Introduction

Leishmaniasis is infection by protozoan parasites of the genus Leishmania. The most common clinical presentation is localized ulcer or nodule. The organisms are transmitted to humans by the bite of female sandflies (Phlebotomus in the Eastern Hemisphere; Lutzomyia in the Western Hemisphere). In endemic areas, nonhuman mammalian species serve as reservoir hosts.

CL is endemic in over 80 countries. In the Americas, it is widely distributed from southern Texas to northern Argentina. Other endemic areas include the Middle East, India, and East Africa. Worldwide, approximately 300,000 cases of CL are reported annually from an at-risk population of 200 million. Epidemics of CL frequently occur when a nonimmune population intrudes into a natural enzootic cycle. The population at highest risk for CL is nonimmune expatriates such as tourists, soldiers, new settlers, and construction or agricultural workers. Socioeconomic factors, population growth, and migration also influence the epideminology of CL.

Clinical syndromes of CL vary according to the infecting species and geographic distribution, but no species is uniquely associated with a particular clinical syndrome. In the East, L. tropica is the major cause of various forms of CL, especially in urban areas. Recent cases from Iraq have been caused by L. major. Diffuse CL is associated with L. aethiopica in the East and with L. mexicana complex in the West. Leishmania brasiliensis complex, L. guyanensis, and L. panamensis cause mucocutaneous leishmaniasis in the West. Leishmania amazonenesis causes various CL syndromes in Brazil. Leishmania donovani and L. infantum in the East and L. chagasi in the West cause visceral leishmaniasis. The majority of cases seen in military and civilian personnel serving in the Middle East have been identified in culture or by PCR as L. major.