[Transmission of chagasic infection by oral route in the natural history of Chagas disease].

The enzootic cycle of Trypanosoma cruzi in the nature is maintained for millions of years, in great part by oral route, through the ingestion of infected triatomines by edentates(Xenarthra), marsupials and primates and by carnivores eating other infected mammals. The other phases of the natural history of Chagas disease--Anthropozoonosis, Zoonosis or Anphixenosis and Zooanthroponosis are more recent. The most ancient human mummies found with DNA of T. cruzi by PCR, from northern Chile and southern Peru, dated of 9.000 years and the infection must be acquired from the forest or in the caves as an anthropozoonosis. The adaptation of triatomines to human dwellings must be started with deforestation during the agriculture cycle or for cattle raising in the last 200-300 years, when Chagas disease seat up as an endemic zoonosis. After the Triatoma infestans and the blood bank transmission ofT. cruzi were controlled in Brazil, the transmision by oral route came to be the most important and permanent transmission mechanism of the infection, as we have seen by microepidemic or outbreaks of acute Chagas disease in several regions of Brazil.