zoonoses and communicable diseases common to ... - PAHO/WHO

LEPROSY 149LEPROSYICD-10 A30.9 leprosy, unspecifiedSynonyms: Hansen’s disease, hanseniasis.Etiology: Mycobacterium leprae,a polymorphic acid-alcohol-fast bacillus that upto now has been impossible to culture in artificial laboratory media or in tissue cultures.M. leprae is difficult to distinguish from other unculturable mycobacteria naturallyaffecting animals.The failure of attempts to culture M. leprae in vitro constitutes a great barrier tobetter determining its biochemical characteristics for identification purposes as wellas for therapeutic and immunologic studies. In part, this difficulty has been overcome,first by in vivo culture on mouse footpads and later in nine-banded armadillos(Dasypus novemcinctus). At present, the latter serve as a model for lepromatousleprosy and provide a large number of bacilli for research.In identification of M. leprae, the dopa (3,4-dihydroxyphenylalanine) oxidationtest and extraction with pyridine are of value. Homogenate of human leproma (granulomatousnodule rich in M. leprae and characteristic of lepromatous leprosy) oxidizesdopa to indole. Extraction with pyridine eliminates the acid-fast quality of M.leprae, but not that of other mycobacteria.In recent years, more precise identification of M. leprae has been achieved bystructural analysis of its mycolic acids, analysis by immunodiffusion of its antigens,and interaction of leprosy bacilli with bacteriophages specific for mycobacteria(Rastogi et al., 1982).Occurrence in Man: Leprosy is endemic in 93 countries. Eighty percent of allrecorded cases are concentrated in five countries: India, Brazil, Nigeria, Myanmar(Burma), and Indonesia (WHO, 1988). The highest prevalence is found in the tropicaland subtropical regions of Asia, Africa, Latin America, and Oceania. Leprosy isvery prevalent in India, Southeast Asia, the Philippines, Korea, southern China,Papua New Guinea, and some Pacific islands. Ninety percent of the cases reported inLatin America come from five countries: Argentina, Brazil, Colombia, Mexico, andVenezuela (Brubaker, 1983). Chile is the only South American country free of theinfection. In the United States, most cases occur among immigrants. Autochthonouscases arise in Hawaii, Puerto Rico, Texas, and Louisiana. The infection’s prevalenceis related to the population’s socioeconomic level. The fact that the disease has practicallydisappeared in Europe is attributed to the improved standard of living there.There are differences in the regional or racial prevalence of tuberculoid and lepromatousleprosy. Ninety percent of the cases in endemic areas of Africa and 80%of the cases in India are of the tuberculoid type. The lepromatous form represents30% to 50% of cases among the white population or in some Asian countries suchas Japan, China, and Korea (Bechelli et al., 1972).In countries with efficient control programs, it was expected that prevalencewould fall by 60% to 80% by the year 2000. Of the cases reported worldwide, 49.1%were under multidrug treatment in 1990 (Noorden, 1990). The cumulative rate ofcoverage with polychemotherapy has reached 82%. Each year 1.4 million patientsare freed from the disease (WHO, 1993).