Trypanosoma cruzi - Chagas Disease

Chagas disease or American trypanosomiasis is caused by Trypanosoma cruzi, a protozoan transmitted by infected Triatominae insects. Diagnosis is generally made by testing with at least two different serologic tests; IgG confirms chronic disease.

Diagnosis

Indications for Testing

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

Laboratory Testing

Trypanosomiasis diagnosis (CDC, 2014)
Acute phase (first 60-90 days)
- Direct detection of parasites on blood smear (Giemsa stain)
- IgM may be useful in acute infection
- Polymerase chain reaction (PCR) is very sensitive when available
Nonacute (chronic) phase (>90 days)
- IgG confirms chronic disease – by indirect fluorescent antibody (IFA), enzyme-linked immunosorbent assay (ELISA), or indirect hemagglutination antibody (IHA)
  - World Health Organization (WHO) recommends at least two tests to confirm disease
- Cross-reactivity with Leishmania spp may occur
- PCR requires further validation

Differential Diagnosis

Muscular disease
- Trichinella spiralis infection
- Inflammatory myopathies
Cardiomyopathy
- High-output failure
  - Anemia
  - Beriberi
  - Paget disease
  - Hyperthyroidism
- Acute rheumatic fever
- Valvular disease
- Congenital heart disease
- Acute myocarditis
Megaesophagus
- Achalasia
- Strictures
- Esophageal cancer
Megacolon
- Hirschsprung disease
- Diabetic gastroenteropathy
- Colonic stricture
- Systemic sclerosis
- Amyloidosis
Neurologic disease
- Myotomic dystrophy
- Parkinson disease
- Chronic opiate ingestion
- Severe hyperthyroidism

Background

Epidemiology

Prevalence
- U.S. – almost exclusively found in immigrants from Central and South America
- Worldwide – 16-18 million individuals infected
Transmission
- Triatominae vector species (kissing bug)
- Maternal transplacental transfer (congenital)
- Blood transfusion from infected donor
- Organ transplantation
- Ingestion of contaminated food/water (rare)

Organism

The genus Trypanosoma contains many species of protozoans
- Only three cause human disease – T. cruzi, T. brucei gambiense, and T. brucei rhodesiense
- Vectorborne from the reduviid 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
  - Romaña sign – unilateral painless edema of palpebral and periocular tissues
- Initial signs include malaise, fever, anorexia, rash, and edema
- Acute myocarditis in small percentage of cases
- Indurated area of erythema and swelling (chagoma) may indicate parasite entry site
- Frequently undetected at this stage
Chronic phase
- May manifest decades later
- Cardiomyopathy with arrhythmia
  - ~20-30% of patients (Bern, 2015)
  - Earliest sign is conduction defects – patient usually asymptomatic
  - Symptoms of biventricular failure – peripheral edema, hepatomegaly
  - ~60% experience sudden cardiac death
- Digestive system complications
  - Megacolon
  - Ranges from mild achalasia to megaesophagus
Congenital disease
- Highest risk for infection when maternal parasitemia is high during acute phase
- Prematurity, hepatosplenomegaly, meningitis/encephalitis
Immunocompromised hosts
- Organ transplant recipients – more severe clinical spectrum that can include acute myocarditis and congestive heart failure
- Immunocompromised patient with reactivation – most common presentations are meningoencephalitis, brain abscess, and acute myocarditis