Mycobacterium leprae is a bacteria that causes the disease leprosy (Hansen's disease).  Leprosy is a chronic disease that affects skin, peripheral nerves, and the upper respiratory tract.  Fortunately, leprosy in the United States is rare, causing less than 200 new cases per year in the U.S.  Most of these cases are from foreign immigrants.  The skin lesions of leprosy can cause large disfiguring nodules and ulcerations that develop over years.  Damage to the nerves in the skin often makes the lesions painless.  The loss of skin sensation may make injury unnoticible and these injuries are prone to infection with other bacteria.

 

Diseases

• Leprosy - disfiguring skin nodules and ulcers, peripheral nerve damage (loss of sensation in the skin)

Habitat & Transmission

• Mycobacterium leprae is found in the nasal mucosa and in the skin lesions of an infected person
• It is spread from person-to-person, probably through respiratory tract secretions

Weapons and Defenses

• Mycobacterium leprae lives within human cells where it can hide from the immune system
• Invades Schwann cells, the cells that cover the nerves, causing decreased nerve function and loss of sensation in the skin

Weaknesses

• Mycobacterium leprae is susceptible to antibiotics such as dapsone and rifampin (known to be useful for treating Mycobacterium leprae's cousin Mycobacterium tuberculosis, the cause of tuberculosis)
• Both dapsone and rifampin should be given for at least 1 year
• The BCG vaccine (a tuberculosis vaccine not available in the United States) is about 50% effective for preventing disease