Rapid radiation of treponema pallidum pertenue in wild non-human primates

Bacteria of the species Treponema pallidum are causative agents of venereal syphilis (Treponema pallidum pallidum), Bejel (T. p. endemicum), and yaws (T. p. pertenue) in humans. We documented Treponema pallidum infections associated with disease in wild sooty mangabeys (Cercocebus atys) in Taï National Park, Côte d’Ivoire, and green monkeys (Chlorocebus sabaeus) from Bijilo Forest Park, Gambia and Niokolo-Koba National Park, Senegal. To examine the evolutionary relatedness of these treponemes to those responsible for diseases in humans and for previously documented infections in baboons (Papio papio), we conducted a hybridization capture experiment to enrich Treponema pallidum DNA from samples collected from symptomatic individuals. This approach allowed us to sequence the full genomes of Treponema pallidum strains infecting sooty mangabeys (n = 2) and green monkeys (n = 4). Phylogenomic analyses revealed that all Treponema pallidum strains infecting non-human primates are most closely related to the sub-species T. p. pertenue. Strains infecting humans and non-human primates do not appear to be reciprocally monophyletic. The star-like phylogenetic branching pattern of the T. p. pertenue clade, with short basal branches receiving low statistical support, suggests a rapid initial radiation across humans and non-human primates. These results greatly broaden the known host range of T.p. pertenue and suggest the existence of a vast zoonotic reservoir that could possibly contribute to the failure of global eradication efforts.