Ultrastructure of amastigotes of Leishmania donovani in the bone marrow of a dog.

Visceral leishmaniasis was diagnosed in a dog which had been in Spain for 4 years before being brought to Florida. A bone marrow aspirate from the dog was examined by electron microscopy. Phagocytized amastigotes by macrophages had an electron-dense plasma membrane and contained ribosomes, rough endoplasmic reticulum, a well-developed Golgi apparatus, an intracellular flagellum, lipid, a kinetoplast, a row of microtubules immediately beneath the cell membrane, and a nucleus with marginated chromatin. Mean diameter and microtubule number of the dog isolate were similar to those reported for Leishmania donovani amastigotes of human origin. Plasma cells were congregated in the vicinity of parasitized macrophages.