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ESSENTIALS OF DIAGNOSIS
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ESSENTIALS OF DIAGNOSIS
Acute stage
Inflammatory lesion at inoculation site.
Fever.
Hepatosplenomegaly; lymphadenopathy.
Myocarditis.
Parasites in blood are diagnostic.
Chronic stage
Heart failure, cardiac arrhythmias.
Thromboembolism.
Megaesophagus; megacolon.
Serologic tests are usually diagnostic.
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GENERAL CONSIDERATIONS
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Chagas disease is caused by Trypanosoma cruzi, a protozoan parasite found only in the Americas; it infects wild animals and, to a lesser extent, humans from southern South America to the southern United States. 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. Control efforts in endemic countries have decreased disease incidence to about 30,000 new infections and 12,000 deaths per year. The disease is often acquired in childhood. In many countries in South America, Chagas disease is the most important cause of heart disease. The vector is endemic in the southern United States where some animals are infected, and a few instances of local transmission have been reported.
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T cruzi is transmitted by reduviid (triatomine) bugs infected by ingesting blood from animals or humans who have circulating trypanosomes. Multiplication occurs in the digestive tract of the bug and infective forms are eliminated in feces. Infection in humans occurs when the parasite penetrates the skin through the bite wound, mucous membranes, or the conjunctiva (eFigure 35–2). Transmission can also occur by blood transfusion, organ or bone marrow transplantation, congenital transfer, or ingestion of food contaminated with vector feces. From the bloodstream, T cruzi invades many cell types but has a predilection for myocardium, smooth muscle, and CNS glial cells. Multiplication causes cellular destruction, inflammation, and fibrosis, with progressive disease over decades.
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