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Key Features

Essentials of Diagnosis

Acute stage

  • Inflammatory lesion at inoculation site

  • Fever

  • Hepatosplenomegaly

  • Lymphadenopathy

  • Myocarditis

  • Parasites in blood is diagnostic

Chronic stage

  • Heart failure, cardiac arrhythmias

  • Thromboembolism

  • Megaesophagus

  • Megacolon

  • Serologic tests are usually diagnostic

General Considerations

  • Caused by Trypanosoma cruzi, a protozoan parasite

  • Parasite infects wild animals and, to a lesser extent, humans from southern South America to southern United States

  • T cruzi has a predilection for myocardium, smooth muscle, and CNS glial cells

  • In many countries in South America, Chagas disease is the most important cause of heart disease

  • Infection occurs when parasite penetrates skin through bite wound, mucous membranes, or conjunctiva

  • As disease progresses over decades, multiplication of parasite causes

    • Cellular destruction

    • Inflammation

    • Fibrosis

Demographics

  • An estimated 8–10 million people are infected, mostly in rural areas, with the highest national prevalence in Bolivia, Argentina, Paraguay, Ecuador, El Salvador, and Guatemala

  • In endemic countries, incidence has decreased to about 40,000 new infections and 12,500 deaths per year

  • In the United States, only a few instances of local transmission have been reported

Clinical Findings

Symptoms and Signs

  • Up to 70% of persons remain asymptomatic

Acute stage

  • Seen principally in children

  • Lasts 1–2 months

  • The earliest findings are at the inoculation site

    • In the eye—Romaña sign (unilateral edema, conjunctivitis, lymphadenopathy) or

    • In the skin—a chagoma (swelling with local lymphadenopathy)

  • Subsequent findings include

    • Fever

    • Malaise, headache

    • Mild hepatosplenomegaly

    • Generalized lymphadenopathy

  • Acute myocarditis and meningoencephalitis are rare but can be fatal

Latent stage (indeterminate phase)

  • This asymptomatic stage may last for life, but symptomatic disease develops in 10–30% of infected individuals, commonly many years after infection

Chronic stage

  • Generally manifests as abnormalities in cardiac and smooth muscle

  • Cardiac disease includes

    • Arrhythmias

    • Heart failure

    • Embolic disease

  • Smooth muscle abnormalities lead to megaesophagus and megacolon with

    • Dysphagia

    • Regurgitation

    • Aspiration

    • Constipation

    • Abdominal pain

  • These findings can be complicated by superinfections

  • Latent Chagas disease may reactivate in immunosuppressed patients; findings include brain abscess and meningoencephalitis

Differential Diagnosis

  • Acute stage: malaria, rheumatic fever, African trypanosomiasis

  • Myocarditis due to other causes, eg, coxsackievirus, drugs

  • Coronary artery disease

  • Toxic megacolon due to inflammatory bowel disease or Clostridioides difficile–associated colitis

Diagnosis

Laboratory Tests

Acute stage

  • Evaluation of fresh blood or buffy coats may show motile trypanosomes

  • Fixed preparations may show Giemsa-stained parasites

  • Concentration methods increase diagnostic yields

  • Trypanosomes may be identified in lymph nodes, bone marrow, or pericardial or spinal fluid

  • Molecular tests are ...

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