Page 453 - Review of Medical Microbiology and Immunology ( PDFDrive )
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PART VI Parasitology
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FIGURE 52–8
Trypanosoma cruzi. Life cycle. Right side of figure describes the stages within the human (blue arrows). Humans are
infected at step 1 when triatomine (reduviid) bug bites human and defecates at bite site. Trypomastigotes in feces enter bite wound.
Amastigotes form within cells, especially heart muscle and neural tissue. Reduviid bug is infected at step 5 when it ingests trypomastigotes
in human blood. Left side of figure describes the stages within the reduviid bug (red arrows). (Source: Dr. Alexander J. da Silva and Melanie Moser,
Centers for Disease Control and Prevention.)
Chagas’ disease has occurred in the United States in
recipients of either blood transfusions or organ transplants
progress to the chronic form with myocarditis and megaco-
from infected donors. The organism can also be transmit-
lon. Death from chronic Chagas’ disease is usually due to
cardiac arrhythmias or congestive heart failure.
ted congenitally from an infected mother to the fetus across
the placenta.
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Clinical Findings
Acute disease is diagnosed by demonstrating the presence
The acute phase of Chagas’ disease consists of facial edema
of trypomastigotes in thick or thin films of the patient’s
and a nodule (chagoma) near the bite, coupled with fever,
blood. Both stained and wet preparations should be exam-
ined, the latter for motile organisms. Because the trypomas-
lymphadenopathy, and hepatosplenomegaly. A bite around
the eye can result in unilateral palpebral swelling called
tigotes are not numerous in the blood, other diagnostic
methods may be required, namely, (1) a stained preparation
Romaña’s sign. The acute phase resolves in about 2 months.
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