Trypanosomiasis, American (Chagas Disease)

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

• Transmitted by reduviid (triatomine) bugs infected by ingesting blood from animals or humans who have circulating trypanosomes

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

• Transmission can also occur by blood transfusion, organ or bone marrow transplantation, congenital transfer, or ingestion of food contaminated with vector feces

• T cruzi has a predilection for myocardium, smooth muscle, and central nervous system (CNS) glial cells

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

• As disease progresses over decades, multiplication of parasite causes

  • Cellular destruction

  • Inflammation

  • Fibrosis

Demographics

• An estimated 6–7 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 30,000 new infections and 12,000 deaths per year

• An estimated 288,000 infected persons live in the United States

• A few instances of local transmission have been reported in the southern United States

• The disease is often acquired in childhood

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 ...