Treponemal Shedding, Load, and Viability, in Women and Men-who-have-sex-with-women-only With Early Infectious Syphilis: Implications for Transmission

How syphilis is transmitted between sexual partners is unclear. Asymptomatic detection i.e. detection of syphilis bacteria (Tp) from anatomical sites without lesions, in patients with syphilis infection, suggests that asymptomatic transmission from these sites may play a role. However, no existing studies have established whether the syphilis bacteria (Tp) detected was viable. This means it is not known if the bacteria at this anatomical site is alive and therefore able to transmit the infection. Further, studies have focused mostly on men who have sex with men, resulting in a lack of evidence regarding anal shedding in men-who-have-sex-with-women only and women (regardless of sexual behaviour), and no data on asymptomatic vaginal shedding in women. This study will explore: 1. Patterns of Tp detection in women and men-who-have-sex-with-women only. 2. Whether detected Tp from each asymptomatic anatomical sites is viable 3. Duration of Tp detection and viability (alive and transmissible bacteria). Patients presenting to a participating sexual health service (overseas only) for management of suspected/confirmed early infectious syphilis will be eligible. During the routine clinical examination, participants will have additional oral and anal swabs, urine, vaginal swab (where relevant), penile skin swab (where relevant) and blood sample collected, in addition to the routine samples taken from the same sites and routine serology collected when syphilis is diagnosed.

NCT Number	NCT07300254
Lead Sponsor	Monash University Collaborators: Melbourne Sexual Health Centre, The Alfred
Conditions	Syphilis
Enrollment	480 participants
Start Date	2025-12-02
Primary Completion	2027-06-30 (estimated)
Study Completion	2028-12-31 (estimated)
Updated on ClinicalTrials.gov	2026-04-03