Laboratory diagnosis of Leishmania.

Leishmaniasis should be considered in the differential diagnosis of individuals living in or with a history of having traveled to known endemic areas and who present with signs and symptoms of visceral infection or with cutaneous or mucosal lesions. Because leishmaniae are capable of producing a wide spectrum of disease in humans, the clinical manifestations overlap with many other diseases. Definitive diagnosis of Leishmania infection in the laboratory requires demonstration of the parasite in smears, in biopsies, or by isolation of the organism in culture media or in experimental animals. Many other methods for demonstration of parasites (histochemical and immunohistochemical) or for detecting the presence of antibodies against leishmaniae (serologic) have been described. Many advances have been made in these areas, but the methodology and the technology involved in immunohistochemistry and serology remain outside the reach of the standard clinical diagnostic laboratory, which both in developed and less developed countries still relies on demonstration of the parasites in smears stained with Giemsa stain and on biopsy specimens processed and stained with hematoxylin and eosin stain. The newer serologic techniques, such as ELISA with several variations, IFAT, and others, are largely research tools with the greatest use in seroepidemiologic surveys.