Leishmania Life Cycle

1. Leishmaniasis is transmitted by the bite of infected female phlebotomine sandflies. During a blood meal, the sandflies inject metacyclic promastigotes (the infective stage) from their proboscis.

2. Promastigotes are phagocytized by macrophages and other mononuclear phagocytic cells.

3. In these cells, promastigotes transform into amastigotes (the tissue stage).

4. Amastigotes multiply by simple division and infect other mononuclear phagocytic cells.

5–6. During a blood meal on an infected host, sandflies become infected by ingesting macrophages infected with amastigotes.

7. In the midgut of the sandflies, amastigotes transform into promastigotes.

8. There, they multiply, develop, and migrate to the proboscis.