Prevalence of syphilis and associated factors among female sex workers in Ethiopia: findings from a multilevel analysis of a national bio-behavioral survey

Background Syphilis is a highly contagious sexually transmitted infection posing a significant public health challenge, especially in developing countries, including sub-Saharan Africa. Female sex workers are exposed to sexually transmitted infections, including syphilis, because of their sexual behavior and limited access to health services. However, data on national syphilis prevalence estimates and the associated factors are scarce in Ethiopia. This, as well as our limited knowledge about the extent of clustering among female sex workers in the country, is a critical gap in information we aimed to fill through this analysis. Methods The study was a cross-sectional, bio-behavioral survey conducted among female sex workers in six cities and ten major towns in Ethiopia. Participants were selected using a respondent-driven sampling method. Survey participants provided blood samples for syphilis, HIV, and hepatitis serological testing. Survey data were collected via an interviewer-administered questionnaire. In this analysis, we employed descriptive statistics to summarize data on the study variables. In addition, we used multilevel bivariable and multivariable logistic regression models to examine the association between independent variables and the dependent variable (syphilis prevalence) while accounting for the clustering effect. Result A total of 6085 female sex workers participated in the survey. Their median age [Interquartile Range (IQR) was 25 (8)] years, and a majority (96.1%) were in the 20-24-year-old age group. The prevalence of syphilis among female sex workers in Ethiopia's six cities and ten major towns was 6.2%. Being in the age group of 30-34 (AOR = 2.64; 95% CI = 1.40, 4.98) and 35-59 (AOR = 4.7; 95% CI = 2.5, 8.86), being divorced/widowed (AOR = 1.37; 95% CI = 1.03, 1.82), having no formal education (AOR = 3.38; 95% CI = 2.34, 5.11), primary 1st cycle (grades 1-4) education (AOR = 2.77; 95% CI = 1.79, 4.30), and having primary 2nd cycle (grades 5-8) education (AOR = 1.80; 95% CI = 1.21, 2.69) were significantly associated with syphilis among female sex workers. Conclusion The prevalence of syphilis among female sex workers was high. Being divorced/widowed or in the older age group and having a low level of education were significantly associated with an increased risk of syphilis. The high prevalence and associated factors identified need to be considered in planning comprehensive interventions to control syphilis among female sex workers in Ethiopia.