Chagas disease: 100 years after its discovery. A systemic review.
Although Chagas disease was only discovered in 1909, it began millions of years ago as an enzootic disease among wild animals. Its transmission to man began accidentally as an anthropozoonosis when mankind invaded wild ecotopes. Endemic Chagas disease became established as a zoonosis over the last 200-300 years through deforestation for agriculture and livestock rearing and adaptation of triatomines to dwellings and to humans and domestic animals as food sources. When T. cruzi is transmitted to man, it invades the bloodstream and lymphatic system and lodges in muscle and heart tissue, the digestive system and phagocytic cells. Through this, it causes inflammatory lesions and an immune response, particularly mediated by CD4(+), CD8(+), IL2 and IL4, with cell and neuron destruction and fibrosis. These processes lead to blockage of the heart's conductive system, arrhythmias, heart failure, aperistalsis and dilatation of hollow viscera, especially the esophagus and colons. Chagas disease is characterized by an acute phase with or without symptoms, with (or more often without) T. cruzi penetration signs (inoculation chagoma or Romaña's sign), fever, adenomegaly, hepatosplenomegaly and patent parasitemia; and a chronic phase: indeterminate (asymptomatic, with normal electrocardiogram and heart, esophagus and colon X-rays) or cardiac, digestive or cardiac/digestive forms. There is great regional variation in the morbidity caused by Chagas disease: severe cardiac or digestive forms may occur in 10-50%, and indeterminate forms in the remaining, asymptomatic cases. The epidemiological and control characteristics of Chagas disease vary according to each country's ecological conditions and health policies.