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 Bacterial Diseases - LEPROSY

(Hansen's disease)

AGENT:

Mycobacterium leprae, a polymorphic acid-fast bacillus.

RESERVOIR & INCIDENCE:

The world prevalence is estimated to be between 10 and 12 million. Newly recognized cases in the USA are diagnosed principally in California, Hawaii, Texas, Florida, Louisiana, and New York City, and in Puerto Rico. Most of these cases are in immigrants and refugees whose disease was acquired in their native country; however, the disease remains endemic in Hawaii, Texas, California, Louisiana and Puerto Rico. Man is the only significant reservoir. Armadillos, mangabey monkeys, and chimpanzees can acquire the disease from humans. Epidemiologic data on leprosy in the U.S. reveal very high ratios of native to foreign-born leprosy patients in Texas and Louisiana in comparison to all other states. These are the 2 states known to have the highest prevalence's of leprosy in wild armadillos.

TRANSMISSION:

Respiratory and involves prolonged exposure in childhood. Only rarely have adults become infected.

DISEASE IN ANIMALS:

The disease in armadillos (Dasypus novemcinctus) is similar to the lepromatous form in man. Infection in these animals is characterized by macrophage infiltrates containing a large number of bacilli. M. leprae is known to prefer the coldest parts of the human body. For this reason, armadillos are used as experimental animals since their body temperature is 30-35º C. In chimpanzees, the disease appears as a progressive chronic dermatitis with nodular thickening of the skin of the ears, eyebrows, nose, and lips. Sooty mangabey monkeys develop lepromatous leprosy with neuropathic deformities of the extremities, including clawing of the digits.

DISEASE IN HUMANS:

In lepromatous leprosy, nodules, papules, macules and diffuse infiltrations are bilaterally symmetrical and usually numerous and extensive; involvement of the nasal mucosa may lead to crusting, obstructed breathing and epistaxis; ocular involvement leads to iritis and keratitis. In tuberculoid leprosy, skin lesions are single or few, sharply demarcated, anesthetic or hyperesthetic, and bilaterally asymmetrical; peripheral nerve involvement tends to be severe.

DIAGNOSIS:

Demonstration of acid-fast bacilli from skin or nasal septum scrapings.

TREATMENT:

Combination therapy is recommended since single-drug treatment is accompanied by emergence of resistance. Lepromatous leprosy is treated with dapsone, clofazimine, and rifampin. Tuberculoid leprosy is treated with dapsone and rifampin.

PREVENTION/CONTROL:

Early detection and treatment. Contact isolation for lepromatous leprosy but not necessary for tuberculoid leprosy.