Clinical evolution and morbi-mortality in Chagas disease

The knowledge firstly achieved by CarlosChagas and his colleagues of the Instituto OswaldoCruz, increased with all those acquired to date, al-low us to outline the general scheme (modifiedfrom Dias & Coura 1997) of American trypanoso-miasis natural history (Figure).The knowledge of this natural history makesmore comprehensible the clinical evolution of thedisease, as it will be demonstrated by the reportersof the subject.The Chagas Disease Control Campaign, to-gether with other conditions, has contributed in adecisive way for the significant reduction of thenumber of new cases of the disease. Nevertheless,millions of chagasic individuals still live in ourcountry as well as in other ones of Latin America(Moncayo 1993, Schmunis 1997, Dias & Coura1997). Only this would be enough to justify theconcern with morbidity and mortality due to Ameri-can trypanosomiasis.In addition, the current data about morbidity(analyzed either by the number of individuals whoacquire the disease or by the number of cases inwhich trypanosomiasis has arisen), as well as thecoefficients or rates of mortality allow the under-standing of the severe medicosocial problems con-tinuously generated by the endemic.In the other hand, the prophylatic and thera-peutic measures can explain the significant reduc-tion of morbility and mortality rates in Chagas dis-ease (CD) acute phase in the last years, as it maybe confirmed by comparing Chagas references(1910, 1916) and Chagas and Villela (1922) withthose of Dias (1955), Ferreira (1986) and Dias andCoura (1997).In order to analyse the morbity and mortality inchronical CD, two facts must be initially remem-bered: first, in the chronic phase of American trypa-nosomiasis, the main lesions are situated in the heartand digestive tract; second, the digestive form ofthe disease was characterized only in the 50s(Rezende 1956). This last fact may explain the lackof references on digestive manifestations inchronical CD in the first half of century (Chagas1910, Chagas & Villela 1922), what reflects on com-parative analyses, specially regarding morbidity.In conclusion, it is clear since the beginning ofthe studies on CD that cardiac alterations are themain responsible for morbidity and mortality.Longitudinal studies as those carried out ini-tially in Bambui, State of Minas Gerais, Brazil, fol-lowed by other more recent ones as those ofMacedo (1973) and Dias (1982), allow us to con-clude that only half of the individuals infected withT. cruzi show, in the course of their lives, clinicalmanifestations of CD; among those, only about50% die as a direct or indirect result of the infec-tious course. Mortality is generally high amongchagasic individuals who develop chronic cardi-opathy, mainly when cardiac failure and/or severearrythmias occur. Grossly, it means that 25% ofthe chagasic individuals (which correspond to350,000 people in Brazil) are bound to die becauseof CD. The death official registry service in Brazilindicates that the mortality due to disease is about6,000 deaths/year, prone to decrease in the last de-cade. In Latin America, Moncayo (1993) evalu-ates that 45,000 yearly deaths are due to CD.In the micro-regions of major endemicity, thedeath rate due to CD among adult individuals mayreach 200 per 100,000 inhabitants or more. Theserates are surely underdimensioned since that a sig-nificative number of deaths due to chronicalchagasic cardiopathy are registered as either dueto non defined causes or lack of medical care ordue to other cardiopathies.Data from the World Bank in 1993 show theenormous social burden as a consequence of CD.This burden is significantly greater than that pro-duced by other tropical diseases prevalent in theAmericas. Malaria, schistosomiasis, leishmaniasis,filariasis, oncocercosis and leprosy produce all to-