Leprosy on Anjouan (Comoros): persistent hyper-endemicity despite decades of solid control efforts

Introduction: Despite decades of solid leprosy control efforts, the disease remains highly endemic on the island of Anjouan, Comoros. Among a population of less than 400,000 over 300 new leprosy patients are diagnosed on average annually.

Methods: We analysed routine data for the period of 2000-2015 for trends in epidemiological parameters and clustering in time and space.

Results: Leprosy incidence remains high (7.4/10,000 per year, on average) with no indications of an imminent decrease. Increasing coverage of active case finding has led to increasing numbers of leprosy patients being detected over the past 8 years. The proportion of new patients presenting with visible deformities has consistently been low (2.4% on average). The proportion of children among new patients exceeds 30%, without any trend towards a decrease. At macro-level clusters in time and space were observed scattered across the island, without a clear pattern.

Discussion: The leprosy epidemic on Anjouan continues unabated despite the activities of a well-organised control programme. There appears to be a need to further scale up case finding efforts and organise them in a more systematic manner. Use of modern technology, such as Geographic Information Systems, could help to improve targeting of case finding efforts. Prophylactic treatment of contacts should be considered. Studying markers of infection such as anti PGL-1, and DNA finger printing of leprosy bacteria could provide insights in the patterns of transmission and could be useful in identifying those at higher risk of developing leprosy for prophylactic treatment.