Overview
Leprosy is an age-old disease and is described in the literature of ancient civilizations. It is a chronic infectious disease which is caused by a type of bacteria called Mycobacterium leprae. The disease affects the skin, the peripheral nerves, mucosa of the upper respiratory tract, and the eyes. Leprosy is curable and treatment in the early stages can prevent disability. Apart from the physical deformity, persons affected by leprosy also face stigmatization and discrimination.
Scope of the problem
Leprosy is a neglected tropical disease (NTD) which still occurs in more than 120 countries, with more than 200 000 new cases reported every year. Elimination of leprosy as a public health problem globally (defined as prevalence of less than 1 per 10 000 population) was achieved in 2000 (as per World Health Assembly resolution 44.9) and in most countries by 2010. The reduction in the number of new cases has been gradual, both globally and in the WHO regions. As per data of 2019, Brazil, India and Indonesia reported more than 10 000 new cases, while 13 other countries (Bangladesh, Democratic Republic of the Congo, Ethiopia, Madagascar, Mozambique, Myanmar, Nepal, Nigeria, Philippines, Somalia, South Sudan, Sri Lanka and the United Republic of Tanzania) each reported 1000–10 000 new cases. Forty-five countries reported 0 cases and 99 reported fewer than 1000 new cases.
Transmission
The disease is transmitted through droplets from the nose and mouth. Prolonged, close contact over months with someone with untreated leprosy is needed to catch the disease. The disease is not spread through casual contact with a person who has leprosy like shaking hands or hugging, sharing meals or sitting next to each other. Moreover, the patient stops transmitting the disease when they begin treatment.
Diagnosis
The diagnosis of leprosy is done clinically. Laboratory-based services may be required in cases that are difficult to diagnose.
The disease manifests commonly through skin lesion and peripheral nerve involvement. Leprosy is diagnosed by finding at least one of the following cardinal signs: (1) definite loss of sensation in a pale (hypopigmented) or reddish skin patch; (2) thickened or enlarged peripheral nerve, with loss of sensation and/or weakness of the muscles supplied by that nerve; (3) microscopic detection of bacilli in a slit-skin smear.
Based on the above, the cases are classified into two types for treatment purposes: Paucibacillary (PB) case and Multibacillary (MB) case
PB case: a case of leprosy with 1 to 5 skin lesions, without demonstrated presence of bacilli in a skin smear.
MB case: a case of leprosy with more than five skin lesions; or with nerve involvement (pure neuritis, or any number of skin lesions and neuritis); or with the demonstrated presence of bacilli in a slit-skin smear, irrespective of the number of skin lesions.
Treatment
Leprosy is a curable disease. The currently recommended treatment regimen consists of three drugs: dapsone, rifampicin and clofazimine. The combination is referred to as multi-drug therapy (MDT). The duration of treatment is six months for PB and 12 months for MB cases. MDT kills the pathogen and cures the patient. Early diagnosis and prompt treatment can help to prevent disabilities. WHO has been providing MDT free of cost. Free MDT was initially funded by The Nippon Foundation and since 2000 it is being donated through an agreement with Novartis.
Prevention
Case detection and treatment with MDT alone have proven insufficient to interrupt transmission. To boost the prevention of leprosy, with the consent of the index case, WHO recommends tracing household contacts along with neighbourhood and social contacts of each patient, accompanied by the administration of a single dose of rifampicin as preventive chemotherapy.
WHO response
WHO provides technical support to Member States on leprosy prevention and control. Every year, WHO collates epidemiological data on leprosy from all its Member States and publishes a consolidated report in English and French in the Weekly Epidemiological Record, for data pertaining to the previous calendar year. These data are provided by countries.
After detailed consultations with countries, experts, partners and persons affected by leprosy, WHO released the Towards zero leprosy: global leprosy (Hansen’s disease) strategy 2021–2030 aligned to the neglected tropical diseases road map 2021–2030. The Strategy calls for a vision of zero leprosy: zero infection and disease, zero disability, zero stigma and discrimination and the elimination of leprosy (defined as interruption of transmission) as its goal. The four strategic pillars of the Strategy include: implementing integrated, country-owned zero leprosy roadmaps in all endemic countries; scaling up leprosy prevention alongside integrated active case detection; managing leprosy and its complications and prevent new disability; and combatting stigma and ensuring human rights are respected. The Strategy also recognizes that global and national investment in research is essential to achieving zero leprosy and includes a set of key research priorities.
WHO has developed e-learning modules that aim to enhance knowledge and skills of health workers at all levels on topics related to diagnosis, treatment of leprosy and management of disabilities. These can be accessed the OpenWHO platform.