Chagas disease

Chagas disease (American trypanosomiasis) is an infectious disease caused by the protozoan parasite Trypanosoma cruzi (T. cruzi), which is typically transmitted by triatomine bugs of the reduviid family. Chagas disease is endemic to Central and South America and most cases that occur in the US are reported in immigrants from endemic regions. Patients present initially with fever, swelling at the site of inoculation of triatomine feces, and generalized lymphadenopathy. These symptoms resolve within a few weeks, and the patient enters an asymptomatic latent phase, which may last for 10–20 years. Eventually, 10–30% of all infected patients enter a chronic phase and develop symptoms of Chagas cardiomyopathy and/or gastrointestinal disease characterized by achalasia and progressive dilation of the colon. The disease is diagnosed by thin and thick peripheral smears in the acute phase and by serological tests in the chronic phase. Chagas disease patients are treated with the antitrypanosomal drugs benznidazole and nifurtimox. Supportive therapy is required for Chagas cardiomyopathy and gastrointestinal disease. Treatment of Chagas disease is most effective when initiated early (in the acute phase).

• Global statistics
  • Prevalence: 8–10 million infected individuals; endemic in Central and South America
  • Annual incidence: 56,000 new cases
  • Number of deaths per year due to Chagas disease: 12,000
• Prevalence in the US: > 300,000 infected individuals

Epidemiological data refers to the US, unless otherwise specified.

• Pathogen: Trypanosoma cruzi
• Route of infection
  • Vector transmission by numerous triatomine species of the reduviid family
  • Contaminated food
  • Transplacental transmission from the mother to the fetus
  • Blood transfusion, solid organ transplantation

• Incubation period: 1–2 weeks

1. Acute phase (lasts ∼ 8–12 weeks)
   • Fever, malaise, loss of appetite
   • Cutaneous manifestations
     • Chagoma: inflammatory edema at the bite site (usually in the face)
     • Romana sign: unilateral painless edema of the eyelids and periocular tissue
   • Generalized lymphadenopathy and hepatosplenomegaly
   • Rarely (∼ 1% of cases): myocarditis, meningoencephalitis
2. Indeterminate phase: Patient enters an asymptomatic latent phase.
3. Chronic phase (develops after ∼ 10–20 years)
   • Chagas cardiomyopathy
     • Conduction disorders: right bundle branch block (RBBB)
     • Biventricular dilative cardiomyopathy; → heart failure
     • Mural thrombi → stroke
   • Gastrointestinal tract
     • Damage to the submucosal and myenteric plexus → inability to relax lower esophageal sphincter and impaired gut motility → progressive dilation of the esophagus and colon
       • Megaesophagus and achalasia: dysphagia, weight loss, regurgitation
       • Megacolon: abdominal pain, chronic constipation
   • Rarely: infection of CNS tissue (esp. in immunocompromised patients)

• Confirmatory tests
  • Acute phase
    • Best initial test; : direct visualization of T. cruzi trypomastigotes in thin and thick peripheral blood smears using a Giemsa stain
    • PCR to detect T. cruzi DNA
  • Indeterminate and chronic phase: serological assays to detect IgG antibodies against T. cruzi
• Additional tests
  • Regular ECG monitoring every 6–12 months
    • Patients with symptoms or ECG signs of Chagas cardiomyopathy → see “Diagnostics of dilated cardiomyopathy”
  • Patient with symptoms of GI involvement: barium radiography, endoscopy, and manometry (also see “Diagnostics” in achalasia)

Chagas disease should be suspected in immigrants from endemic regions!