Clinical Features:
A local lesion (chagoma, palpebral edema) can appear at the site of inoculation.  The acute phase is usually asymptomatic, but can present with manifestations that include fever, anorexia, lymphadenopathy, mild hepatosplenomegaly, and myocarditis.  Most acute cases resolve over a period of 2 to 3 months into an asymptomatic chronic stage.  The symptomatic chronic stage may not occur for years or even decades after initial infection.  Its manifestations include cardiomyopathy (the most serious manifestation); pathologies of the digestive tract such as megaesophagus and megacolon; and weight loss.  Chronic Chagas disease and its complications can be fatal.

Laboratory Diagnosis:
Demonstration of the causal agent is the diagnostic procedure in acute Chagas disease.  It almost always yields positive results, and can be achieved by:

• Microscopic examination: a) of fresh anticoagulated blood, or its buffy coat, for motile parasites; and b) of thin and thick blood smears stained with Giemsa, for visualization of parasites.
• Isolation of the agent by: a) inoculation into mice; b) culture in specialized media (e.g. NNN, LIT); and c) xenodiagnosis, where uninfected reduviid bugs are fed on the patient's blood, and their gut contents examined for parasites 4 weeks later.

Note: In certain circumstances, investigational molecular diagnostic tools, such as PCR, may be useful.

Diagnostic Findings

• Microscopy
• Antibody detection is the diagnostic method of choice in chronic Chagas disease.

Treatment:
Medication for Chagas disease is usually effective when given during the acute stage of infection.  The drugs of choice are benznidazole or nifurtimox (under an investigational New Drug Protocol from CDC's Drug Service).  In the chronic stage, treatment involves managing the clinical manifestations of the disease, e.g., pacemaker for heart block; the decision about whether to use antiparasitic therapy should be individualized in consultation with an expert.  See recommendations in The Medical Letter for complete information.