Leprosy, also known as Hansen’s disease, is a chronic infectious disease caused by the bacterium Mycobacterium leprae. Primarily affecting the skin and peripheral nerves, leprosy can lead to progressive and permanent disabilities if left untreated. This disease, while historically feared, is now curable with modern treatments, especially when detected and addressed in its early stages. Understanding what leprosy is, how it spreads, and how it’s treated is crucial in reducing its impact and eliminating stigma associated with this disease.
The Global Scope of Leprosy
Leprosy is categorized as a neglected tropical disease (NTD) by the World Health Organization (WHO). While global efforts have significantly reduced its prevalence, leprosy remains a public health concern in over 120 countries. Although the global elimination of leprosy as a public health problem (defined as less than 1 case per 10,000 population) was achieved by 2000, new cases continue to emerge.
In 2023, certain regions reported higher numbers of new leprosy cases. Brazil, India, and Indonesia each reported over 10,000 new cases annually. Twelve additional countries, including Bangladesh, Democratic Republic of the Congo, Ethiopia, and Nigeria, reported between 1,000 and 10,000 new cases each year. These statistics highlight that while leprosy is controllable, sustained efforts are needed, particularly in specific geographical areas.
How Leprosy is Transmitted
Leprosy is transmitted through droplets released from the nose and mouth of individuals with untreated leprosy. Transmission occurs during close and frequent contact with someone who is actively shedding the bacteria. It’s important to note that leprosy is not spread through casual contact. Activities like shaking hands, hugging, sharing meals, or simply sitting near someone with leprosy do not transmit the disease. Once a person with leprosy begins treatment, they are no longer contagious.
Diagnosing Leprosy: Key Signs and Classification
Diagnosis of leprosy is primarily clinical, relying on the identification of cardinal signs. Laboratory tests are generally not required for diagnosis but may be used in complex cases. The cardinal signs of leprosy are:
- Skin Lesions with Loss of Sensation: Definite loss of feeling in a pale (hypopigmented) or reddish patch of skin. These skin lesions are often the first noticeable sign.
- Thickened or Enlarged Peripheral Nerves: Enlarged nerves, particularly in the limbs, accompanied by loss of sensation and/or muscle weakness in the areas supplied by those nerves.
- Bacilli Detection in Skin Smears: Microscopic detection of Mycobacterium leprae bacilli in slit-skin smear samples. This lab test confirms the presence of the bacteria.
Based on these diagnostic criteria, leprosy cases are classified for treatment purposes into two types:
- Paucibacillary (PB) Leprosy: Characterized by 1–5 skin lesions and no detectable bacilli in skin smears.
- Multibacillary (MB) Leprosy: Defined by more than five skin lesions, nerve involvement, or the presence of bacilli in a skin smear, regardless of the number of skin lesions.
Effective Treatment for Leprosy: Multidrug Therapy (MDT)
Leprosy is effectively treated with multidrug therapy (MDT). MDT combines three safe and effective drugs: dapsone, rifampicin, and clofazimine. The WHO recommends a standard MDT regimen of 6 months for PB leprosy and 12 months for MB leprosy. MDT works by killing the Mycobacterium leprae bacteria, thereby curing the patient. Early diagnosis and prompt treatment with MDT are critical to prevent nerve damage and the disabilities associated with leprosy. The WHO provides MDT free of charge globally, ensuring access to treatment for all those affected.
Prevention Strategies: Contact Tracing and Prophylaxis
While early detection and MDT are crucial for individual treatment and preventing disabilities, they are not sufficient to fully stop leprosy transmission. The WHO recommends contact tracing, which involves identifying and screening household, neighborhood, and social contacts of newly diagnosed leprosy patients. As a preventative measure, a single dose of rifampicin as post-exposure prophylaxis (SDR-PEP) is administered to these contacts to reduce the risk of developing leprosy.
WHO’s Global Response to Leprosy
The World Health Organization plays a leading role in global leprosy control and prevention efforts. WHO provides technical support to countries in implementing effective leprosy programs. It also collects and disseminates global leprosy data through publications like the Weekly Epidemiological Record.
WHO launched the “Towards Zero Leprosy: Global Leprosy (Hansen’s Disease) Strategy 2021–2030,” aligned with the Neglected Tropical Diseases road map. This comprehensive strategy aims for:
- Zero leprosy transmission and disease
- Zero leprosy-related disabilities
- Zero stigma and discrimination associated with leprosy
The strategy focuses on integrated, country-specific roadmaps, scaling up prevention alongside active case finding, managing complications and preventing disabilities, and combating stigma while ensuring human rights. WHO also emphasizes the need for ongoing research and has developed e-learning modules available through the WHO Academy to enhance the skills of healthcare workers in leprosy diagnosis, treatment, and disability management.
Conclusion: Moving Towards a Leprosy-Free World
Leprosy is a curable disease, and with early diagnosis and consistent treatment, its devastating effects can be prevented. By increasing awareness, reducing stigma, and implementing WHO-recommended strategies like MDT and contact tracing, we can move closer to a world free from leprosy. Continued global collaboration and commitment are essential to eliminate leprosy and ensure that individuals affected receive the care and respect they deserve.
