Leprosy

Epidemiology of Infectious Diseases: Leprosy

Causal agent
A chronic bacterial disease of the skin, peripheral nerves and (in lepromatous patients) the upper airway caused by Mycobacterium leprae1,3.

Common clinical features
Leprosy is a chronic infectious disease affecting the skin and peripheral nerves, but has a wide range of clinical manifestations. Patients are classified as having either paucibacillary or multibacillary leprosy.

Paucibacillary leprosy  is a milder disease and is characterized by up to 5 hypopigmented skin macules1.

Multibacillary leprosy is associated with multiple (> 5) skin lesions, nodules, plaques, thickened dermis, and frequent involvement of the nasal mucosa1.

Untreated it can cause permanent damage to the skin, nerves, limbs and eyes.

Epidemiology

  • In 1981 the WHO recommended the use of multi-drug therapy as a standard treatment for leprosy and in 1991 the World Health Assembly passed a resolution declaring its commitment to eliminate leprosy as a public health problem by the end of 2000.
  • As a result there has been a dramatic decrease in the global burden of leprosy over the last 20 years. Worldwide cases decreased from approximately 5.2 million in 1985 to 410,000 cases at the end of 2004. This decrease has been the result of widespread use of multi-drug therapy.
  • Between 1985 and 2005 over 14 million leprosy cases were diagnosed and treated with multi-drug therapy.
  • In nine countries in Asia, Africa and Latin America (Angola, Brazil, Central African Republic, Democratic Republic of Congo, India, Madagascar, Mozambique, Nepal and the United Republic of Tanzania) leprosy is still considered a public health problem and accounts for a > 80% of the global disease burden.

Reservoir
Humans 

Mode of transmission
Thought to be person to person via respiratory droplets.

Incubation period
9 months to 20 years. The average is thought to be 4 years from tuberculoid leprosy and 8 years for lepromatous leprosy2.

Period of Communicability
Infectiousness is lost in most cases following the first dose of multi-drug therapy1.

Diagnosis and Treatment
Multi-drug therapy is highly effective. The World Health Organisation recommends multi drug treatment comprising dapsone, rifampicin and clofazimine. 

Prevention and control

  • Early detection.
  • Adequate treatment of cases with multiple drug therapy (MDT) which consists of dapsone, rifampicin and clofazimine.
  • Prevention of disabilities and rehabilitation for leprosy patients.

References

  1. Centers for Disease Control and Prevention. Hansen's Disease Fact Sheet, October 2005.
     
  2. Heymann D L, editor, Control of Communicable Disease Manual. 18th ed. American Public Health Association; 2004.
     
  3. Hawker J, Begg N, Blair I, Reintjes R, Weinberg J. Communicable Disease Control Handbook, Blackwell, 2005.

Further Resources

World Health Organisation, Global Strategy for Further Reducing the Leprosy Burden as a Public Health Problem and Sustaining Leprosy Control Activities (plan period 2006 - 2010). World Health Organisation, 2005.  Available online at:
http://www.who.int/lep/Reports/GlobalStrategy-PDF-verison.pdf

© CM Kirwan 2006