Molecular and serological evidence of systemic Treponema pallidum infection in wild western chimpanzees.

Human treponematoses are chronic diseases caused by closely related Treponema species. Increasing evidence of yaws-like Treponema pallidum subsp. pertenue infections in nonhuman primates raises concerns about pathogen persistence in natural ecosystems. Here, we investigated treponemal infection in western chimpanzees (Pan troglodytes verus) using molecular and serological analyses of postmortem skeletal remains from three deceased individuals. Anti-T. pallidum antibodies were detected in all chimpanzees using validated serological assays, while molecular assays identified T. pallidum DNA in a vertebral bone sample from one individual, supporting systemic dissemination. By integrating forensic findings with retrospective field video observations, we identified concordance between molecular bone involvement and advanced clinical manifestations, including genital lesions and facial depigmentation, in the same chimpanzee. These findings provide rare evidence linking systemic treponemal dissemination to severe disease in a wild endangered great ape and highlight the importance of enhanced surveillance for wildlife conservation and for assessing potential implications for human yaws eradication efforts.