Widespread Treponema pallidum Infection in Nonhuman Primates, Tanzania.

We investigated Treponema pallidum infection in 8 nonhuman primate species (289 animals) in Tanzania during 2015-2017. We used a serologic treponemal test to detect antibodies against the bacterium. Infection was further confirmed from tissue samples of skin-ulcerated animals by 3 independent PCRs (polA, tp47, and TP_0619). Our findings indicate that T. pallidum infection is geographically widespread in Tanzania and occurs in several species (olive baboons, yellow baboons, vervet monkeys, and blue monkeys). We found the bacterium at 11 of 14 investigated geographic locations. Anogenital ulceration was the most common clinical manifestation; orofacial lesions also were observed. Molecular data show that nonhuman primates in Tanzania are most likely infected with T. pallidum subsp. pertenue-like strains, which could have implications for human yaws eradication.

Female post-copulatory behavior in a group of olive baboons (Papio anubis) infected by Treponema pallidum.

Pathogens exert a profound and pervasive cost on various aspects of primate sociality and reproduction. In olive baboons (Papio anubis) at Lake Manyara National Park, Tanzania, genital skin ulcers, caused by the bacterium Treponema pallidum subsp. pertenue, are associated with increased female mating avoidance and altered male mating patterns at a pre-copulatory and copulatory level. Beyond this, mating is also comprised of post-copulatory interactions among sexual partners (i.e., copulation calls, darting [post-copulatory sprint away from the male], and post-copulatory grooming). In baboons, female post-copulatory behavior is hypothesized to incite male-male competition, promote subsequent copulations, and/or strengthen the bonds between the mating pairs. Due to a higher reproductive burden (i.e. pregnancy, lactation, infant rearing), females should avoid proceptive behavior after mating to decrease further exposure to potential pathogens. To investigate whether the presence of genital skin ulcers has an impact at the post-copulatory level, we analyzed 517 copulation events of 33 cycling females and 29 males with and without genital skin ulcers. The occurrence of female post-copulatory behaviors was not altered by genital skin ulcerations in males. Similar to other baboon populations, females in our study group were more likely to utter copulation calls after an ejaculatory copulation. The likelihood of darting was higher after ejaculatory copulations and with the presence of copulation calls. Post-copulatory grooming (i.e., occurring within 15 seconds after a copulation) was not frequently observed. Our results indicate that despite the presence of conspicuous signs of disease, female post-copulatory behavior was not affected by the genital health status of the males. This indicates that in our study group, infection cues caused by T. pallidum subsp. pertenue play a major role before and during mating, but not after mating. The post-copulatory behavior of females is most likely affected by physiological or evolutionary constraints other than sexually transmitted infections.