Integrated Mapping of Skin-presenting Neglected Tropical Diseases in Liberia

Innovative and intensified disease management (IDM) includes a range of different interventions - ranging from medicine to surgery - to relieve the symptoms and consequences of a group of neglected tropical diseases (NTDs) for which effective tools are scarce or where the widespread use of existing tools is limited. The World Health Organisation (WHO) has developed a series of strategies to achieve the control, elimination and eventual eradication of these NTDs, comprising universal access to early diagnosis and prompt treatment, improving active surveillance, integrating passive surveillance into health-service provision, and accelerating efforts towards elimination and eradication by intensifying core interventions. Appropriate targeting of IDM interventions requires accurate epidemiological data on the distribution of these NTDs within endemic countries. In most instances however, existing case register data generated through national health management information systems or during programmatic activities do not provide an accurate representation of the true burden of IDM NTDs.

A number of IDM NTDs are characterised by cutaneous manifestations that are associated with long-term disfigurement and disability. These include Buruli ulcer, cutaneous leishmaniasis, leprosy, mycetoma, yaws, onchocerciasis and lymphoedema and hydrocele (resulting from lymphatic filariasis and podoconiosis). These diseases require similar case-detection approaches, presenting opportunities for the development of novel, integrated mapping approaches. Population-based prevalence surveys (PBPS) are the gold standard methodology for obtaining accurate disease estimates when case detection and reporting through the health system is incomplete, and these have been used to provide sub-national estimates of disease distributions for yaws and podoconiosis. For less common outcomes (fewer than 1 case in 1000 individuals) however, standard PBPS rapidly become unfeasible. Given that the expected prevalence range for many of these IDM NTDs in endemic regions lies between as low as 1 in 10,000 for Buruli ulcer and 1-5% for yaws, it is clear that the PBPS approach requires adaptation to achieve the samples sizes needed to generate sufficiently precise prevalence estimates.

One alternative to randomly sampling individuals or households is to screen all residents within sampling clusters. House-to-house screening by mobile expert teams would likely yield the highest number of cases, but such a strategy would be expensive and difficult to sustain. As an alternative, trained village volunteers have been used during programmatic activities to effectively detect and refer diseases such as Buruli ulcer and leprosy in a number of countries. Given how difficult it is to diagnose many IDM-NTDs accurately, using community volunteers to perform an exhaustive house-to-house case search would require follow up expert case validation. The success of such an approach would thus rely on high levels of community awareness, coupled with well-trained village volunteers being able to recognise possible conditions, and a highly skilled, mobile case-validation team to confirm all potential cases. Effectively incorporating skill development in IDM-NTD screening among village volunteers could however represent a long-term and sustainable solution to the complex issue of managing these conditions at the community and primary health care level.

This study aims to establish the prevalence and distribution of case-management NTDs in the county of Maryland, Liberia using an integrated two-stage cluster-randomised sampling approach, including assessment of the proportion of cases not currently known to the health system.

The specific objectives include:

1. To generate regional prevalence estimates of (i) lymphatic filariasis-associated lymphoedema and hydrocele, (ii) yaws, (iii) Buruli ulcer and (iv) leprosy in Maryland, Liberia, including the proportion of cases not currently known to the health system
2. To model the endemicity status of (i) lymphoedema and hydrocele, (ii) yaws, (iii) Buruli ulcer and (iv) leprosy to support the development of targeted, integrated control strategies.
3. To compare case detection rates from active community-based screening and validation with passive case detection reported through routine health system reports and health management information systems.

This protocol represents a novel tool for integrated mapping of IDM-NTDs. These conditions are difficult to diagnose and lack effective tools for both case finding and disease management purposes. This strategy may provide a template for cost-effective case identification and management that can be integrated within routine health systems in similar epidemiological settings.