Interrupting transmission of Mycobacterium leprae: synthesis of new evidence and research recommendations

On May 23–25, 2024, a multidisciplinary expert group met in Bergen, Norway, the site of the first description of Mycobacterium leprae (M. leprae) in 1873, to discuss advancements and remaining knowledge gaps in the transmission of M. leprae at the Global Partnership for Zero Leprosy Zero Transmission Symposium. Research and operational approaches to interruption of transmission were identified; the research approaches from the symposium are described here. Updates since a previous symposium at the National School of Tropical Medicine, Baylor College of Medicine in Houston (USA), in 2014 from these fields of research are presented here: epidemiology; microbiological diagnosis; immunodiagnostics; genotyping; geospatial mapping; leprosy elimination monitoring and transmission under low-endemic circumstances; leprosy post-exposure prophylaxis (PEP); modelling relevant to interruption of transmission of M. leprae; OneHealth; environmental transmission of M. leprae; social determinants; control programmes relevant to interruption of transmission of M. leprae; and organizations of persons affected. Progress and outstanding gaps since 2014 are identified, and recommendations for relevant research in these areas to achieve interruption of transmission are presented. These include research into human reservoirs, including platforms for field-friendly diagnostics; routes of entry/exit of M. leprae; the roles of animals or vectors in transmission; the role of social determinants in transmission; host-pathogen interactions; transmission networks; and enhanced epidemiological data. Fulfilment of these research recommendations and further understanding of which settings require intensified control efforts, will help to advance the aim of achieving complete interruption of transmission of M. leprae and the elimination of leprosy disease.