In humans, T. cruzi is found as both an intracellular form, the amastigote, and as a trypomastigote form in the blood. The vector for Chagas' Disease, a "true bug" (Hemiptera) such a Triatoma,
ingests amastigotes or trypomastigotes when it feeds. In the vector the parasite reproduces asexually as epimastigotes, and metacyclic trypomastigotes are found in the vector's hindgut. The vector defecates on the host's skin at the same time that it feeds, and the metacyclic trypomastigotes enter the host's body, most often by being "rubbed in" to the vector's bite or the mucous membranes of the eye, nose, or mouth. The local inflammation caused by the entry of T. cruzi is called chagoma. Chagoma of the eye, Romaña' sign, is seen in 90 % of patients diagnosed as recently infected.
In the human host, Chagas' Disease affects primarily the nervous system and heart. Chronic infections result in various neurological disorders, including dementia, megacolon, and mega-oesophagus, and damage to the heart muscle. Left untreated, the disease is often fatal.
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X-rays of two patients suffereing from the late stage of Chagas' disease, one with megacolon and the other with a severeweakening and widening of the hart muscle.
