The WHO ‘Technical guidance on interruption of transmission and elimination of leprosy disease’ and its associated tools, ‘Leprosy Programme and Transmission Assessment Tool (LPTA) and ‘Leprosy Elimination Monitoring Tool (LEMT)’ were prepared following recommendations of the WHO Taskforce for defining cut-offs and criteria for verification of interruption of transmission and elimination of leprosy disease and a series of consultations with experts in leprosy and national programme managers.
Leprosy is one of the Neglected Tropical Diseases (NTDs) targeted for elimination (interruption of transmission) along with Onchocerciasis and Human African Trypanosomiasis according to Ending the neglect to attain the Sustainable Development Goals: A road map for neglected tropical diseases 2021–2030 (NTD Road map 2030).
A new Leprosy Elimination Framework has been defined with three phases followed eventually by a non-endemic status. The Leprosy Elimination Framework outlines the phases of elimination with indicators and milestones showing when an area or country moves from one phase to the next. Sub-national areas can be easily classified based on existing data and mapped to visualize how the country progresses towards the goals of interruption of transmission and elimination of leprosy. According to this framework, interruption of transmission is defined as an epidemiological state in a country/ area where there is no more local transmission of M. leprae, evidenced by zero new autochthonous case among children for at least five consecutive years. After this milestone, if no autochthonous cases (all ages) are reported for three consecutive years the sub-national jurisdiction or country is considered to have reached elimination of leprosy. The process of verification is essentially sub-national level upwards. Phase 3 is one of post-elimination surveillance wherein sporadic cases may still be reported owing to the long incubation period of leprosy.
The Leprosy Elimination Monitoring Tool (LEMT) is an Excel-based tool that allows areas and countries to monitor progress across the phases of elimination and determine when they (are ready to) move from one phase to the next.
The Leprosy Programme and Transmission Assessment (LPTA) can be used by ministries of health and leprosy programme managers to assess the status of the programme and related leprosy services with regard to a set of programme criteria that comprehensively cover all key aspects of a leprosy programme. This may be done before a sub-national level area is to be acknowledged by the health ministry for having achieved interruption of transmission and/or elimination of leprosy but could be used at other times also. Importantly, this tool would be used at the national level by WHO to verify that a country has indeed reached the milestone of elimination of leprosy disease.
The guidance recommends critical actions to be taken by Member countries and the LPTA and LEMT support programme managers to garner and document evidence in order to prepare a dossier for verification of elimination of leprosy disease.
The disease
Leprosy is caused by infection with the bacillus Mycobacterium leprae, which multiplies very slowly in the human body. The bacterium has a long incubation period (on average 5 years or longer). The disease affects nerve endings and destroys the body’s ability to feel pain and injury.
Leprosy is curable. Treatment provided in the early stages of infection averts disability. Multidrug therapy is available free of charge through WHO. This therapy has been donated by The Nippon Foundation in the past (1995–2000), and by Novartis since 2000, with an agreement to continue until at least 2025.
Continued discrimination has deterred people from coming forward for diagnosis and treatment – thus encouraging cases to remain hidden and indirectly contributing to transmission.
Social stigma also facilitates transmission among vulnerable groups, including migrant populations, displaced communities, and very poor and hard-to-reach populations. Combating stigma and achieving early diagnosis through active, early case-finding are critical to interrupting transmission.