Leishmania spp.: Amastigotes in Tissue
Original bench-card visuals for recognizing Leishmania donovani amastigotes (Leishman-Donovan bodies) in macrophages/Kupffer cells on Giemsa stain: small round organisms with nucleus and rod-shaped kinetoplast side by side.
Leishmania amastigote (LD body) and promastigote
Amastigote (LD body): 2-4 um, round/oval, intracellular in macrophages/Kupffer cells. Giemsa: pale blue cytoplasm, purple nucleus, rod-shaped kinetoplast at right angle to nucleus. No external flagellum. Promastigote (culture/sand...
2-4 um. Round to oval. No external flagellum. Giemsa: cytoplasm pale blue, round purple nucleus + bar-shaped kinetoplast (at roughly right angle to nucleus or perpendicular - "two dark dots" per cell). Found in macrophages, Kupffer cells (liver), spleen, bone marrow, and skin macrophages depending on species. L. donovani = visceral (kala-azar); L. major/tropica = cutaneous; L. braziliensis = mucocutaneous.
15-25 um elongated body. Anterior kinetoplast. Single anterior free flagellum. This is the form found in the sand fly vector (Lutzomyia in New World; Phlebotomus in Old World) and in NNN (Novy-MacNeal-Nicolle) culture medium. Not found in tissue smears from patients. Identifying promastigotes in culture confirms Leishmania but species-level ID requires molecular methods or isoenzyme analysis.
2-4 um. Round to oval. No external flagellum. Giemsa: cytoplasm pale blue, round purple nucleus + bar-shaped kinetoplast (at roughly right angle to nucleus or perpen...
15-25 um elongated body. Anterior kinetoplast. Single anterior free flagellum. This is the form found in the sand fly vector (Lutzomyia in New World; Phlebotomus in...
What to look for in tissue smears and biopsies
| Visual clue | Meaning | Student shorthand |
|---|---|---|
| Round 2-4 um organisms in macrophage cytoplasm | Leishmania amastigotes (LD bodies) | Giemsa on tissue impression smear or aspirate; bone marrow and spleen aspirate for visceral disease |
| Nucleus + rod-shaped kinetoplast per organism | "Two dark dots" pattern per amastigote | Both nucleus and kinetoplast stain dark purple on Giemsa; perpendicular arrangement distinguishes from Histoplasma or other round intracellular fungi |
| No external flagellum visible in tissue forms | Amastigote - expected | Flagellum present only in promastigote (insect stage); absence in tissue is a feature, not a gap |
| Elongated, anterior flagellum, anterior kinetoplast | Promastigote - culture or sand fly form | Seen in cultures; confirms Leishmania genus; molecular testing needed for species ID |
| Macrophage rupture, free amastigotes | High burden infection | Free amastigotes may be seen in smears when parasitized macrophages rupture; count associated cells for burden estimate |
Leishmania identification guide
| Pattern | What to call it | How to think about it |
|---|---|---|
| Round 2-4 um in macrophages, nucleus + kinetoplast on Giemsa | Leishmania amastigotes - positive | Report with specimen source and abundance; send PCR for species ID; clinical syndrome guides treatment selection |
| Similar cells without kinetoplast, GMS/PAS positive | Histoplasma capsulatum - not Leishmania | Kinetoplast presence is the decisive feature; run GMS if fungi are suspected alongside Leishmania |
| Promastigotes in culture or sand fly form | Leishmania spp. - genus confirmed | Culture on NNN medium at 22-26 degrees C; species ID by PCR/RFLP or isoenzyme electrophoresis |
- Amastigote (LD body): round 2-4 um in macrophages, nucleus + bar-shaped kinetoplast at right angle = Leishmania on Giemsa.
- Kinetoplast is the key differentiator from Histoplasma - Histoplasma lacks a kinetoplast on Giemsa.
- Promastigotes (elongated + anterior flagellum) are the culture/insect form - not seen in tissue from patients.
Two dark dots (nucleus + kinetoplast) in macrophage on Giemsa = Leishmania LD body. No kinetoplast = not Leishmania.