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American Trypanosomiasis

[Trypanosoma cruzi]

T. cruzi trypomastigote in a thin blood smear stained with Giemsa.

T. cruzi trypomastigote in a thin blood smear stained with Giemsa.

Trypanosoma cruzi amastigotes in heart tissue. The section is stained with H&E.

Trypanosoma cruzi amastigotes in heart tissue. The section is stained with H&E.

Causal Agent

The protozoan parasite, Trypanosoma cruzi, causes Chagas disease, a zoonotic disease that can be transmitted to humans by blood-sucking triatomine bugs.

Life Cycle

Life cycle of American Trypanosomiasis

An infected triatomine insect vector (or "kissing" bug) takes a blood meal and releases trypomastigotes in its feces near the site of the bite wound. Trypomastigotes enter the host through the wound or through intact mucosal membranes, such as the conjunctiva The number 1. Common triatomine vector species for trypanosomiasis belong to the genera Triatoma, Rhodnius, and Panstrongylus. Inside the host, the trypomastigotes invade cells near the site of inoculation, where they differentiate into intracellular amastigotes The number 2. The amastigotes multiply by binary fission The number 3 and differentiate into trypomastigotes, and then are released into the circulation as bloodstream trypomastigotes The number 4. Trypomastigotes infect cells from a variety of tissues and transform into intracellular amastigotes in new infection sites. Clinical manifestations can result from this infective cycle. The bloodstream trypomastigotes do not replicate (different from the African trypanosomes). Replication resumes only when the parasites enter another cell or are ingested by another vector. The "kissing" bug becomes infected by feeding on human or animal blood that contains circulating parasites The number 5. The ingested trypomastigotes transform into epimastigotes in the vector's midgut The number 6. The parasites multiply and differentiate in the midgut The number 7 and differentiate into infective metacyclic trypomastigotes in the hindgut The number 8.

Trypanosoma cruzi can also be transmitted through blood transfusions, organ transplantation, transplacentally, and in laboratory accidents.

Geographic Distribution

The Americas from the southern United States to southern Argentina. Mostly in poor, rural areas of Mexico, Central America, and South America. Chronic Chagas disease is a major health problem in many Latin American countries.

Clinical Presentation

The acute phase is usually asymptomatic, but can present with manifestations that include fever, anorexia, lymphadenopathy, mild hepatosplenomegaly, and myocarditis. RomaƱa's sign (unilateral palpebral and periocular swelling) may appear as a result of conjunctival contamination with the vector's feces. A nodular lesion or furuncle, usually called chagoma, can appear at the site of inoculation. Most acute cases resolve over a period of a few weeks or months into an asymptomatic chronic form of the disease. The symptomatic chronic form may not occur for years or even decades after initial infection. Its manifestations include cardiomyopathy (the most serious manifestation); pathologies of the digestive tract such as megaesophagus and megacolon; and weight loss. Chronic Chagas disease and its complications can be fatal.

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  • Page last reviewed November 29, 2013
  • Page last updated November 29, 2013
  • Content source: Global Health - Division of Parasitic Diseases and Malaria
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