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Lab studies:
In practice, the diagnosis of the acute phase
of infection or in patients who are immunosupressed
is based on the parasitological diagnosis, whereas
the diagnosis of the chronic infection and test
for the selection of blood donors essentially
depend on serology results.
Parasitological diagnosis.
The best and simplest way to make the direct
diagnosis of acute disease is by microscopic of
a drop of fresh anticoagulated blood (5ml), allowing
the observation of the rapid movements of live
T Cruzi trypomastigotes. Examination of at least
100 microscopic fields is necessary before concluding
the absence of parasites.
If repeated fresh blood examinations fail to
reveal evidence of infection, alternative direct
methods can be used in order to concentrate the
parasites (mainly microhematocrit and Strout methhods).
Indirect methods allow multiplication of parasites
from the collected samples into the insect vector
(xenodiagnostic) or in culture medium.
The xenodiagnostic method consist of feeding
40 laboratory-reared and uninfected Triatominae
with blood from the patient under examination.
Insects can be put either directly in contact
with the patients skin or with anticoagulated
blood through a thin latex membrane. The intestinal
contents of the insects are examined 30-60 days
later to observe for metacyclic trypomastigotes.
For many reason, indirect parasitological methods
are progressively becoming less popular. They
are less sensitive than other tests (direct methods
in the acute phase and serology in chronic infection).
The material necessary to performs these test
is not commercially available. Such examinations
are long and require highly specialized personnel.
The results are available only1-6 months after
the test. Therefore , the indirect parasitological
methods are reserved for use at specialized centers
to confirm the diagnosis in rare cases of serologically
doubtful results, to evaluate new drugs.
Immunological diagnosis.
Three commercially available serological test
are used routinely for investigation of T.
cruzi-specific antibodies: indirect hemaglutination,
immunoflourescence (IFI), and enzyme-linked immunosorbent
assay (ELISA) using crude parasite antigens.
Molecular diagnosis.
Various polymerase chain reaction (PCR) procedures
have been described that use specific primers
to detect T.
cruzi Kinetoplastic or nuclear DNA.
Imaging Studies.
Chest radiography.
• In cases of acute or chronic chagasic
cardiopathy, global heart enlargement is observed.
• In the terminal phase of the congestive
heart failure, patients have evidence of congested
lung fields.
Radiographic contrast study of esophagus:
Serial radiographs of the esophagus at different
times after contrast ingestion allow classification
of patients into 1 of 4 evolutive stages of the
chagasic esophagopathy .
Radiographic study of the colon
• Findings from simple abdominal radiographs
can be useful in cases of occlusion.
• Findings from an air-contrast study barium
enema help delineate abnormalities in the colon.
• Radiographic contrast studies of the colon
must be performer using low-pressure contrast
to prevent a rupture of the thin wall of the megacolon.
Ultrasound
Ultrasound images are useful to detect an aplical
left ventricular aneurysm, intracardiac thrombi,
a hypokinesia of the posterior basal or septal
cardiac walls, or study ventricular dysfunctions.
Other Tests
Other test used are the electrocardiogram and
the esophageal endoscopy.
Source of Information
• Yves Carlier, MD, MSc.
Chagas Disease (American Trypanosomiasis)
eMedicine.com, Inc.
http://www.emedicine.com/med/topic327.htm
Used with permission from eMedicine.com,
Inc., 2004. Carlier Y, Luquetti AO, Dias JCP, Truyens
C, et al. Chagas Disease (American Trypanosomiasis).
eMedicine Journal [serial online]. 2004. Available
at: http://www.emedicine.com/med/topic327.htm. Accessed
Date (i.e., January 19, 2004).
More Information
• The Chagas Disease
• Historical Review
• Dr.
Carlos Justiniano Riveiro Chagas (1879-1934)
• Dr.
Salvador Mazza (1886 -1946)
• Dr.
Mario Fatala Chabén (1936-1962)
• Dr.
Oswaldo Cruz (1872-1917)
• Medical
Information
• Epidemiology
• Mortality
• Race,
sex and age.
• Modes
of Transmission
• Pathophysiology
• Clinical
Information
• Diagnostic
• Other
Medical Information
• Prevention
and Control
• Frequently Asked Questions
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