yes | 618 | 5.0 | 0.71 | 0.41–1.19 | 0.190 | 0.65 | 0.35–1.19 | 0.163 |
|
||||||||
No | 573 | 5.2 | 1 | |||||
Yes | 463 | 6.3 | 1.21 | 0.71–2.04 | 0.710 | — | — | — |
|
||||||||
No | 829 | 6.1 | 1 | — | — | — | — | — |
Yes | 213 | 3.8 | 1.20 | 0.71–2.04 | 0.478 | — | — | — |
|
||||||||
Negative | 877 | 5.4 | 1 | |||||
Positive | 168 | 7.1 | 1.35 | 0.70–2.61 | 0.360 | — | — | — |
|
||||||||
Ouagadougou | 349 | 4.3 | 1 | |||||
Bobo-Dioulasso | 350 | 11.4 | 2.87 | 1.56–5.30 | 0.001 | 1.74 | 0.85–3.56 | 0.130 |
Koudougou | 115 | 1.7 | 0.39 | 0.09–1.74 | 0.221 | 0.40 | 0.09–1.88 | 0.248 |
Ouahigouya | 102 | 0.0 | — | — | ||||
Tenkodogo | 129 | 1.5 | 0.35 | 0.08–1.55 | 0.168 | 0.19 | 0.02–1.53 | 0.120 |
|
||||||||
Burkina Faso | 709 | 5.9 | 1 | — | — | — | — | — |
Other countries | 336 | 5.1 | 0.82 | 0.47–1.46 | 0.515 | — | — | — |
STD = sexually transmitted disease; OR = odds ratio; aOR = adjusted odds ratio; CI = confidence interval.
In the bivariate analysis, the risk of syphilis serological markers was 80% lower in participants with at least a secondary school education compared to FSW with no education (OR = 0.20;
In multivariate analysis, after adjustment for age, education level, marital status, number of clients per week, history of pregnancy, use of condoms, and the study city, the number of clients and education level were independently associated with syphilis serological marker carriage. No education was associated with an 77% increase in the risk of syphilis serological marker carriage as compared to a secondary school level of education (aOR = 0.23;
This study found that the prevalence of syphilis serological markers and active syphilis were, respectively, 5.6% and 1.4% among FSW in Burkina Faso. The prevalence varied between study cities. To our knowledge, there are no recent data on syphilis among FSW in Burkina Faso. Overall, it appears that the prevalence of active syphilis (acute) was lower than results found in previous studies in Sub-Saharan Africa. A systematic review of congenital syphilis reported a decrease of 3.01% in syphilis prevalence between 1990 and 1999 and 1.48% between 2000 and 2009 [
Paradoxically, the prevalence of syphilis in our sample was increased, compared to the 2000 data [
In addition, the prevalence of active syphilis in our study remains high in comparison with the estimate of 0.24% found in pregnant women in 2000 [
In our study, the number of cases of active syphilis was low, which limited the ability to further identify factors associated with the acute infection through multivariate analysis. We instead used syphilis serological markers for analysis purposes. Furthermore, self-reporting sexual behavior in a context of social stigmatization of and discrimination toward FSW may have led to social desirability bias; however, this did not have impact on the prevalence of syphilis, as this was evaluated through syphilis serological markers. Our study provides updated data on syphilis serological markers in Burkina Faso.
This study provided updated epidemiological data on syphilis based on rapid diagnostic testing in situ among sex workers in Burkina Faso. We found that syphilis prevalence among FSW was relatively high and requires targeted preventive measures. Screening with rapid diagnostic tests followed by a single-dose administration of penicillin could be an effective approach to control syphilis among FSW and thus contribute to the prevention of HIV transmission. Safer sex and HIV prevention activities for FSW offer an opportunity to integrate screening and early treatment of syphilis.
The datasets used during the current study are available from the corresponding author on reasonable request.
The authors declare that there are no conflicts of interest regarding the publication of this article.
S. Baral, S. Kouanda, H. G. Ouedraogo, O. Ky-Zerbo, and A. Grosso conceptualized the study and contributed to study design, implementation, and manuscript writing; I.B. Meda and I. Zongo assisted in manuscript writing; B. C. Samadoulougou and G. Tarnagda helped in study implementation, data cleaning, and manuscript review; K. Cissé, A. Sondo, N. Sawadogo, Y. Traore, and Nicolas Barro conducted the manuscript review.
The authors acknowledged the USAID-Project SEARCH, Task Order No. 2, the Global Fund to Fight AIDS, Tuberculosis, and Malaria, the Permanent Secretary of the National Council against AIDS (SP/CNLS), Burkina Faso, the Yerelon Association in Bobo-Dioulasso and all other associations that were involved in this study. They are grateful to all the study participants. The USAID and Project SEARCH, Task Order no. 2, are funded by the US Agency for International Development under Contract no. GHH-I-00-0700,032-00, beginning from September 30, 2008, and supported by the President’s Emergency Plan for AIDS Relief. The Research to Prevention Project is led by the Johns Hopkins Center for Global Health and managed by the Johns Hopkins Bloomberg School of Public Health Center for Communication Programs.