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Leishmaniasis

Leishmaniasis has been called a "dynamic disease," gradually spreading, with new foci of infection arising in scattered areas of the globe. The WHO has estimated that there are 12 million people infected and 350 million at risk (1992). There are over 5,000 new cases a year in Peru alone, and it is estimated that the real incidence is three times as great. In the Mediterranean countries it has become a common opportunistic infection for HIV?positive patients.

Synonyms

The synonym "kala azar" comes from Hindi, and means black poison or black fever, because of the darkening of skin pigmentation on the forehead and hands; other local names are given to the different patterns of the disease.

Definition

Leishmaniasis is a widespread disease due to infection with one of the species of the protozoa of the genus Leishmania, family Trypanosomatidae. There are many, at least 14, different subspecies, each with a significant geographic distribution and each causing a different pattern of illness. The majority are transmitted to man by female sand-flies (Psychodidae) of the genus Phlebotomus, or, in the Americas, Lutzomyia or Psychodopogus. Leishmaniasis is essentially a zoonosis, although in certain areas man is the sole host. In other regions man is a casual host and the infection is chiefly in dogs, rodents, and other mammals. An infection by one species may provide immunity to other Leishmania, but there are specific and group antigens, and cross-immunity does not occur between all species. Vaccines can be prepared from some species (e.g., L. mexicana) and there are useful skin tests.

Clinical Characteristics

The clinical presentation is very variable, but there are three types of leishmaniasis: (a) visceral,
(b) cutaneous, and (c) mucocutaneous. Only the visceral form has any significant radiological findings.

Visceral Leishmaniasis (Kala Azar)

Visceral leishmaniasis is a predominantly rural disease and is caused by Leishmania donovani, L. tropica, or L. chagasi. About half the world's annual cases of visceral leishmaniasis occur in Bihar State, in northeastern India; many cases also occur around the Mediterranean, in Iraq, Iran, Arabia, southern Russia, and parts of China, in subSaharan Africa (Senegal, Nigeria, Sudan, Chad, Somalia, Kenya, Uganda), and in South and Central America (Brazil, Paraguay, Colombia, Venezuela, Guatemala, Mexico) (Fig. 46.11).

Fig. 46.11. Geographic distribution of leishmaniasis.

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Copyright: Palmer and Reeder