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This document provides a summary of guidance developed for national programmes on conducting serosurveys to assess yaws transmission status, with the objective of confirming yaws seroprevalence below 1% at each of three serosurveys over a period of 3–10 years after reporting the last case of active yaws in a region. It proposes active testing of children aged 1–5 years through population-based surveys and includes recommendations on survey design, sample size determination, sampling of primary sampling units (PSUs) within an evaluation unit, sampling of households within PSUs, integration with existing public health surveys, and follow-up protocols for positive results. Geospatial analysis and sustained surveillance are recommended for accurate assessment of whether transmission interruption has been achieved.

Treponema pallidum subspecies pertenue (TPE) is the causative agent of human and nonhuman primate (NHP) yaws infection. The discovery of yaws bacterium in wild populations of NHPs opened the question of transmission mechanisms within NHPs, and this work aims to take a closer look at the transmission of the disease. Our study determined eleven whole TPE genomes from NHP isolates collected from three national parks in Tanzania: Lake Manyara National Park (NP), Serengeti NP, and Ruaha NP. The bacteria were isolated from four species of NHPs: Chlorocebus pygerythrus (vervet monkey), Cercopithecus mitis (blue monkey), Papio anubis (olive baboon), and Papio cynocephalus (yellow baboon). Combined with previously generated genomes of TPE originating from NHPs in Tanzania (n = 11), 22 whole-genome TPE sequences have now been analyzed. Out of 231 possible combinations of genome-to-genome comparisons, five revealed an unexpectedly high degree of genetic similarity in samples collected from different NHP species, consistent with inter-species transmission of TPE among NHPs. We estimated a substitution rate of TPE of NHP origin, ranging between 1.77 × 10-7 and 3.43 × 10-7 per genomic site per year. The model estimations predicted that the inter-species transmission happened recently, within decades, roughly in an order of magnitude shorter time compared to time needed for the natural diversification of all tested TPE of Tanzanian NHP origin. Moreover, the geographical separation of the sampling sites (NPs) does not preclude TPE transmission between and within NHP species.

Children in parts of Africa, the South Pacific, and Southeast Asia frequently develop cutaneous ulcers caused by two bacteria: Haemophilus ducreyi (HD) and Treponema pallidum subspecies pertenue (causative agent of yaws). The World Health Organization (WHO) aims to eradicate yaws using mass administration of azithromycin. This also leads to a temporary decrease in ulcers caused by HD followed by a rebound suggesting an ongoing reservoir of infection. The aim of this study was to investigate whether HD could spread through the environment or animals. Alongside detection of human cases of cutaneous ulcers from villages in Cameroon, we additionally collected samples from animals (dogs, cats, flies), fomites (bedsheets, clothing, benches, doors), and water sources (marigots and lakes). DNA was extracted and tested for HD and T. pallidum using two specific qPCR assays. HD was not detected in any of the environmental samples but it was on both clothing (13.3%) and in flies (27%). Flies also tested positive for T. pallidum, but at a lower rate (2.6%). These results suggest that flies and some fomites may contribute to the transmission of HD. Future research should focus on determining whether either of these are capable of carrying live bacteria that can cause onward transmission.

Background Yaws is a chronic relapsing disease caused by Treponema pallidum subspecies pertunue , which can result in severe disability and deformities. Children below the age of 15 years in resource-poor communities are the most affected. Several non-specific factors facilitate the continuous transmission and resurgence of the disease. Endemic communities in rural Ghana continue to report cases despite the roll out of several intervention strategies in the past years. The objective of this study was to determine the factors associated with cutaneous ulcers among children in two yaws-endemic districts in Ghana. Methods A community-based unmatched 1:2 case-control study was conducted among children between 1 and 15 years. Data on socio-demographic, environmental and behavioral factors were collected using a structured questionnaire. Active case search and confirmation was done using the Dual Path Platform (DPP) Syphilis Screen and Confirm test kit. Data were analyzed using STATA 15. Logistic regression was done to determine the exposures that were associated with yaws infection at 0.05 significant level. Results Sixty-two cases and 124 controls were recruited for the study. The adjusted multivariable logistic regression model showed that yaws infection was more likely among individuals who reside in overcrowded compound houses (a OR  = 25.42, 95% CI: 6.15–105.09) and with poor handwashing habits (a OR  = 6.46, 95% CI: 1.89–22.04). Male (a OR  = 4.15, 95% CI: 1.29–13.36) and increasing age (a OR  = 5.90, 95% CI: 1.97–17.67) were also associated with yaws infection. Conclusions Poor personal hygiene, overcrowding and lack of access to improved sanitary facilities are the factors that facilitate the transmission of yaws in the Awutu Senya West and Upper West Akyem districts. Yaws was also more common among males and school-aged children. Improving living conditions, access to good sanitary facilities and encouraging good personal hygiene practices should be core features of eradication programs in endemic communities.

In the global program for the eradication of yaws, assessments of the prevalence of the disease are used to decide where to initiate mass treatment. However, the smallest administrative unit that should be used as the basis for making decisions is not clear. We investigated spatial and temporal clustering of yaws to help inform the choice of implementation unit. We analyzed 11 years of passive surveillance data on incident yaws cases (n = 1448) from Lihir Island, Papua New Guinea. After adjusting for age, sex, and trends in health-seeking, we detected three non-overlapping spatial-temporal clusters (p < 1 × 10(-17), p = 1.4 × 10(-14), p = 1.4 × 10(-8)). These lasted from 28 to 47 months in duration and each encompassed between 4 and 6 villages. We also assessed spatial clustering of prevalent yaws cases (n = 532) that had been detected in 7 biannual active case finding surveys beginning in 2013. We identified 1 statistically significant cluster in each survey. We considered the possibility that schools that serve multiple villages might be loci of transmission, but we found no evidence that incident cases of yaws among 8- to 14-year-olds clustered within primary school attendance areas (p = 0.6846). These clusters likely reflect transmission of yaws across village boundaries; villages may be epidemiologically linked to a degree such that mass drug administration may be more effectively implemented at a spatial scale larger than the individual village.

The search for new strategies and technologies for the control of yaws, a genuine but much neglected tropical disease problem, has been largely unsuccessful. This disease, with conspicuous early symptoms and a late crippling pathology, attracted the attention of the first generation of tropical doctors. As soon as specific therapy became available in the early part of the 20th century, mass treatment campaigns were started. The availability and efficacy of penicillin led some to anticipate yaws eradication; this expectation was not met but rather induced a false sense of security. After varying intervals resurgences occurred in several endemic regions. It is important to analyze this failure so that mistakes and underestimated or overlooked factors can be identified. On the whole, the main difficulty has been a lack of interest in a presumably disappearing disease and a consequent failure to take advantage of the benefits offered by recent advances in basic biomedical technology. Solid clinical, epidemiologic, and sociocultural data in connection with mass treatment and control are still needed. Research of high quality, with continuous assessment in the field, is a prerequisite for innovative strategies and technologies.

Previous mass campaigns against the endemic treponematoses have taught investigators several lessons that, along with current constraints and altered circumstances, must be considered in the formulation of a contemporary strategy for the control or eradication of yaws, endemic syphilis, or pinta. A time-limited, vertical approach is necessary in highly endemic areas initially to reduce the level of transmission. Elsewhere, control activities should be integrated into other primary health care interventions, especially health education, water and sanitation programs, maternal and child health care, and provision of essential drugs. Control of the endemic treponematoses is an ideal means of strengthening primary health care in endemic areas.

The elimination of yaws from large geographic areas provides evidence that global elimination of person-to-person yaws transmission is feasible. The failure to reach that goal to date is the result of managerial rather than technical deficiencies. If the eradication of yaws can be accomplished, it should be done to reduce the suffering that is associated with the disease. In addition, a positive benefit-cost ratio is likely to be realized within a period of decades, and in areas endemic for yaws, its elimination could well provide a basis for the development of a strong system of primary health care. The decision to eliminate yaws must be made deliberately by the World Health Assembly with full knowledge of the implication of not making such a decision. A positive decision would result in enriched lives for countless potential victims of yaws and save the world money in the long term.

The final results of a three-year campaign against yaws in the Republic of Ghana, which was introduced in an attempt to reduce an unusually high prevalence, are summarized. The campaign started in January 1981 and officially ended in December 1983. Serious economic and technical constraints slowed the progress of work after the first year and reduced the total population covered. In spite of the shortcomings, the program provided penicillin treatment to 77,818 patients with active yaws (4.04% of those examined during the campaign) as well as chemoprophylaxis for an additional 1,556,360 contacts. The campaign staff compiled detailed information on the epidemiology of yaws in Ghana. A second attack phase using simple equipment and vehicles such as motorcycles and bicycles could be implemented with greater efficiency and could reduce costs.