Leishmaniasis laboratory tests

Overview
Diagnosis of visceral leishmaniasis may require taking a blood sample and/or taking a biopsy from the bone marrow to show the parasite. Diagnosis of cutaneous leishmaniasis will require a small biopsy or scraping of the ulcer. Diagnosis of mucocutaneous leishmaniasis requires a biopsy of the affected tissues.

Biopsy samples are examined by microscopy, culture and other methods to look for the parasite and identify the specific kind of Leishmania causing the ulcer. Some of these methods will give results within a few days, but culture may take 2-4 weeks to demonstrate the parasite.

Examination of Giemsa stained slides of the relevant tissue is still the technique most commonly used to detect the parasite.

Laboratory Findings: Microscopy
Isolation of the organism in culture (using for example the diphasic NNN medium) or in experimental animals (hamsters) constitutes another method of parasitilogic confirmation of the diagnosis, and in addition can provide material for further investigations (e.g., isoenzyme analysis). Antibody detection can prove useful in visceral leishmaniasis but is of limited value in cutaneous disease, where most patients do not develop a significant antibody response. In addition, cross reactivity can occur with Trypanosoma cruzi, a fact to consider when investigating Leishmania antibody response in patients who have been in Central or South America. Other diagnostic techniques exist that allow parasite detection and/or species identification using biochemical (isoenzymes), immunologic (immunoassays), and molecular (PCR) approaches. Such techniques, however, are not readily available in general diagnostic laboratories.



A, B: Leishmania tropica amastigotes from an impression smear of a biopsy specimen from a skin lesion. In A, an intact macrophage is practically filled with amastigotes (arrows), several of which have a clearly visible nucleus and kinetoplast; in B, amastigotes are being freed from a rupturing macrophage. Patient had traveled to Egypt, Africa, and the Middle East. Based on culture in NNN medium, followed by isoenzyme analysis, the species was L. tropica.



C: Three Leishmania amastigotes, each with a clearly visible nucleus and kinetoplast, from the same impression smear as in A and B.



D: Leishmania mexicana in a biopsy specimen from a skin lesion stained with hematoxylin and eosin. The amastigotes are lining the walls of two vacuoles, a typical arrangement. The species identification was derived from culture followed by isoenzyme analysis. Infection was acquired in Texas.

Resources
CDC Leishmaniasis Diagnosis