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Hansen’s Disease (Leprosy): Etiology: Mycobacterium leprae and its transmission (For Professionals)

  • Mycobacterium leprae is the cause of leprosy – the organism being first discovered by Armauer Hansen in 1873. The infected human being is considered to be the only source of infection.
  • Although 4% of the nine-banded armadillo in the USA have naturally acquired leprosy-like disease, only a handful of the spread from the armadillo to human has been confirmed.
  • Leprosy bacilli are rarely found in intact skin.



  • Transmission is incompletely understood. Susceptibility to leprosy shows considerable variation from absolute refractoriness to complete absence of resistance. Only less than 10% of any population is susceptible of catching the leprosy bacillus. Among the susceptible persons, only a few are prone to develop the disease.
  • The nasal mucosa and ulcerated skin lesions of bacilliferous patients are the main exit of bacilli. Inhalation of bacilli-laden droplets and contact of bacilli-laden droplets on damaged skin is considered to be the most important means of entry. An intra-familial contact is more risky than an occasional extra-familial one. Congenital transmission of leprosy does not occur.



Source of information: here