Microscopy

Trypansoma cruzi trypomastigotes are the only stage found in the blood of an infected person.  Motile circulating trypomastigotes are readily seen on slides of fresh anticoagulated blood in acute infection but are rarely detectable by microscopy in chronic T. cruzi infection.  A typical trypomastigote has a large, subterminal or terminal kinetoplast, a centrally located nucleus, an undulating membrane, and a flagellum running along the undulating membrane, leaving the body at the anterior end.  Trypanosomes measure from 12 to 30 µm in length.  Trypomastigotes may be seen in cerebrospinal fluid (CSF) in central nervous system infections; also the amastigote stage parasite may be seen in histopathology specimens from affected organs.

A	B

A, B: T. cruzi trypomastigotes in a thick blood smear stained with Giemsa.

C	D

C, D: T. cruzi trypomastigotes in thin blood smears stained with Giemsa.  Note the typical C-shape of the trypomastigote that characterizes T. cruzi in fixed blood smears.

E	F

E: T. cruzi trypomastigote in cerebrospinal fluid (CSF) stained with Giemsa.
F: T. cruzi amastigotes in heart tissue.  The section is stained with hematoxylin and eosin (H & E).