Treponema pallidum Infection in Primates: Clinical Manifestations, Epidemiology, and Evolution of a Stealthy Pathogen

Abstract

In humans, subspecies of the bacterium Treponema pallidum cause syphilis as well as the nonsexually transmitted diseases yaws and bejel. The origin of T. pallidum infection in humans is controversial, and as a result attention has focused on the presence of this pathogen in wild nonhuman primates. It has been known for some time that Old World nonhuman primates, including gorillas, chimpanzees, baboons, and patas monkeys, are infected with T. pallidum in the wild. However, the bulk of studies on treponemal disease in wild apes and monkeys were performed in the 1960s and 1970s and focused on animals captured in West Africa. Due to the absence of relevant molecular biological assays during this time period, virtually all studies relied on the serological screening of animals. In this chapter, we describe the findings of this decades-old body of research, as well as more recent results which utilize DNA-based methods to demonstrate the presence of treponemal disease in East African baboons. We discuss the distribution and protean clinical manifestations of T. pallidum infection in wild nonhuman primates, host factors involved in human and simian infections, the genetic relationship between human and nonhuman primate strains, and implications for understanding the evolution of this pathogen and its primate hosts.