In tissue smears, which finding is characteristic of Leishmania infection?

• A. Amastigotes within macrophages
• B. Erythrocyte parasitic forms
• C. Oocysts in stool
• D. Flagellated trophozoites in urine

Answer: (A)

Leishmania infection in tissue smears is identified by intracellular amastigotes inside macrophages, known as Leishman-Donovan bodies. In the human host, the parasite takes a nonflagellated amastigote form that reproduces within macrophages of the reticuloendothelial system (like bone marrow, spleen, liver, or lymph nodes). Under light microscopy with a stain such as Giemsa, you see small oval organisms within the cytoplasm of macrophages, each with a nucleus and a kinetoplast. This intracellular localization within macrophages is the hallmark seen in tissue samples. Other options reflect organisms or stages from different parasites—red blood cell parasitism is typical of malaria, oocysts in stool point to intestinal coccidia, and flagellated trophozoites in urine suggest organisms like Trichomonas—not Leishmania.