Leishmania protozoa and blood cells. Coloured scanning electron micrograph (SEM) of Leishmania sp. parasitic protozoa with red blood cells (erythrocytes, red). Leishmania is a genus of trypanosomatid protozoa, and is the parasite responsible for the disease leishmaniasis. A variety of different morphological forms appear in the life cycles of trypanosomatids. Shown here are the promastigote (leptomonad) form, the common morphology found in the insect host. Magnification: x 4670, when printed 10 centimetres wide.