WASH Exposure and Animal Interfaces Reappear Across Skin Neglected Tropical Diseases
A scoping review in skin neglected tropical diseases has pulled together a scattered body of evidence linking water, sanitation, hygiene, and broader One Health exposures to disease risk. The review mapped primary studies across the 12 WHO-recognised skin NTDs and found a literature that is both informative and strikingly incomplete: only 30 studies from 17 countries met inclusion criteria, and most of the evidence clustered around just three conditions. Buruli ulcer accounted for 10 studies, cutaneous leishmaniasis for 9, and tungiasis for 7. Four WHO-recognised skin NTDs — onchocerciasis, yaws, chromoblastomycosis, and sporotrichosis — had no studies at all.
The pattern matters because these diseases sit at the intersection of poverty, infrastructure, environment, and animal exposure. Skin NTDs often emerge where people live with limited access to safe water, basic sanitation, durable housing, and vector or reservoir control. In that setting, the review does not just catalogue associations; it points to repeated biological and ecological pathways that help explain why some communities carry a heavier burden than others.
Improved water access emerged as protective for Buruli ulcer and cutaneous leishmaniasis. Poor housing showed a consistent association with tungiasis, with adjusted odds ratios ranging from 3.35 to 5.83. Those findings are clinically intuitive and epidemiologically important. Inadequate housing can increase contact with soil, vectors, and domestic environments where flea infestation or arthropod exposure is more likely, while reliable water access can reduce both environmental contamination and the need for risky water-contact behaviors. The review’s signal is not that one intervention solves everything, but that the basic infrastructure often sits upstream of multiple pathways at once.
One sentence captures the practical consequence: the home itself can be a vector of disease risk.
Environmental and Reservoir Signals Extend Beyond Water Alone
The review’s One Health findings move the discussion beyond classic WASH metrics. Possum density showed dose-response associations with Buruli ulcer, with adjusted odds ratios between 4.52 and 6.06. Animal proximity, including contact with domestic animals and wildlife reservoirs, was associated with cutaneous leishmaniasis, with adjusted odds ratios from 2.4 to 3.12. Those findings support a broader transmission frame in which animal hosts, environmental contamination, and human behavior interact rather than operate in isolation.
The detection of Mycobacterium ulcerans DNA and viable Mycobacterium leprae mRNA in community water sources is especially notable, even though direct transmission to humans was not established. Detection in water does not prove infection, and the review does not claim that it does. Still, the microbiologic findings strengthen the plausibility of environmental persistence and underscore why water systems deserve attention even when the route from reservoir to human disease remains unresolved. Environmental sampling can identify where organisms are present; proving causality requires much more than molecular detection alone.
This is where the One Health frame becomes more than a slogan. When disease ecology includes reservoirs, vectors, domestic animals, wildlife, and contaminated environments, prevention cannot stop at household behavior. Housing quality, land use, animal exposure, and community water sources all become part of the same risk network.
A Thin Interventional Evidence Base Leaves Prevention Policy Underpowered
Only one interventional study was identified. That single detail should give policymakers pause. Observational associations can identify risk markers and suggest plausible mechanisms, but they do not establish which package of environmental, behavioral, or animal-interface interventions will reliably reduce incidence in real communities.
The review searched MEDLINE/PubMed from inception through November 2025 and followed PRISMA-ScR methods, with inclusion limited to English-language primary studies that assessed at least one skin NTD, one WASH domain, and one One Health dimension. The resulting map is rigorous in method, yet the evidence itself remains narrow. Geographic coverage was uneven, and the literature remained concentrated largely in Africa. Even with 17 countries represented, the distribution of studies was not broad enough to support confident global generalization across all endemic settings.
This concentration has clinical and programmatic consequences. If the strongest data come from a few diseases and a few regions, then integrated WASH and One Health strategies risk being designed around incomplete transmission profiles. Buruli ulcer, cutaneous leishmaniasis, and tungiasis may receive most of the analytic attention, while other skin NTDs remain effectively invisible in the evidence base. For endemic communities facing multiple simultaneous exposures, invisibility at the study level often translates into weak prioritization at the policy level.
The WHO 2030 Roadmap calls for integrated approaches, and this review shows why that call is necessary. Water access, environmental sanitation, housing quality, and animal-interface management repeatedly appear as protective or risk-associated factors. Yet the field still lacks enough intervention research to answer a basic implementation question: which combination of infrastructure and exposure-control measures produces the largest and most durable reduction in disease?
For now, the evidence supports a cautious but concrete reading. Better water access appears protective in some skin NTDs. Poor housing is repeatedly linked to tungiasis. Animal and environmental reservoirs matter for Buruli ulcer and cutaneous leishmaniasis. And the absence of studies for four WHO-recognised skin NTDs leaves major blind spots in global prevention planning.
The next step is not another broad statement of need. It is a larger interventional literature that tests integrated WASH and One Health packages across underrepresented diseases, underrepresented regions, and real community settings where transmission actually occurs.