Neuro-ophthalmological study of late yaws and pinta. II. The Caracas project

Treponematosis in critically endangered Western chimpanzees (Pan troglodytes verus) in Senegal

Treponematoses encompass a group of chronic and debilitating bacterial diseases transmitted sexually or by direct contact and attributed to Treponema pallidum. Despite being documented since as far back as 1963, the epidemiology of treponematoses in wild primates has remained an uninvestigated territory due to the inherent challenges associated with conducting examinations and obtaining invasive biological samples from wild animals. The primary aim of this study was to investigate the presence of treponemal infections in the critically endangered Western chimpanzees in Senegal, utilizing an innovative non-invasive stool serology method. We provide compelling evidence of the existence of anti-Treponema-specific antibodies in 13 out of 29 individual chimpanzees. Our study also underscores the significant potential of stool serology as a valuable non-invasive tool for monitoring and surveilling crucial emerging diseases in wild animals. We recognize two major implications: (1) the imperative need to assess the risks of treponematosis in Western chimpanzee populations and (2) the necessity to monitor and manage this disease following a holistic One Health approach.

Geographically structured genomic diversity of non-human primate-infecting Treponema pallidum subsp. pertenue

Many non-human primate species in sub-Saharan Africa are infected with Treponema pallidum subsp. pertenue, the bacterium causing yaws in humans. In humans, yaws is often characterized by lesions of the extremities and face, while T. pallidum subsp. pallidum causes venereal syphilis and is typically characterized by primary lesions on the genital, anal or oral mucosae. It remains unclear whether other T. pallidum subspecies found in humans also occur in non-human primates and how the genomic diversity of non-human primate T. pallidum subsp. pertenue lineages is distributed across hosts and space. We observed orofacial and genital lesions in sooty mangabeys (Cercocebus atys) in Taï National Park, Côte d'Ivoire and collected swabs and biopsies from symptomatic animals. We also collected non-human primate bones from 8 species in Taï National Park and 16 species from 11 other sites across sub-Saharan Africa. Samples were screened for T. pallidum DNA using polymerase chain reactions (PCRs) and we used in-solution hybridization capture to sequence T. pallidum genomes. We generated three nearly complete T. pallidum genomes from biopsies and swabs and detected treponemal DNA in bones of six non-human primate species in five countries, allowing us to reconstruct three partial genomes. Phylogenomic analyses revealed that both orofacial and genital lesions in sooty mangabeys from Taï National Park were caused by T. pallidum subsp. pertenue. We showed that T. pallidum subsp. pertenue has infected non-human primates in Taï National Park for at least 28 years and has been present in two non-human primate species that had not been described as T. pallidum subsp. pertenue hosts in this ecosystem, western chimpanzees (Pan troglodytes verus) and western red colobus (Piliocolobus badius), complementing clinical evidence that started accumulating in Taï National Park in 2014. More broadly, simian T. pallidum subsp. pertenue strains did not form monophyletic clades based on host species or the symptoms caused, but rather clustered based on geography. Geographical clustering of T. pallidum subsp. pertenue genomes might be compatible with cross-species transmission of T. pallidum subsp. pertenue within ecosystems or environmental exposure, leading to the acquisition of closely related strains. Finally, we found no evidence for mutations that confer antimicrobial resistance.

Serosurvey of Treponema pallidum infection among children with skin ulcers in the Tarangire-Manyara ecosystem, northern Tanzania

BACKGROUND

The first yaws eradication campaign reduced the prevalence of yaws by 95%. In recent years, however, yaws has reemerged and is currently subject to a second, ongoing eradication campaign. Yet, the epidemiological status of Tanzania and 75 other countries with a known history of human yaws is currently unknown. Contrary to the situation in humans in Tanzania, recent infection of nonhuman primates (NHPs) with the yaws bacterium Treponema pallidum subsp. pertenue (TPE) have been reported. In this study, we consider a One Health approach to investigate yaws and describe skin ulcers and corresponding T. pallidum serology results among children living in the Tarangire-Manyara ecosystem, an area with increasing wildlife-human interaction in northern Tanzania.

METHODS

To investigate human yaws in Tanzania, we conducted a cross-sectional study to screen and interview skin-ulcerated children aged 6 to 15 years, who live in close proximity to two national parks with high numbers of naturally TPE-infected monkeys. Serum samples from children with skin ulcers were tested for antibodies against the bacterium using a treponemal (Treponema pallidum Particle Agglutination assay) and a non-treponemal (Rapid Plasma Reagin) test.

RESULTS

A total of 186 children aged between 6 and 15 years (boys: 10.7 ± 2.1 (mean ± SD), N = 132; girls: 10.9 ± 2.0 (mean ± SD), N = 54) were enrolled. Seven children were sampled at health care facilities and 179 at primary schools. 38 children (20.4%) reported active participation in bushmeat hunting and consumption and 26 (13.9%) reported at least one physical contact with a NHP. None of the lesions seen were pathognomonic for yaws. Two children tested positive for treponemal antibodies (1.2%) in the treponemal test, but remained negative in the non-treponemal test.

CONCLUSIONS

We found no serological evidence of yaws among children in the Tarangire-Manyara ecosystem. Nevertheless, the close genetic relationship of human and NHPs infecting TPE strains should lead to contact prevention with infected NHPs. Further research investigations are warranted to study the causes and possible prevention measures of spontaneous chronic ulcers among children in rural Tanzania and to certify that the country is free from human yaws.

Epidemic of venereal treponematosis in wild monkeys: a paradigm for syphilis origin

Treponema pallidum infections have been primarily known as slightly contagious mucocutaneous infections called yaws (tropical Africa and America) and bejel (subtropical North Africa). T. pallidum emerged as a highly infectious venereal syphilis agent in South America, probably about 500 years ago, and because of its venereal transmission, it quickly caused a worldwide pandemic. The disease manifests as lesions, including a chancre; then antibodies become detectable when or slightly after the chancre appears, and before the development of a rash and other systemic manifestations. Venereal diseases are poorly known in monkeys. During fieldwork in Senegal, we discovered an epizootic outbreak of venereal disease that we explored. We detected a venereal form of T. pallidum subsp. pertenue infection in green monkeys (Chlorocebus sabaeus), then observed an epizootic outbreak in Senegal and its spread among baboons a year later. Comparative analysis of T. pallidum genomes from the monkeys' chancres and other Treponema genomes showed an acceleration of the number of single nucleotide polymorphisms, comparable to that observed in syphilis. Identified T. pallidum clones seem to be epizootic through the acceleration of their mutation rate, which is linked to their larger diffusion.

Epidemiological situation of yaws in the Americas: A systematic review in the context of a regional elimination goal

BACKGROUND

Yaws is targeted for eradication by 2020 in the WHA66.12 resolution of the World Health Assembly. The objective of this study was to describe the occurrence of yaws in the Americas and to contribute to the compilation of evidence based on published data to undertake the certification of yaws eradication.

METHODOLOGY

A systematic review of the epidemiological situation of yaws in the Americas was performed by searching in MEDLINE, Embase, LILACS, SCOPUS, Web of Science, DARE and Cochrane Database of Systematic Reviews. Experts on the topic were consulted, and institutional WHO/PAHO library databases were reviewed.

PRINCIPAL FINDINGS

Seventy-five full-text articles published between 1839 and 2012 met the inclusion criteria. Haiti and Jamaica were the two countries with the highest number of papers (14.7% and 12.0%, respectively). Three-quarters of the studies were conducted before 1970. Thirty-three countries reported yaws case count or prevalence data. The largest foci in the history were described in Brazil and Haiti. The most recent cases reported were recorded in eight countries: Suriname, Guyana, Colombia, Haiti, Martinique, Dominica, Trinidad and Tobago, and Brazil. Gaps in information and heterogeneity were detected in the methodologies used and outcome reporting, making cross-national and chronological comparisons difficult.

CONCLUSIONS

The lack of recent yaws publications may reflect, in the best-case scenario, the interruption of yaws transmission. It should be possible to reach the eradication goal in the region of the Americas, but it is necessary to collect more information. We suggest updating the epidemiological status of yaws, especially in two countries that need to assess ongoing transmission. Twenty-four countries need to demonstrate the interruption of transmission and declare its status of yaws endemicity, and sixteen countries should declare if they are yaws-free. It is necessary to formally verify the achievement of this goal in Ecuador.

Topical treatment with gallium maltolate reduces Treponema pallidum subsp. pertenue burden in primary experimental lesions in a rabbit model of yaws

Background

Gallium is a semi-metallic element known since the 1930s to have antimicrobial activity. This activity stems primarily from gallium's ability to mimic trivalent iron and disrupt specific Fe(III)-dependent pathways, particularly DNA synthesis (due to inhibition of ribonucleotide reductase). Because of its novel mechanism of action, gallium is currently being investigated as a new antibacterial agent, particularly in light of the increasing resistance of many pathogenic bacteria to existing antibiotics. Gallium maltolate (GaM) is being developed as an orally and topically administrable form of gallium. Yaws is a neglected tropical disease affecting mainly the skin and skeletal system of children in underprivileged settings. It is currently the object of a WHO-promoted eradication campaign using mass administration of the macrolide azithromycin, an antibiotic to which the yaws agent Treponema pallidum subsp. pertenue has slowly begun to develop genetic resistance.

Methods

Because yaws transmission is mainly due to direct skin contact with an infectious skin lesion, we evaluated the treponemicidal activity of GaM applied topically to skin lesions in a rabbit model of yaws. Treatment efficacy was evaluated by measuring lesion diameter, treponemal burden in lesion aspirates as determined by dark field microscopy and amplification of treponemal RNA, serology, and immunohistochemistry of biopsied tissue samples.

Results

Our results show that topical GaM was effective in reducing treponemal burden in yaws experimental lesions, particularly when applied at the first sign of lesion appearance but, as expected, did not prevent pathogen dissemination.

Conclusion

Early administration of GaM to yaws lesions could reduce the infectivity of the lesions and thus yaws transmission, potentially contributing to current and future yaws control campaigns.

Yaws is a neglected tropical disease affecting children in underprivileged countries, transmitted through direct skin contact with an active lesion. This infection, although rarely fatal, can lead to disfigurement and serious disability. The World Health Organization is currently conducting a yaws eradication effort that employs mass administration of azithromycin, an antibiotic against which the yaws pathogen has slowly begun to develop genetic resistance. Because this phenomenon has the potential to undermine the eradication effort, we investigated the antimicrobial activity of gallium maltolate, which has a novel mechanism of action, against the yaws pathogen. Our initial results show that topical application of gallium maltolate has significant treponemicidal activity, and suggest that this compound might find an application in the effort to eradicate yaws. Future studies will evaluate whether oral administration of gallium maltolate is as effective as the antibiotics currently approved for yaws treatment to clear systemic infection.

Gene target selection for loop-mediated isothermal amplification for rapid discrimination of Treponema pallidum subspecies

We show proof of concept for gene targets (polA, tprL, and TP_0619) that can be used in loop-mediated isothermal amplification (LAMP) assays to rapidly differentiate infection with any of the three Treponema pallidum subspecies (pallidum (TPA), pertenue (TPE), and endemicum (TEN)) and which are known to infect humans and nonhuman primates (NHPs). Four TPA, six human, and two NHP TPE strains, as well as two human TEN strains were used to establish and validate the LAMP assays. All three LAMP assays were highly specific for the target DNA. Amplification was rapid (5-15 min) and within a range of 10E+6 to 10E+2 of target DNA molecules. Performance in NHP clinical samples was similar to the one seen in human TPE strains. The newly designed LAMP assays provide proof of concept for a diagnostic tool that enhances yaws clinical diagnosis. It is highly specific for the target DNA and does not require expensive laboratory equipment. Test results can potentially be interpreted with the naked eye, which makes it suitable for the use in remote clinical settings.

Survey of Treponemal Infections in Free-Ranging and Captive Macaques, 1999-2012

Survey results showed treponemal infection among pet macaques in Southeast Asia, a region with a high prevalence of human yaws. This finding, along with studies showing treponemal infection in nonhuman primates in Africa, should encourage a One Health approach to yaws eradication and surveillance activities, possibly including monitoring of nonhuman primates in yaws-endemic regions.

Isolation of Treponema DNA from Necrophagous Flies in a Natural Ecosystem

Background

Recently, the World Health Organization launched a campaign to eradicate the tropical disease yaws, caused by the bacterium Treponema pallidum subsp. pertenue; however, for decades researchers have questioned whether flies act as a vector for the pathogen that could facilitate transmission.

Methods

A total of 207 fly specimens were trapped in areas of Africa in which T. pallidum-induced skin ulcerations are common in wild baboons; 88 flies from Tarangire National Park and 119 from Lake Manyara National Park in Tanzania were analyzed by PCR for the presence of T. pallidum DNA.

Findings

We report that in the two study areas, T. pallidum DNA was found in 17–24% of wild-caught flies of the order Diptera. Treponemal DNA sequences obtained from many of the flies match sequences derived from nearby baboon T. pallidum strains, and one of the fly species with an especially high prevalence of T. pallidum DNA, Musca sorbens, has previously been shown to transmit yaws in an experimental setting.

Interpretation

Our results raise the possibility that flies play a role in yaws transmission; further research is warranted, given how important understanding transmission is for the eradication of this disfiguring disease.

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Treponema pallidum DNA was found in 17–24% of wild-caught flies in the Manyara region of Tanzania.

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Results further support the possibility that flies play a role in yaws transmission.

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New theoretic route of inter-species transmission for Treponema

The discovery of Treponema pallidum DNA on necrophagous flies in Africa supports historical reports on possible transmission of the bacterium by flies as a mechanical vector. The bacterium (subsp. pertenue) causes human yaws, which is currently subject to eradication efforts. It has been shown that African nonhuman primates are also found to be infected with T. pallidum strains that are closely related to human yaws causing strains. The ecology of T. pallidum infection in primates is not yet fully understood and intra- and interspecies transmission pathways, apart from skin-to-skin contact in humans, are largely unknown.

High Prevalence of Antibodies against the Bacterium Treponema pallidum in Senegalese Guinea Baboons (Papio papio)

The bacterium Treponema pallidum is known to cause syphilis (ssp. pallidum), yaws (ssp. pertenue), and endemic syphilis (ssp. endemicum) in humans. Nonhuman primates have also been reported to be infected with the bacterium with equally versatile clinical manifestations, from severe skin ulcerations to asymptomatic. At present all simian strains are closely related to human yaws-causing strains, an important consideration for yaws eradication. We tested clinically healthy Guinea baboons (Papio papio) at Parc National Niokolo Koba in south eastern Senegal for the presence of anti-T. pallidum antibodies. Since T. pallidum infection in this species was identified 50 years ago, and there has been no attempt to treat non-human primates for infection, it was hypothesized that a large number of West African baboons are still infected with simian strains of the yaws-bacterium. All animals were without clinical signs of treponematoses, but 18 of 20 (90%) baboons tested positive for antibodies against T. pallidum based on treponemal tests. Yet, Guinea baboons seem to develop no clinical symptoms, though it must be assumed that infection is chronic or comparable to the latent stage in human yaws infection. The non-active character is supported by the low anti-T. pallidum serum titers in Guinea baboons (median = 1:2,560) versus serum titers that are found in genital-ulcerated olive baboons with active infection in Tanzania (range of medians among the groups of initial, moderate, and severe infected animals = 1:15,360 to 1:2.097e+7). Our findings provide evidence for simian infection with T. pallidum in wild Senegalese baboons. Potentially, Guinea baboons in West Africa serve as a natural reservoir for human infection, as the West African simian strain has been shown to cause sustainable yaws infection when inoculated into humans. The present study pinpoints an area where further research is needed to support the currently on-going second WHO led yaws eradication campaign with its goal to eradicate yaws by 2020.

Challenges and key research questions for yaws eradication

Yaws is endemic in west Africa, southeast Asia, and the Pacific region. To eradicate yaws by 2020, WHO has launched a campaign of mass treatment with azithromycin. Progress has been made towards achievement of this ambitious goal, including the validation of point-of-care and molecular diagnostic tests and piloting of the strategy in several countries, including Ghana, Vanuatu, and Papua New Guinea. Gaps in knowledge need to be addressed to allow refinement of the eradication strategy. Studies exploring determinants of the spatial distribution of yaws are needed to help with the completion of baseline mapping. The finding that Haemophilus ducreyi causes lesions similar to yaws is particularly important and further work is needed to assess the effect of azithromycin on these lesions. The integration of diagnostic tests into different stages of the eradication campaign needs investigation. Finally, studies must be done to inform the optimum mass-treatment strategy for sustainable interruption of transmission.

Validation of serological tests for the detection of antibodies against Treponema pallidum in nonhuman primates

There is evidence to suggest that the yaws bacterium (Treponema pallidum ssp. pertenue) may exist in non-human primate populations residing in regions where yaws is endemic in humans. Especially in light of the fact that the World Health Organizaiton (WHO) recently launched its second yaws eradication campaign, there is a considerable need for reliable tools to identify treponemal infection in our closest relatives, African monkeys and great apes. It was hypothesized that commercially available serological tests detect simian anti-T. pallidum antibody in serum samples of baboons, with comparable sensitivity and specificity to their results on human sera. Test performances of five different treponemal tests (TTs) and two non-treponemal tests (NTTs) were evaluated using serum samples of 57 naturally T. pallidum-infected olive baboons (Papio anubis) from Lake Manyara National Park in Tanzania. The T. pallidum particle agglutination assay (TP-PA) was used as a gold standard for comparison. In addition, the overall infection status of the animals was used to further validate test performances. For most accurate results, only samples that originated from baboons of known infection status, as verified in a previous study by clinical inspection, PCR and immunohistochemistry, were included. All tests, TTs and NTTs, used in this study were able to reliably detect antibodies against T. pallidum in serum samples of infected baboons. The sensitivity of TTs ranged from 97.7-100%, while specificity was between 88.0-100.0%. The two NTTs detected anti-lipoidal antibodies in serum samples of infected baboons with a sensitivity of 83.3% whereas specificity was 100%. For screening purposes, the TT Espline TP provided the highest sensitivity and specificity and at the same time provided the most suitable format for use in the field. The enzyme immune assay Mastblot TP (IgG), however, could be considered as a confirmatory test.

The endemic treponematoses

The agents of human treponematoses include four closely related members of the genus Treponema: three subspecies of Treponema pallidum plus Treponema carateum. T. pallidum subsp. pallidum causes venereal syphilis, while T. pallidum subsp. pertenue, T. pallidum subsp. endemicum, and T. carateum are the agents of the endemic treponematoses yaws, bejel (or endemic syphilis), and pinta, respectively. All human treponematoses share remarkable similarities in pathogenesis and clinical manifestations, consistent with the high genetic and antigenic relatedness of their etiological agents. Distinctive features have been identified in terms of age of acquisition, most common mode of transmission, and capacity for invasion of the central nervous system and fetus, although the accuracy of these purported differences is debated among investigators and no biological basis for these differences has been identified to date. In 2012, the World Health Organization (WHO) officially set a goal for yaws eradication by 2020. This challenging but potentially feasible endeavor is favored by the adoption of oral azithromycin for mass treatment and the currently focused distribution of yaws and endemic treponematoses and has revived global interest in these fascinating diseases and their causative agents.

Fine analysis of genetic diversity of the tpr gene family among treponemal species, subspecies and strains

Background

The pathogenic non-cultivable treponemes include three subspecies of Treponema pallidum (pallidum, pertenue, endemicum), T. carateum, T. paraluiscuniculi, and the unclassified Fribourg-Blanc treponeme (Simian isolate). These treponemes are morphologically indistinguishable and antigenically and genetically highly similar, yet cross-immunity is variable or non-existent. Although all of these organisms cause chronic, multistage skin and systemic disease, they have historically been classified by mode of transmission, clinical presentations and host ranges. Whole genome studies underscore the high degree of sequence identity among species, subspecies and strains, pinpointing a limited number of genomic regions for variation. Many of these “hot spots” include members of the tpr gene family, composed of 12 paralogs encoding candidate virulence factors. We hypothesize that the distinct clinical presentations, host specificity, and variable cross-immunity might reside on virulence factors such as the tpr genes.

Methodology/Principal Findings

Sequence analysis of 11 tpr loci (excluding tprK) from 12 strains demonstrated an impressive heterogeneity, including SNPs, indels, chimeric genes, truncated gene products and large deletions. Comparative analyses of sequences and 3D models of predicted proteins in Subfamily I highlight the striking co-localization of discrete variable regions with predicted surface-exposed loops. A hallmark of Subfamily II is the presence of chimeric genes in the tprG and J loci. Diversity in Subfamily III is limited to tprA and tprL.

Conclusions/Significance

An impressive sequence variability was found in tpr sequences among the Treponema isolates examined in this study, with most of the variation being consistent within subspecies or species, or between syphilis vs. non-syphilis strains. Variability was seen in the pallidum subspecies, which can be divided into 5 genogroups. These findings support a genetic basis for the classification of these organisms into their respective subspecies and species. Future functional studies will determine whether the identified genetic differences relate to cross-immunity, clinical differences, or host ranges.

Pathogenic treponemes include three subspecies of Treponema pallidum (pallidum, pertenue, endemicum), T. carateum, T. paraluiscuniculi, and the unclassified Fribourg-Blanc treponeme. Although they share morphology and have very similar antigenic profiles, they have traditionally been distinguished by mode of transmission, host specificity and the clinical manifestations that they cause. The molecular basis for these disease characteristics is not known. Comparative genomics has revealed that sequences differences among the species and subspecies are found in very localized regions of the chromosome. Many of these regions of sequence variation are found in the tpr genes, which encode a family of twelve candidate virulence factors, many of which are predicted to be outer membrane proteins. Most of the tpr-specific sequence changes are consistent within subspecies or species, supporting the historical classification of these organisms into separate subspecies and species. Functional studies are needed to determine whether any of the tpr gene differences are related to differences in host range, immunity, or clinical manifestations.

Whole genome sequence of the Treponema Fribourg-Blanc: unspecified simian isolate is highly similar to the yaws subspecies

Background

Unclassified simian strain Treponema Fribourg-Blanc was isolated in 1966 from baboons (Papio cynocephalus) in West Africa. This strain was morphologically indistinguishable from T. pallidum ssp. pallidum or ssp. pertenue strains, and it was shown to cause human infections.

Methodology/Principal Findings

To precisely define genetic differences between Treponema Fribourg-Blanc (unclassified simian isolate, FB) and T. pallidum ssp. pertenue strains (TPE), a high quality sequence of the whole Fribourg-Blanc genome was determined with 454-pyrosequencing and Illumina sequencing platforms. Combined average coverage of both methods was greater than 500×. Restriction target sites (n = 1,773), identified in silico, of selected restriction enzymes within the Fribourg-Blanc genome were verified experimentally and no discrepancies were found. When compared to the other three sequenced TPE genomes (Samoa D, CDC-2, Gauthier), no major genome rearrangements were found. The Fribourg-Blanc genome clustered with other TPE strains (especially with the TPE CDC-2 strain), while T. pallidum ssp. pallidum strains clustered separately as well as the genome of T. paraluiscuniculi strain Cuniculi A. Within coding regions, 6 deletions, 5 insertions and 117 substitutions differentiated Fribourg-Blanc from other TPE genomes.

Conclusions/Significance

The Fribourg-Blanc genome showed similar genetic characteristics as other TPE strains. Therefore, we propose to rename the unclassified simian isolate to Treponema pallidum ssp. pertenue strain Fribourg-Blanc. Since the Fribourg-Blanc strain was shown to cause experimental infection in human hosts, non-human primates could serve as possible reservoirs of TPE strains. This could considerably complicate recent efforts to eradicate yaws. Genetic differences specific for Fribourg-Blanc could then contribute for identification of cases of animal-derived yaws infections.

A bacterial strain isolated in 1966 from baboons (Papio cynocephalus) in West Africa was preliminarily characterized as unclassified simian strain Treponema Fribourg-Blanc (FB). This strain was morphologically identical to T. pallidum ssp. pallidum (TPA, agent of syphilis) or ssp. pertenue (TPE, agent of yaws). In this study, we completed a high quality whole genome sequence of simian isolate Treponema Fribourg-Blanc and compared it to known genome sequences of Treponema pallidum strains. No major differences in the gene order of the FB genome were found when compared to all known genomes of Treponema pallidum subspecies. Moreover, the FB genome clustered with other TPE strains, while T. pallidum ssp. pallidum strains clustered separately. In general, the FB genome showed similar genetic characteristics to other TPE strains. Therefore, we proposed that the simian isolate Fribourg-Blanc be classified as a bacterial strain belonging to Treponema pallidum ssp. pertenue. It appears that, except for humans, the reservoir of yaws-causing treponemes may also include free-living primates, especially in Africa.

Treponema pallidum infection in the wild baboons of East Africa: distribution and genetic characterization of the strains responsible

It has been known for decades that wild baboons are naturally infected with Treponema pallidum, the bacterium that causes the diseases syphilis (subsp. pallidum), yaws (subsp. pertenue), and bejel (subsp. endemicum) in humans. Recently, a form of T. pallidum infection associated with severe genital lesions has been described in wild baboons at Lake Manyara National Park in Tanzania. In this study, we investigated ten additional sites in Tanzania and Kenya using a combination of macroscopic observation and serology, in order to determine whether the infection was present in each area. In addition, we obtained genetic sequence data from six polymorphic regions using T. pallidum strains collected from baboons at two different Tanzanian sites. We report that lesions consistent with T. pallidum infection were present at four of the five Tanzanian sites examined, and serology was used to confirm treponemal infection at three of these. By contrast, no signs of treponemal infection were observed at the six Kenyan sites, and serology indicated T. pallidum was present at only one of them. A survey of sexually mature baboons at Lake Manyara National Park in 2006 carried out as part of this study indicated that roughly ten percent displayed T. pallidum-associated lesions severe enough to cause major structural damage to the genitalia. Finally, we found that T. pallidum strains from Lake Manyara National Park and Serengeti National Park were genetically distinct, and a phylogeny suggested that baboon strains may have diverged prior to the clade containing human strains. We conclude that T. pallidum infection associated with genital lesions appears to be common in the wild baboons of the regions studied in Tanzania. Further study is needed to elucidate the infection's transmission mode, its associated morbidity and mortality, and the relationship between baboon and human strains.

Comparative investigation of the genomic regions involved in antigenic variation of the TprK antigen among treponemal species, subspecies, and strains

Although the three Treponema pallidum subspecies (T. pallidum subsp. pallidum, T. pallidum subsp. pertenue, and T. pallidum subsp. endemicum), Treponema paraluiscuniculi, and the unclassified Fribourg-Blanc treponeme cause clinically distinct diseases, these pathogens are genetically and antigenically highly related and are able to cause persistent infection. Recent evidence suggests that the putative surface-exposed variable antigen TprK plays an important role in both treponemal immune evasion and persistence. tprK heterogeneity is generated by nonreciprocal gene conversion between the tprK expression site and donor sites. Although each of the above-mentioned species and subspecies has a functional tprK antigenic variation system, it is still unclear why the level of expression and the rate at which tprK diversifies during infection can differ significantly among isolates. To identify genomic differences that might affect the generation and expression of TprK variants among these pathogens, we performed comparative sequence analysis of the donor sites, as well as the tprK expression sites, among eight T. pallidum subsp. pallidum isolates (Nichols Gen, Nichols Sea, Chicago, Sea81-4, Dal-1, Street14, UW104, and UW126), three T. pallidum subsp. pertenue isolates (Gauthier, CDC2, and Samoa D), one T. pallidum subsp. endemicum isolate (Iraq B), the unclassified Fribourg-Blanc isolate, and the Cuniculi A strain of T. paraluiscuniculi. Synteny and sequence conservation, as well as deletions and insertions, were found in the regions harboring the donor sites. These data suggest that the tprK recombination system is harbored within dynamic genomic regions and that genomic differences might be an important key to explain discrepancies in generation and expression of tprK variants among these Treponema isolates.

Genetic diversity in Treponema pallidum: implications for pathogenesis, evolution and molecular diagnostics of syphilis and yaws

Pathogenic uncultivable treponemes, similar to syphilis-causing Treponema pallidum subspecies pallidum, include T. pallidum ssp. pertenue, T. pallidum ssp. endemicum and Treponema carateum, which cause yaws, bejel and pinta, respectively. Genetic analyses of these pathogens revealed striking similarity among these bacteria and also a high degree of similarity to the rabbit pathogen, Treponema paraluiscuniculi, a treponeme not infectious to humans. Genome comparisons between pallidum and non-pallidum treponemes revealed genes with potential involvement in human infectivity, whereas comparisons between pallidum and pertenue treponemes identified genes possibly involved in the high invasivity of syphilis treponemes. Genetic variability within syphilis strains is considered as the basis of syphilis molecular epidemiology with potential to detect more virulent strains, whereas genetic variability within a single strain is related to its ability to elude the immune system of the host. Genome analyses also shed light on treponemal evolution and on chromosomal targets for molecular diagnostics of treponemal infections.

Whole genome sequences of three Treponema pallidum ssp. pertenue strains: yaws and syphilis treponemes differ in less than 0.2% of the genome sequence

Background

The yaws treponemes, Treponema pallidum ssp. pertenue (TPE) strains, are closely related to syphilis causing strains of Treponema pallidum ssp. pallidum (TPA). Both yaws and syphilis are distinguished on the basis of epidemiological characteristics, clinical symptoms, and several genetic signatures of the corresponding causative agents.

Methodology/Principal Findings

To precisely define genetic differences between TPA and TPE, high-quality whole genome sequences of three TPE strains (Samoa D, CDC-2, Gauthier) were determined using next-generation sequencing techniques. TPE genome sequences were compared to four genomes of TPA strains (Nichols, DAL-1, SS14, Chicago). The genome structure was identical in all three TPE strains with similar length ranging between 1,139,330 bp and 1,139,744 bp. No major genome rearrangements were found when compared to the four TPA genomes. The whole genome nucleotide divergence (d_A) between TPA and TPE subspecies was 4.7 and 4.8 times higher than the observed nucleotide diversity (π) among TPA and TPE strains, respectively, corresponding to 99.8% identity between TPA and TPE genomes. A set of 97 (9.9%) TPE genes encoded proteins containing two or more amino acid replacements or other major sequence changes. The TPE divergent genes were mostly from the group encoding potential virulence factors and genes encoding proteins with unknown function.

Conclusions/Significance

Hypothetical genes, with genetic differences, consistently found between TPE and TPA strains are candidates for syphilitic treponemes virulence factors. Seventeen TPE genes were predicted under positive selection, and eleven of them coded either for predicted exported proteins or membrane proteins suggesting their possible association with the cell surface. Sequence changes between TPE and TPA strains and changes specific to individual strains represent suitable targets for subspecies- and strain-specific molecular diagnostics.

Spirochete Treponema pallidum ssp. pertenue (TPE) is the causative agent of yaws while strains of Treponema pallidum ssp. pallidum (TPA) cause syphilis. Both yaws and syphilis are distinguished on the basis of epidemiological characteristics and clinical symptoms. Neither treponeme can reproduce outside the host organism, which precludes the use of standard molecular biology techniques used to study cultivable pathogens. In this study, we determined high quality whole genome sequences of TPE strains and compared them to known genetic information for T. pallidum ssp. pallidum strains. The genome structure was identical in all three TPE strains and also between TPA and TPE strains. The TPE genome length ranged between 1,139,330 bp and 1,139,744 bp. The overall sequence identity between TPA and TPE genomes was 99.8%, indicating that the two pathogens are extremely closely related. A set of 34 TPE genes (3.5%) encoded proteins containing six or more amino acid replacements or other major sequence changes. These genes more often belonged to the group of genes with predicted virulence and unknown functions suggesting their involvement in infection differences between yaws and syphilis.

Genome analysis of Treponema pallidum subsp. pallidum and subsp. pertenue strains: most of the genetic differences are localized in six regions

The genomes of eight treponemes including T. p. pallidum strains (Nichols, SS14, DAL-1 and Mexico A), T. p. pertenue strains (Samoa D, CDC-2 and Gauthier), and the Fribourg-Blanc isolate, were amplified in 133 overlapping amplicons, and the restriction patterns of these fragments were compared. The approximate sizes of the genomes investigated based on this whole genome fingerprinting (WGF) analysis ranged from 1139.3-1140.4 kb, with the estimated genome sequence identity of 99.57-99.98% in the homologous genome regions. Restriction target site analysis, detecting the presence of 1773 individual restriction sites found in the reference Nichols genome, revealed a high genome structure similarity of all strains. The unclassified simian Fribourg-Blanc isolate was more closely related to T. p. pertenue than to T. p. pallidum strains. Most of the genetic differences between T. p. pallidum and T. p. pertenue strains were accumulated in six genomic regions. These genome differences likely contribute to the observed differences in pathogenicity between T. p. pallidum and T. p. pertenue strains. These regions of sequence divergence could be used for the molecular detection and discrimination of syphilis and yaws strains.

On the origin of the treponematoses: a phylogenetic approach

Background

Since the first recorded epidemic of syphilis in 1495, controversy has surrounded the origins of the bacterium Treponema pallidum subsp. pallidum and its relationship to the pathogens responsible for the other treponemal diseases: yaws, endemic syphilis, and pinta. Some researchers have argued that the syphilis-causing bacterium, or its progenitor, was brought from the New World to Europe by Christopher Columbus and his men, while others maintain that the treponematoses, including syphilis, have a much longer history on the European continent.

Methodology/Principal Findings

We applied phylogenetics to this problem, using data from 21 genetic regions examined in 26 geographically disparate strains of pathogenic Treponema. Of all the strains examined, the venereal syphilis-causing strains originated most recently and were more closely related to yaws-causing strains from South America than to other non-venereal strains. Old World yaws-causing strains occupied a basal position on the tree, indicating that they arose first in human history, and a simian strain of T. pallidum was found to be indistinguishable from them.

Conclusions/Significance

Our results lend support to the Columbian theory of syphilis's origin while suggesting that the non-sexually transmitted subspecies arose earlier in the Old World. This study represents the first attempt to address the problem of the origin of syphilis using molecular genetics, as well as the first source of information regarding the genetic make-up of non-venereal strains from the Western hemisphere.

For 500 years, controversy has raged around the origin of T. pallidum subsp. pallidum, the bacterium responsible for syphilis. Did Christopher Columbus and his men introduce this pathogen into Renaissance Europe, after contracting it during their voyage to the New World? Or does syphilis have a much older history in the Old World? This paper represents the first attempt to use a phylogenetic approach to solve this question. In addition, it clarifies the evolutionary relationships between the pathogen that causes syphilis and the other T. pallidum subspecies, which cause the neglected tropical diseases yaws and endemic syphilis. Using a collection of pathogenic Treponema strains that is unprecedented in size, we show that yaws appears to be an ancient infection in humans while venereal syphilis arose relatively recently in human history. In addition, the closest relatives of syphilis-causing strains identified in this study were found in South America, providing support for the Columbian theory of syphilis's origin.

Molecular differentiation of Treponema pallidum subspecies

Treponema pallidum includes three subspecies of antigenically highly related treponemes. These organisms cause clinically distinct diseases and cannot be distinguished by any existing test. In this report, genetic signatures are identified in two tpr genes which, in combination with the previously published signature in the 5' flanking region of the tpp15 gene, can differentiate the T. pallidum subspecies, as well as a simian treponeme.

Early yaws, imported in The Netherlands

Early yaws in a 9 year old girl from Ghana, diagnosed as imported disease in The Netherlands is reported. She had lived in The Netherlands for six months. Tropical non-venereal treponematoses are rarely seen in Europe, and only a few case reports have been published. Migration and travelling may confront the medical profession with cases of tropical diseases such as yaws. Positive serological reactions in non-venereal tropical or venereal treponematoses cannot be distinguished at present.

Changing patterns of treponemal disease

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