The genomes of the yaws bacterium, Treponema pallidum subsp. pertenue, of nonhuman primate and human origin are not genomically distinct

Abstract

BackgroundTreponema pallidumsubsp.pertenue(TPE) is the causative agent of human yaws. Yaws is currently reported in 13 endemic countries in Africa, southern Asia, and the Pacific region. During the mid-20th century, a first yaws eradication effort resulted in a global 95% drop in yaws prevalence. The lack of continued surveillance has led to the resurgence of yaws. The disease was believed to have no animal reservoirs, which supported the development of a currently ongoing second yaws eradication campaign. Concomitantly, genetic evidence started to show thatTPEstrains naturally infect nonhuman primates (NHPs) in sub-Saharan Africa. In our current study we tested hypothesis that NHP- and human-infectingTPEstrains differ in the previously unknown parts of the genomes.Methodology/Principal findingsIn this study, we determined complete (finished) genomes of tenTPEisolates that originated from NHPs and compared them toTPEwhole-genome sequences from human yaws patients. We performed an in-depth analysis ofTPEgenomes to determine if any consistent genomic differences are present betweenTPEgenomes of human and NHP origin. We were able to resolve previously undeterminedTPEchromosomal regions (sequencing gaps) that prevented us from making a conclusion regarding the sequence identity ofTPEgenomes from NHPs and humans. The comparison among finished genome sequences revealed no consistent differences between human and NHPTPEgenomes.Conclusion/SignificanceOur data show that NHPs are infected with strains that are not only similar to the strains infecting humans but are genomically indistinguishable from them. Although interspecies transmission in NHPs is a rare event and evidence for current spillover events is missing, the existence of the yaws bacterium in NHPs is demonstrated. While the low risk of spillover supports the current yaws treatment campaign, it is of importance to continue yaws surveillance in areas where NHPs are naturally infected withTPEeven if yaws is successfully eliminated in humans.