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Outbreaks of yaws-like ulcerative skin lesions in children are frequently reported in tropical and sub-tropical countries. The origin of these lesions might be primarily traumatic or infectious; in the latter case, Treponema pallidum subspecies pertenue , the yaws agent, and Haemophilus ducreyi , the agent of chancroid, are two of the pathogens commonly associated with the aetiology of skin ulcers. In this work, we investigated the presence of T . p . pertenue and H . ducreyi DNA in skin ulcers in children living in yaws-endemic regions in Cameroon. Skin lesion swabs were collected from children presenting with yaws-suspected skin lesions during three outbreaks, two of which occurred in 2017 and one in 2019. DNA extracted from the swabs was used to amplify three target genes: the human β 2 -microglobulin gene to confirm proper sample collection and DNA extraction, the polA gene, highly conserved among all subspecies of T . pallidum , and the hddA gene of H . ducreyi . A fourth target, the tprL gene was used to differentiate T . p . pertenue from the other agents of human treponematoses in polA -positive samples. A total of 112 samples were analysed in this study. One sample, negative for β 2 -microglobulin, was excluded from further analysis. T . p . pertenue was only detected in the samples collected during the first 2017 outbreak (12/74, 16.2%). In contrast, H . ducreyi DNA could be amplified from samples from all three outbreaks (outbreak 1: 27/74, 36.5%; outbreak 2: 17/24, 70.8%; outbreak 3: 11/13, 84.6%). Our results show that H . ducreyi was more frequently associated to skin lesions in the examined children than T . p . pertenue , but also that yaws is still present in Cameroon. These findings strongly advocate for a continuous effort to determine the aetiology of ulcerative skin lesions during these recurring outbreaks, and to inform the planned mass treatment campaigns to eliminate yaws in Cameroon.

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.

Epidemics of yaws-like cutaneous ulcers are regularly documented in children in the tropics. They occur mainly in poor and remote communities without access to health facilities. The integration of molecular tools into yaws control efforts has made it possible to describe Haemophilus ducreyi ( HD ) as a major cause of cutaneous ulcers. The objective of this study was to determine the prevalence of HD as cause of cutaneous ulcers, investigate its presence in asymptomatic individuals and identify associated risk factors. A cross-sectional study was conducted in yaws endemic districts of Cameroon. Participants included people presenting yaws-like ulcers and asymptomatic individuals. Swab samples were collected from each participant and tested for HD and Treponema pallidum ( TP ) using an established qPCR method. Additionally, demographic, habitat, proximity, and hygiene characteristics were collected using a structured questionnaire. A total of 443 individuals participated in the study, including 271 ulcer cases and 172 asymptomatic contacts. The prevalence of HD in ulcers was 30.3% (Confidence Interval (CI) 95% [24.8–35.7]) and the prevalence of asymptomatic HD carriage was 8.6% (CI95% [4.5–12.9]). TP was also detected in our sample among ulcer cases but in lower proportion (5.2% CI95% [2.5–7.8]) compared to HD . The adjusted logistic regression model showed that women were as much at risk of having HD cutaneous ulcer as men regardless of age. Physical proximity to a confirmed ulcer case was the major factor identified favouring HD transmission. HD ulcers were more likely to be present on Bantu individuals compared to Baka as well as HD colonization. These findings highlight HD as the most common cause of cutaneous ulcers in yaws-endemic communities in Cameroon. The exact implications of detecting HD on intact skin are not yet clear. Further studies are needed to understand the significance of this carriage in the spread dynamics of the disease.

We aimed to establish an external quality assessment (EQA) programme for the yaws eradication campaign that would meet the needs of reference and district-level laboratories in low- and middle-income countries. We designed proficiency testing items (PTIs) using a plasmid containing gene target sequences for Treponema pallidum (TP) and Haemophilus ducreyi (HD). The storage stability of the plasmids under different environmental conditions was then tested. A proficiency testing panel of seven swabs loaded with different concentrations of plasmids in different combinations, as well as human HEK293 cells to simulate the sample background, was prepared and sent to participating reference (RL) and district (DL) laboratories in Ghana, Côte d'Ivoire and Cameroon followed by three rounds of blinded proficiency testing. We tested quantitative real-time PCR (qPCR) performance of reference laboratories and loop-mediated isothermal amplification (LAMP) performance of district laboratories and retested 20% of human field samples at the London School of Hygiene & Tropical Medicine laboratories to further assess qPCR quality. PTIs proved to be stable in dry conditions with no significant loss of copy number. Participating laboratories achieved qPCR results with a concordance of 95.0-100.0% (97.7% ± 5.2% (mean±standard deviation ((SD)) with the provider and a concordance of 76.0-100.0% (TP: 90.3 ± 13.7% and HD: 78.5 ± 7.5% (mean±SD)) for LAMP results, with inconsistencies, particularly in the detection of low HD plasmid DNA levels combined with high TP plasmid copies. Retesting of field samples resulted in 100% correct TP and HD sample identification by the African reference laboratories. We have developed a functional plasmid-based EQA programme specifically designed to meet the needs of resource-poor settings in the tropics. The programme is suitable as a blueprint for other disease programmes.

Integrated approaches to mapping skin Neglected Tropical Diseases (NTDs) may be cost-effective way to guide decisions on resource mobilization. Pilot studies have been carried out, but large-scale data covering multiple countries endemic for skin NTDs are lacking. Within the LAMP4YAWS project, we collected integrated data on the burden of multiple skin NTDs. From March 2021 to March 2023, integrated case searches for yaws alongside other skin conditions were performed in endemic health districts of yaws in Cameroon, Côte d'Ivoire, and Ghana. Integrated activities included training, social mobilization and active case detection. Initial screening involved a brief clinical examination of participants to determine if any skin conditions were suspected. Cases of skin NTDs were then referred to a health facility for appropriate management. Overall 61,080 individuals screened, 11,387 (18.6%) had skin lesions. The majority of individuals (>90%) examined were children aged 15 years old and under. The proportion of serologically confirmed yaws cases was 8.6% (18/210) in Cameroon, 6.8% (84/1232) in Côte d'Ivoire, and 26.8% (440/1643) in Ghana. Other skin conditions based on clinical examination included: scabies, Buruli ulcer, leprosy, lymphatic filariasis (lymphoedema and hydrocele), tungiasis, and fungal infections. The most common conditions were scabies and superficial fungal infections. In Cameroon, scabies and superficial fungal infections accounted for 5.1% (214/4204) and 88.7% (3730/4204) respectively, 25.2% (1285/5095) and 50.4% (2567/5095) in Côte d'Ivoire. In Ghana, 20% (419/2090) of individuals had scabies but superficial fungal infections were not routinely recorded and were reported in only 1.3% (28/2090). Other skin NTDs were less common across all three countries. This study confirms that integrated screening allows simultaneous detection of multiple skin NTDs, maximising use of scarce resources.

Yaws, caused by Treponema pallidum ssp. pertenue , remains a significant public health concern in tropical regions of West Africa and the South Pacific, primarily affecting children in remote areas with limited access to hygiene and sanitation. In this study, conducted in three endemic countries of West Africa where yaws remains a significant public health concern (Ghana, Cameroon, and Côte d’Ivoire), we aimed to assess the knowledge, attitudes, and practices related to yaws among community members, community health workers (CHWs), and traditional healers. The study revealed variations in the perception of causes of yaws among community members: the majority or participants in Ghana attributed yaws to germs (60.2%); in Cameroon the most reported form of transmission was contact with or drinking infected water sources (44.6%); and in Côte d’Ivoire both of these answers were also the most prevalent (60.3% germs and 93.% water sources). A substantial proportion of participants in Côte d’Ivoire also associated yaws with witchcraft and divine punishment (44.8%). Only a small proportion of individuals in Ghana and Côte d’Ivoire correctly identified contact with an infected person as a form of transmission (11.9% and 20.7%, respectively) and less than half in Cameroon (42.6%), although more than 98% of all participants reported avoidance behaviours towards yaws infected people due to fear of getting infected. Most participants expressed a preference for seeking care at hospitals (49.2%, 60.6%, 86.2%) or health care professionals including doctors and nurses (58.5%, 41,5% and 17.2%) if they were diagnosed with yaws, although a quarter of participants in Côte d’Ivoire also sought support from traditional healers. The CHWs interviewed were generally well-trained on yaws causes and treatment options, although they often reported low availability of treatment and diagnostic tests for yaws. Our findings underscore the need for community education, awareness campaigns, ongoing CHW training, and improved access to yaws treatment and diagnostic resources. The data also suggest that collaboration with traditional healers, who usually hold a highly esteemed position in the society, such as giving training on yaws causes and transmission or exchanging knowledge on treatment options, could be beneficial in certain regions, particularly in Côte d’Ivoire.