Leprosy (Hansen’s disease) factsheet for Healthcare professionals

(Please read in conjunction with the companion factsheet on Leprosy (Hansen’s disease) for the general 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).

The type of leprosy which develops reflects the degree to which the person is able to mount a cell-mediated immune response. The three main types are lepromatous, tuberculoid, and borderline. Tuberculoid leprosy is not related to tuberculosis (TB). Types of disease may be classified according to the Ridley-Jopling classification, which is based on skin lesion type and bacterial load:

• Tuberculoid leprosy (TT): patients have a vigorous cell-mediated immune response. This results in well-demarcated lesions containing few bacilli and surrounded by lymphocytes.
• Lepromatous leprosy (LL): patients do not develop an effective cell-mediated immune response. Lesions are diffusely infiltrated with macrophages in which bacteria multiply in large numbers. Antibodies are produced, often in large quantities, but are ineffective in killing the bacilli.
• Borderline leprosy: this category covers the spectrum between the two extremes described above. Patients have some cell-mediated immune response, multiple lesions and unstable immunity. Borderline leprosy can be further classified according to the category it most resembles:
  • Borderline tuberculoid (BT)
  • Borderline (mid-borderline) (BB)
  • Borderline lepromatous (BL)

Table 1 shows the different classifications and features of leprosy, and their correlation with the “Bacteriological Index”, which is a measure of the number of leprosy bacilli seen in stained material obtained from slit skin smears.

Table 1: WHO classification and features of leprosy.

How common is leprosy?
Leprosy mainly occurs in the tropical and sub-tropical countries, and is still present in some parts of southern Europe, the Middle East, and North Africa. The introduction of multi-drug treatment for leprosy in the 1980s in conjunction with childhood vaccination with BCG to prevent tuberculosis has resulted in a considerable reduction in the global prevalence of leprosy.

Leprosy is not commonly seen in Ireland. Less than 5 cases have been reported to the Health Protection Surveillance Centre (HPSC) within the last 5 years; all of whom acquired their leprosy outside of Ireland.

What is the incubation period?
The M. leprae bacteria that causes leprosy reproduces rather slowly, and the incubation period (i.e. time from being infected to development of symptoms) of the disease varies from a few months to 30 years. On average, it takes approximately 5 years for symptoms to present.

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.

What are the clinical features?

• Skin lesion(s):
  • Chronic non-itchy patch with or without hypopigmentation (macular, annular or occasionally plaque),
  • Altered sensation (to light touch, temperature and/or pain),
  • Widespread maculation and/or infiltration with or without papules or nodules;
• Peripheral nerve trunk damage and/or pain;
• Thickened peripheral nerves;
• Ulceration on sole of foot;
• If presenting in reaction:
  • Acute erythema and oedema of skin lesions,
  • Sudden change in previously flat skin lesions,
  • Neuritis,
  • Other sudden change in symptoms;
• Less commonly:
• • Erythema nodosum with or without fever,
  • Hoarseness,
  • Arthritis,
  • Orchitis,
  • Acute uveitis (very rare).

What is the aetiological agent?
The agent is Mycobacterium leprae (M. leprae) (a bacillus), which multiplies very slowly (approximately every 13 days) and mainly affects the skin, nerves, and mucous membranes.

The organism has never been grown in bacteriological media or cell culture, but has been grown in mouse foot pads and nine-banded armadillos.

Laboratory criteria
At least one of the following two:

• Demonstration of characteristic acid-fast bacilli in skin or dermal nerve, obtained from either a punch biopsy or a slit skin biopsy of a lepromatous lesion (depending on the clinical presentation). The identity of Mycobacterium leprae can be confirmed by nucleic acid amplification tests.
• Histopathological report from skin or nerve biopsy compatible with leprosy (Hansen’s disease) examined by a consultant pathologist experienced in leprosy diagnosis.

Some serological tests have been developed and promoted by some investigators, but they lack sufficient sensitivity and specificity to be used as diagnostic tests and for this reason are not widely used.

In suspected cases, advice from a medical doctor (usually an Infectious Diseases/Microbiology Consultant) should be sought.

How is leprosy treated?
It is important to know that leprosy can be cured. Early treatment will prevent disability. Medication should be administered under the supervision of a medical doctor (usually an Infectious Diseases/.Microbiology Consultant). 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.

What is the role of the clinician?
The role of the clinician is to:

• Maintain an index of suspicion;
• Discuss any suspected cases with a medical doctor (usually an Infectious Diseases/Microbiology Consultant), before slit skin smears and/or biopsies are taken;
• Ensure that any microbiology or pathology specimen taken are gathered correctly and sent to reference laboratories with appropriate expertise; and
• 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, or
• 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), and
• Ensure that adequate surveillance information is gathered for HPSC, in order to comply with international reporting obligations and for the purposes of national surveillance.

Is there a vaccine available for leprosy?
Currently there is no vaccine available in worldwide against leprosy. However, in 2016, the WHO launched a new global strategy – “The Global Leprosy Strategy 2016 – 2020: Accelerating towards a leprosy-free world” – which aims to reinvigorate efforts for leprosy control and to avoid disabilities, especially among children affected by the disease in endemic countries.

Further information is available from:
World Health Organization (WHO), 2016. Available URL: http://www.who.int/mediacentre/factsheets/fs101/en/ (Accessed: 14th July 2016)
World Health Organization (WHO), 2016. Available URL: http://www.searo.who.int/entity/global_leprosy_programme/documents/global_leprosy_strategy_2020/en/ (Accessed: 15th July 2016)
Public Health England (PHE), 2013. Available URL: https://www.gov.uk/guidance/leprosy (Accessed: 14th July 2016)
National Institute for Health and Care Excellence (NICE), 2016. Available URL: http://www.evidence.nhs.uk/Search?ps=20&q=Leprosy (Accessed: 14th July 2016)
Centre for Disease Control and Prevention (CDC), 2013. Available URL: https://www.cdc.gov/leprosy/ (Accessed: 14th July 2016)
New South Wales (NSW) Australia, 2012. Available URL: http://www.health.nsw.gov.au/Infectious/factsheets/Factsheets/leprosy.PDF (Accessed: 14th July 2016)
Irish Statue Book (ISB), 2011. Available URL: http://www.irishstatutebook.ie/eli/2011/si/452/made/en/print (Accessed: 26th July 2016)

Last updated: 7 November 2016