Chagas Disease - Trypanosoma cruzi

Diagnosis

Indications for Testing

  • Residency in endemic area
  • Recent travel in endemic area
  • Cardiomyopathy or prototypical gastrointestinal disease without obvious etiology

Laboratory Testing 

  • CDC trypanosomiasis diagnosis 
  • Acute phase (first 60-90 days)
    • Direct detection of parasites on blood smear (Giemsa stain)
    • IgM may be useful in acute infection
  • Chronic phase (>90 days)
    • IgG confirms chronic disease – by IFA, ELISA, IHA
      • WHO recommends ≥2 tests to confirm disease
    • Cross-reactivity with Leishmania spp may occur
    • PCR requires further validation

Differential Diagnosis

Clinical Background

Chagas disease or American trypanosomiasis is caused by Trypanosoma cruzi, a protozoan transmitted by infected Triatominae insects.

Epidemiology

  • Prevalence
    • In U.S., almost exclusively in immigrants from Central and South America
    • 16-18 million individuals infected worldwide; roughly 50,000 deaths annually from chronic Chagas disease
  • Transmission
    • Common Triatominae vector species (kissing bugs) for trypanosomiasis belong to the genera Triatoma, Rhodnius, and Panstrongylus
    • Maternal transplacental transfer (congenital)
    • Blood transfusion from infected donor
    • Organ transplantation
    • Ingestion of contaminated water (rare)

Organism

  • The genus Trypanosoma contains many species of protozoans
    • Only 3 cause human disease – T. cruzi, T. brucei gambiense, and T. brucei rhodesiense
    • Vector-borne from the reduviid insect, Triatoma gerstaeckeri, and others
      • Exposure to feces deposited on skin by infected bugs

Clinical Presentation

  • Acute phase
    • Mild symptoms occur for 2 weeks to 3 months
    • Initial signs include malaise, fever, anorexia, rash, and edema
    • Acute myocarditis in 5% of cases
    • Most recognized marker is Romaña sign – unilateral painless edema of palpebral and periocular tissues
    • Indurated area of erythema and swelling (chagoma) may indicate parasite entry site
    • Frequently undetected at this stage
  • Indeterminate phase
    • Begins after acute phase
    • Usually asymptomatic, although symptoms of cardiomyopathy may be present
  • Chronic phase
    • May manifest decades later (~30% of those infected)
    • Cardiomyopathy with arrhythmia
      • Symptoms of biventricular failure – peripheral edema, hepatomegaly
      • ∼60% experience sudden cardiac death
    • Digestive system complications
      • Megacolon
      • Megaesophagus
  • Congenital disease
    • Highest risk with high maternal parasitemia during acute phase
    • Prematurity, hepatosplenomegaly, meningitis/encephalitis

Treatment

  • Antiprotozoal therapy is effective if patient diagnosed in acute phase

Indications for Laboratory Testing

  • Tests generally appear in the order most useful for common clinical situations
  • Click on number for test-specific information in the ARUP Laboratory Test Directory
Test Name and Number Recommended Use Limitations Follow Up
Trypanosoma cruzi Antibody, IgG 0051076
Method: Semi-Quantitative Immunoassay
Preferred test if exposure to T. cruzi is suspected and Chagas disease symptoms exist (chronic phase test)

Travel history required

If test results equivocal, repeat testing in 10-14 days

Trypanosoma cruzi Antibody, IgM 0051075
Method: Semi-Quantitative Indirect Fluorescent Antibody

Detect antibodies specific to T. cruzi in patients with congruent clinical history (acute phase test)