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94 CHAPTER 4

MICROSCOPIC DIAGNOSTIC

FEATURE

General
Classification—Sporozoan

Organism Trypanosoma cruzi
Specimen Required Blood, tissue, or
serological evidence
of infection
Stage Trypomastigote
forms in circulatory
system are diagnostic
Source: Centers for Disease Control and Prevention (CDC) Shape gotes average 20 μm
Amastigotes are 1.5–
Size
4.0 μm; trypomasti-
in length
Oocysts somewhat
oval; “U”- or “C”-
shaped trypomasti-
gotes in blood smear
Motility
Flagellar motil-
trypanomastigotes
Large red nucleus
Nucleus(i) ity of invading
FIGURE 4-13 Chagas’s disease manifested as an acute with dark-stained
infection with swelling of the right eye rodlike kinetoplast in
Giemsa-stained
specimen
the length of the organism, extending as a free flagellum Cytoplasm Smooth
to the anterior portion of the organism.
Other Features Tissue cysts contain
large numbers of
Treatment and Prevention slow-growing
trophozoites
Drugs currently available for the treatment of trypanoso-
miasis may be to some extent toxic. Melarsoprol is usu-
ally administered to those with more advanced stages of two distinctly different clinical pictures. The diseases
the disease. Pentamidine is sometimes prophylactically are caused by infection with either of two subspecies of
used during epidemics but the key to prevention is the trypanosomes, Trypanosoma brucei gambiense, which
control of the vectors involved in transmitting the organ- causes Gambian (West Africa Sleeping Sickness) or
ism and reconstruction and repair of homes to prevent chronic sleeping sickness, and T. brucei rhodesiense,
the entry of triatomid insects. which causes Rhodesian (Eastern African Sleeping Sick-
ness) or acute sleeping sickness. The trypanosomes mul-
AFRICAN TRYPANOSOMIASIS tiply in the blood and are taken up by tsetse flies when
they feed on an infected human or other domesticated or
African trypanosomiasis is spread by the tsetse fly (there wild mammal. The life cycle within the tsetse fly includes
are at least twenty-two species of the insect) in two sepa- a period in which multiplication and development re-
rate geographic locations of Africa and demonstrate sults during the formation of infective trypanosomes in