Syphilis diagnosis and serological response to Benzathine Penicillin G among patients attending HIV clinics in N’Djaména, Chad

Background: Syphilis is endemic in the Sub-Saharan zone and disproportionately affects at-risk populations such as men who have sex with men, sex workers and HIV infected individuals. In this study, we measure the impact of syphilis among people living with HIV in the Republic of Chad, where no data are currently available. Method: Outpatients attending 2 HIV clinics in N’Djamena, Republic of Chad, were tested for syphilis. Subjects who tested positive for both non-treponemal (VDRL) and treponemal (TPHA) received a single dose of Benzathine Penicillin G, 2.4 MU. An additional VDRL test was performed 6 months after treatment to ensure appropriate serological response. Results: Of 207 patients included, 29 (14%) tested positive for VDRL at the first visit, with moderate/low antibody titers (ranging from 1/2 to 1/8); 24 (82.6%) of these had treponemal immunization confirmed by TPHA test. Six months after Benzathine Penicillin treatment, 22/24 of the patients (91.6%) tested negative for VDRL, and 2 showed a 4-fold titer decline. Conclusion: This first study in the Republic of Chad suggests that syphilis infection is frequent among people living with HIV in this country. Systematic screening of syphilis should be considered in this population