Leprosy (Hansen’s disease) factsheet for Healthcare professionals

Please read in conjunction with the companion factsheet on Leprosy (Hansen’s disease) factsheet for the public, which provides a detailed description of Leprosy.

What is Leprosy?
Leprosy is a curable chronic infectious disease caused by a bacterium called Mycobacterium leprae (M. leprae). It is rarely seen in Ireland.

1. leprae is a slow-growing, acid-fast, and Gram-positive bacillus. It multiplies very slowly (approximately every 13 days) and mainly affects the skin, nerves, and mucous membranes of the eyes and nose. It is stained with a modified Ziehl-Neesen stain and appears as fine red rods against a blue background.
2. Tuberculoid (TT)
3. Borderline Tuberculoid (BT)
4. Borderline (BB)
5. Borderline Lepromatous (BL)
6. Lepromatous (LL)

Following an initiative from the World Health Organization (WHO) to eliminate Leprosy, drug treatment was made available free of charge to all patients worldwide since 1995. The elimination of Leprosy as a public health problem was achieved in 2000 due to a combination of multi-drug treatment and childhood vaccination with BCG for tuberculosis. Now, the disease is rarely seen; but when seen, it can be easily and effectively treated. It currently has a worldwide prevalence rate of 16.9 per 1 million persons, of which most cases are found in Africa and Asia.

Classification

The type of Leprosy that develops is determined by the degree to which a person is able to mount a cell-mediated immune response. This is determined by a Lepromin skin test.

Leprosy is classified based on clinical manifestations and skin smear results. There are different classification systems.

One classification system is the Ridley-Jopling Classification 1966. This divides the spectrum of Leprosy into 5 groups:

Type of Leprosy	Features
Tuberculoid	Vigorous cell-mediated immune response means that lesions are well-demarcated with few bacilli and are surrounded by lymphocyte granulomas.
Lepromatous	Cell-mediated immune response is not sufficient and many lesions form. Foam cells (lipid-laden macrophages) are seen which contain many bacilli. Antibodies are produced but are ineffective at killing the bacilli.
Borderline	Covers the spectrum between the two extremes of TT and LL. Patients have some cell-mediated immune response, multiple lesions, and unstable immunity. It can be further classified into BT, BB, and BL.

Table 1: Ridley-Jopling Classification of Leprosy

Another classification system is the WHO Classification of Leprosy 1981. This divides Leprosy into 2 groups:

1. Paucibacillary
2. Multibacillary

Feature	Paucibacillary	Multibacillary
Number of skin lesions	1 – 5	>5
Distribution	Asymmetrical	Symmetrical
Loss of sensation	Definite loss	May or may not be present
Bacilli present in slit-skin smear	No	Yes
Ridley-Jopling classification	TT BT	BB BL LL

Table 2: WHO classification and features of Leprosy

The Bacteriological Index (BI) and Morphological Index (MI) of Leprosy can be calculated based on the number of M. leprae and their morphology. BI is an expression of the extent of bacterial loads. MI is calculated by counting the number of solid-staining acid-fast rods. Both are used to assess the amount of infection, the viability of the organisms, and the progress of the patient under treatment.

Grading	Bacteriological Index (BI)	Type of Leprosy
0	Absence of AFB in 100 fields	TT
1+	1-10 AFB per 100 fields	BT
2+	1-10 AFB per 10 fields	BB
3+	1-10 AFB per field	BL
4+	10-100 AFB per field	BL
5+	100-1000 AFB per field	LL
6+	>1000 AFB per field	LL

Table 3: Bacteriological Index based on slit-skin smears

 

Clinical features of Leprosy

Because M. leprae grows very slowly, the person who is infected may not have any symptoms for a few months to a few decades. On average, it takes about 5 years for symptoms to occur.

• Paucibacillary (or tuberculoid) Leprosy:
• Asymmetrically distributed hypopigmented or hyperpigmented skin macules with anaesthesia
• Peripheral nerve swelling and enlargement (may or may not be tender to palpate)
• Complications of loss of sensation, including chronic ulceration of the soles of the feet and corneal ulcers. 

• Multibacillary (or lepromatous) Leprosy:
• Symmetrically distributed, diffuse, ulcerated skin nodules or plaques containing large numbers of acid-fast bacilli packed in foam cells
• Thickened peripheral nerves and dermis
• Nasal mucosa involvement – congestion and epistaxis
• Systemic disease affecting the eyes, nose, testes, and bones
• Complications – erythema nodosum, saddle-nose deformity, staphyloma (protrusion of the pigmented wall of the eyeball)

• Borderline Leprosy:
• Skin lesions tend to be of the tuberculoid type but are more numerous and diffuse
• Peripheral nerves affected

• If presenting with an acute reaction:
• Acute erythema and oedema of lesions
• Development of new lesions
• Fever
• Neuritis
• Orchitis
• Lymphadenitis
• Nephritis
• Arthralgias
• Lucio’s phenomenon (multiple hard-to-heal ulcers seen in those with lepromatous Leprosy who are of Mexican ancestry)

Who is susceptible to Leprosy?
Most adults around the world are not susceptible to catching Leprosy. Reports in the literature suggest that 95% of adults are naturally unable to contract the disease, even when they are exposed to the M. leprae bacteria. Persons at greatest risk are those who live in the same household as a person with untreated Leprosy for more than a month. This is because extended contact is required to become infected with Leprosy.

Patients with Leprosy can normally live at home, continue normal family life, work, attend hospital out-patients or be admitted to a general hospital without danger to others.

Diagnosis

Diagnosis is mainly based on clinical findings, although laboratory-based diagnosis can be used for more difficult cases. Because the disease commonly manifests as skin lesions and peripheral nerve involvement, diagnosis is based on the presence of at least 1 of the following cardinal signs:

1. Definite loss of sensation in a pale or reddish skin patch
2. Thickened or enlarged peripheral nerve with a loss of sensation and/or weakness of the muscles supplied by that nerve
3. Microscopic detection of bacilli in a slit-skin smear

Serologic test for IgM against phenolic glycolipid-1 is useful in the diagnosis of only lepromatous Leprosy.

Treatment of Leprosy
Leprosy can be cured with multidrug therapy consisting of Rifampicin, Dapsone, and Clofazimine. Duration is dependent of type of Leprosy:

• Paucibacillary - 6 months
• Multibacillary - 12 months

Medication is be administered under the supervision of a medical doctor, normally an Infectious Diseases or Microbiology Consultant. Early treatment will prevent disability.

Most patients with newly diagnosed Leprosy can be treated as out-patients without risk to themselves or others. Hospital admission may be indicated for medical or other reasons, including the management of complications including ulcers, burns or secondary infections.

Is there a vaccine available for Leprosy?
Currently there is no vaccine available for Leprosy. However, there are some vaccines currently undergoing clinical trials. 

What is the role of the clinician?

• Maintain an index of suspicion
• Discuss any suspected cases with a medical doctor (usually an Infectious Diseases/Microbiology Consultant) before slit-skin smears or biopsies are taken
• Ensure that any microbiology or pathology specimen taken are gathered correctly and sent to reference laboratories with appropriate expertise
• Notify the relevant Medical Officer of Health in the local Department of Public Health

Is Leprosy a notifiable disease?
Leprosy is a notifiable disease under the Infectious Diseases (Amendments) Regulations, 2011. Registered medical practitioners and medical laboratories are required to notify the Medical Officer of Health in regional Departments of Public Health. Individual cases should be managed by a medical doctor (usually an Infectious Diseases/Microbiology Consultant), and this includes any of the following cases:

• Newly diagnosed cases of Leprosy
• Cases with relapsed Leprosy
• Cases of Leprosy new to Ireland and on multi-drug therapy
• Cases of Leprosy new to Ireland, diagnosed abroad and not on multi drug therapy

What is the Public Health response?
Public Health action focuses on the effective treatment of infected persons and risk reduction of spread. The following features should be introduced:

• Ensure that the patient is being managed by, or in conjunction with, a medical doctor (usually an Infectious Diseases/Microbiology Consultant)
• Ensure contact tracing is carried out by a Medical Officer of Health (in the relevant regional Departments of Public Health) and discuss the management of household contacts with a medical doctor (usually an Infectious Diseases/Microbiology Consultant)
• Ensure that adequate surveillance information is gathered for HPSC, in order to comply with international reporting obligations and for the purposes of national surveillance

Further information is available from:
World Health Organization (WHO), 2016. Available URL: https://www.who.int/en/news-room/fact-sheets/detail/leprosy (Accessed: 19th October 2023).

World health Organisation (WHO), 2018. Available URL: https://iris.who.int/bitstream/handle/10665/274127/9789290226383-eng.pdf?sequence=58 (Accessed: 19th October 2023).

Centre for Disease Control and Prevention (CDC), 2013. Available URL: https://www.cdc.gov/leprosy/health-care-workers/index.html (Accessed: 19th October 2023).
New South Wales (NSW) Australia, 2012. Available URL: https://www.health.nsw.gov.au/Infectious/factsheets/Factsheets/leprosy.PDF (Accessed: 19th October 2023).

Last updated: 19^th October 2023