Molecular Epidemiology and Cross-Border Transmission of Leprosy in the SeneGambia

Leprosy, caused by M. leprae, remains a major health concern, leading to severe deformities and disabilities if diagnosed late (Finardi et al., 2023). Despite control efforts, about 200,000 new cases are reported annually, with stable notification rates over the past two decades (WHO 2023a).
In Africa, the disease persists, with 21,043 new cases (11.5% of the global total) recorded in 2023 (WHO, 2024a). The Gambia and Senegal face common challenges, including under-detection, lack of molecular diagnostics, and absent drug resistance surveillance, although the NLTP in Senegal, supported by NGOs, has implemented control innovations not yet considered in The Gambia. Detection delays contribute to ongoing transmission and late-stage diagnoses with irreversible disabilities. Social factors, including stigma, and socioeconomic disparities, further hinder control efforts.
Mapping the spatial and genetic distribution of M. leprae genotypes and enhancing molecular diagnostic capacity are crucial to addressing these challenges. The WHO’s Leprosy Elimination Monitoring Tool (LEMT) has proven effective in targeting interventions at sub-national levels but has yet to be implemented in The Gambia, its application to programmatic data can provide critical insights into spatial epidemiology. Senegal's application of similar tools has helped identify leprosy hotspots.
This proposed project aims to test a novel approach in intermediate incidence level settings: by identifying the spatio-epidemiological distribution of patients’ M. leprae genotypes in a cohort study conducted with both NLTPs, we will highlight areas and key populations where innovative leprosy control measures will be most efficient and effective. This highly transdisciplinary project will involve social scientists and people affected by leprosy and build local capacity for molecular diagnostics and address gaps in molecular epidemiology and drug resistance surveillance to improve leprosy control in both countries. Embedded in the research, capacity strengthening is an important objective, with the NLTP in The Gambia seeking guidance on their National Strategic Plan from the Senegalese NLTP, and assistance in facilitating a civil society organisation of people affected by leprosy, already in place in Senegal.