Fig. 5

The growth cycle of trypanosomatids within invertebrates. a Replication of Leishmania (Leishmania) species in the sand fly vector occurs at two locations: procyclic promastigotes replicate in the abdominal midgut and leptomonad promastigotes in the thoracic midgut. The replicative procyclic promastigote forms differentiate into elongated nectomonad promastigotes that migrate anteriorly into the thoracic midgut, where further replication in the leptomonad form occurs. Some leptomonad promastigotes attach to the cuticle-lined surface of the midgut and differentiate into haptomonad promastigotes that may act as precursors for differentiation into metacyclic promastigotes, which is the stage infective to the mammalian host. b Leptomonas are ingested in the cyst form and differentiate into the promastigote form. In the crop, the leptomonad form undergoes fission and later in the midgut and pylorus by unequal fission or budding. Cysts are formed via budding in the rectum and are passed out in the faeces as the infective form