Leprosy: 5 Critical Facts on Hansen’s Disease & MDT

Leprosy (Hansen’s Disease) is a chronic, curable infectious disease caused mainly by Mycobacterium leprae, affecting skin, peripheral nerves, mucosa of the upper respiratory tract, and eyes; early diagnosis and multidrug therapy (MDT) prevent disability and stop transmission.

📌 Key Takeaways: Leprosy (Hansen’s Disease)

• Causative Agent: Chronic granulomatous infection caused primarily by Mycobacterium leprae, affecting the skin, peripheral nerves, and mucosal surfaces.
• Transmission: Transmitted via respiratory droplets during prolonged, close contact with untreated multibacillary cases; non-infectious shortly after starting treatment.
• Cardinal Diagnostic Signs: Loss of sensation in skin patches, enlarged/thickened peripheral nerves, or positive acid-fast bacilli on slit-skin smear.
• WHO Treatment: Curable with Multidrug Therapy (MDT)—PB cases receive Rifampicin + Dapsone (6 months); MB cases receive Rifampicin + Dapsone + Clofazimine (12 months).

Definition:

• Leprosy is a chronic granulomatous infection caused by Mycobacterium leprae (and rarely M. lepromatosis), primarily involving skin and peripheral nerves, with potential involvement of eyes, nasal mucosa, and other organs.
• It is classified as a neglected tropical disease (NTD) and remains endemic in over 120 countries, with India, Brazil, and Indonesia accounting for the majority of new cases.

Causative Agents and Transmission:

1. Causative agent

• Mycobacterium leprae: slow-growing, acid-fast, obligate intracellular bacillus; cannot be cultured in artificial media.

2. Mode of Transmission:

• Primarily via respiratory droplets from untreated multibacillary (MB) cases during prolonged, close contact.
• Not spread through casual contact (handshakes, sharing food, sitting together).
• Patient becomes non-infectious soon after starting MDT.

Reservoirs:

• Humans are the main reservoir: armadillos and some environmental sources implicated in specific regions.

Classification and Types:

Leprosy presents along an immunological spectrum (Ridley-Jopling classification):

Type	Immune response	Bacillary load	Lessons	Nerve involvement	Infectivity
Indeterminate	Early, unstable	Very low	1-few hypopigmented macules	Minimal	Low
Tuberculoid (TT)	Strong cell-mediated	Paucibacillary (PB)	A few, well-demarcated hypopigmented/erythematous plaques with loss of sensation	Asymmetric,thickned nerves	Low
Borderline Tuberculoid (BT)	Moderate	PB	More lesions than TT, satellite lesions	Moderate	Moderate
Borderline Borderline (BB)	Unstable	Intermediate	Annular plaques, “inverted saucer” appearance	Multiple nerves	Moderate-high
Borderline Lepromatous (BL)	Weak	Multibacillary (MB)	Numerous, poorly defined lesions and nodules.	Symmetric,widespread	High
Lepromatous (LL)	Very weak/absent	MB	Diffuse infiltration, nodules (leonine facies), symmetric nerve damage.	Severe,symmetric	High

For treatment purposes, the WHO simplifies it to the following:

1. Paucibacillary (PB): 1 to 5 skin lesions, no bacilli on smear.
2. Multibacillary (MB): more than 5 lesions, nerve involvement, or smear positive.

Clinical features and symptoms:

1. Early signs:

• Hypopigmented or reddish skin patches with loss of sensation (touch, pain, and temperature).
• Thickened peripheral nerves, e.g., ulnar, median, lateral popliteal, and posterior tibial.

2. Common symptoms:

• Skin lesions that do not heal for weeks or months.
• Numbness/tingling in hands, feet, arms, and legs.
• Muscle weakness, wasting, claw hand, and foot drop.
• Nasal stuffiness, epistaxis, septal perforation.
• Eye involvement: lagophthalmos, iritis, blindness.
• Deformities: contractures, trophic ulcers, and auto-amputation of digits.

Leprosy reactions (acute episodes):

1. Type I (reversal) reaction: Type IV hypersensitivity, sudden inflammation of existing lesions, nerve pain, and risk of permanent nerve damage.
2. Type II (Erythema Nodosum Leprosum, ENL): Immune complex-mediated; fever, tender nodules, neuritis, arthritis, and orchitis.

Diagnosis:

Cardinal signs (any one sufficient for diagnosis):

1. Definite loss of sensation in a hypopigmented/reddish skin patch.
2. Thickened/enlarged peripheral nerve with sensory/motor loss.
3. Slit-skin smear positive for acid-fast bacilli.

Clinical Diagnosis:

Primarily clinical, based on history and examination by trained health workers.

Diagnostic methods:

1. Skin examination: distribution, number, type of lesions; sensory testing with cotton/touch.
2. Nerve examination: palpation for thickening, tenderness, and motor/sensory function.
3. Slit-skin smear: bacterial index (BI) and morphological index (MI); more useful in MB cases.
4. Skin biopsy: histopathology (granulomas, bacilli); used in atypical cases.
5. Molecular tests: PCR for M. leprae DNA (research/reference labs).
6. Serology: anti-PGL-1 antibodies (supportive, not diagnostic alone).

Treatment:

Multidrug Therapy (MDT)—WHO regimen:

1. PB leprosy: Rifampicin + Dapsone for 6 months.
2. MB leprosy: Rifampicin + Dapsone + Clofazimine for 12 months.

MDT is free under the National Leprosy Eradication Programme (NLEP) in India.

Management of reactions and complications:

1. Type I: Oral corticosteroids (prednisolone) to prevent nerve damage.
2. Type II (ENL): Corticosteroids; thalidomide (where approved, with strict controls).
3. Nerve function impairment: Physiotherapy, protective care, splints, and reconstructive surgery if needed.
4. Ulcer care: wound management, footwear, and infection control.
5. Follow-up: Monthly drug refills, adherence counseling, monitoring for reactions, and disability.

Prevention and Control Measures:

1. Primary prevention:

• Early case detection and prompt MDT to interrupt transmission.
• Post -exposure prophylaxis (PEP): Single-dose rifampicin (SDR) for eligible contacts after ruling out active leprosy and TB.
• BCG vaccination: provides partial protection; included in many national schedules.

2. Secondary prevention:

• Regular contact screening (household, neighborhood, and social contacts)
• Surveillance of high-risk groups (slums, tribal areas, migrants).
• Disability prevention and rehabilitation services.

3. Tertiary prevention:

• Reconstructive surgery, physiotherapy, and occupational therapy.
• Socioeconomic rehabilitation, microcredit, and livelihood support.

Environmental & health system measures:

• Integration into general health services.
• Training of ASHAs, ANMs, and medical officers.
• Strengthening referral systems and drug supply chains.

Magnitude and Epidemiology:

1. Global:

• ~ 200,000 new cases reported annually worldwide; > 120 countries still report cases.
• The Southeast Asia region accounts for the majority of global new case detections.
• Elimination at a global level (prevalence < 1/10,000) was achieved in 2000; the focus now is on zero transmission, zero disability, and zero discrimination.

2. India:

• India contributes the highest number of new cases globally, along with Brazil and Indonesia.
• The prevalence rate declined from 57.2/10,000 (1981) to 0.57/10,000 (2025).
• Proportion of child cases (indicator of recent transmission) fell from 9.04% (2014-15) to 4.68% (2024-25).
• Endemic pockets persist in states like Uttar Pradesh, Bihar, Jharkhand, Chhattisgarh, Odisha, Maharashtra, and some northeastern states.

3. Global risk:

• Continued transmission in high-burden countries poses the risk of importation to low-endemic areas.
• Drug-resistant strains and delayed diagnosis increase the risk of disability and onward transmission.

Public Awareness, Community Engagement & IEC Materials:

Objectives:

• Promote early recognition of symptoms and help-seeking.
• Reduce stigma and discrimination.
• Encourage contact screening and treatment adherence.

IEC/BCC strategies (as per WHO & NLEP):

• Posters, leaflets, and flip charts showing early signs (insensitive patches, nerve thickening)
• School programs: Leaflets, pictograms for school medical inspection.
• Street plays (Nukkad Natak), cultural programs, and testimonials from cured persons.
• Self-examination for minors, interactive quizzes, and pledge campaigns against discrimination.
• Radio/TV spots, social media campaigns around National Leprosy Day (30 January)

Evidence shows focused IEC with community volunteers sustains knowledge and improves early detection.

Role of Public Health Department:

At the national/state level, e.g., NLEP, India:

• Policy formulation, planning, and resource allocation.
• Procurement and distribution of MDT drugs and diagnostic kits.
• Training of health personnel and supervision of districts.
• Monitoring and evaluation: case detection rates, treatment completion, and disability grades.
• Coordination with NGOs and international partners (WHO, global partnership for zero leprosy).

At the district/PHC levels:

• Active case finding through surveys, camps, and outreach.
• Ensuring contact tracing and SDR-PEP implementation.
• Maintaining leprosy registers and reporting to state / national dashboards.
• Organizing IEC activities, school health programs, and community meetings.
• Referral for reactions, disability management, and reconstructive surgery.
• Integration with general health services, TB programs, and NCD clinics.

Key Challenges and Priorities:

• Hidden cases due to stigma and low awareness in marginalized communities.
• Diagnostic delays leading to grade 2 disabilities at presentation.
• Need for simplified field-friendly diagnostics, e.g., rapid tests.
• Strengthening contact management and PEP coverage.
• Sustaining political commitment and funding as prevalence declines.