Friday 23 April 2004
Trypanosoma cruzi is endemic in Central and South America with 16-18 million infected persons and 100 million persons living in conditions at risk of infection.
Persons become infected by the deposition of trypanosome-contaminated feces by infested triatomid bugs and its subsequent autoinoculation into the dermis or onto mucous membranes (e.g., the conjunctiva, where inflammation may be recognized as Romaña sign).
Other modes of infection include infected blood transfusions and mother-to-fetus. Trypanosoma cruzi is maintained in natural cycles involving more than 100 species of wild and domestic mammals including opossums, dogs, wood rats, armadillos, raccoons, and cats from the southern US to central Argentina.
Infected animals maintain lifelong parasitemia, an enormous reservoir of the agent. Mainly known as a chronic infection, Chagas’ disease can cause a lethal disease, particularly in infants and young childern, ususally owing to acute myocarditis and more rarely meningoencephalitis. There have been five patients with autochthonous Chagas’ disease diagnosed in the US, four of whom were children ages 2-3 weeks to 18 months.
The definitive diagnosis of American trypanosomiasis is made by identifying the protozoal parasites. Highly motile circulating trypomastigotes can frequently be detected in a wet preparation of anticoagulated blood or buffy coat or in a Giemsa-stained smear.
In immunocompromised patients including those with AIDS, the diagnosis of acute Chagas’ disease may be facilitated by microscopic examination of bone marrow, lymph node aspirate, CSF, or pericardial fluid.
Cultivation in special liquid medium or xenodiagnosis, although not widely available and requiring weeks to complete, are more sensitive than microscopy. Polymerase chain reaction detection of trypanosomal DNA is highly sensitive and specific if performed properly.
Chagas disease (american trypanosomiasis)
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