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[Trypanosoma cruzi]

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: T. cruzi trypomastigote in a thin blood smear stained with Giemsa.
B: Higher magnification of Figure A, T. cruzi.

C	D

C: T. cruzi trypomastigote in a thin blood smear stained with Giemsa.  Note the more anterior location of the nucleus.
D: Higher magnification of Figure C, T. cruzi.

E	F

E: T. cruzi trypomastigote in a thin blood smear stained with Giemsa.
F: Higher magnification of Figure E, T. cruzi.