Epidemiology and Etiology

T. cruzi, a member of the class Mastigophora, family Trypanisomidae, has over 100 vertebrate hosts including dogs, cats, armadillos, opossums, monkeys, and humans. Unlike other trypanosomes it does not multiply in the bloodstream, but rather lives within various tissues of the host and multiplies by binary fission. It is transmitted by reduvid bugs that ingest the trypanosome during a blood meal from a vertebrate host. The trypanosomes in turn develop in the intestines of the bug, and, while they neither enter its saliva nor are injected when the bug bites, they do pass out in its feces.

Thus the infection is transmitted when the infected insect breaks the skin to draw blood and then defecates following its meal, thereby contaminating the site of the bite. Infection can also occur when the feces is rubbed into the eyes or reaches the mucosa of the mouth, and possibly through contaminated foods as well. The trypanosomes can also be transmitted via the placenta, maternal milk, and blood transfusions.

The insect vector, which is the principal means of transmission, flourishes in huts in poor rural areas where it lives in cracks in the walls and in thatching and mats used as roofing. Cases may be few in spite of large numbers of infected bugs, if the bugs are not domesticated - that is, adapted to living in houses.

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