Summary of results from the national surveys

This article aims to correlate the main results of three large national surveys on Chagas disease (entomologic, seroprevalence and electrocardiographic) carried out in Brazil from late 1970's to early 1980's, which served as baseline for definition of the control measures adopted in the country. The proportion of infected people was much higher in areas where Triatoma infestans, the most efficient vector of Chagas disease among the five principal species involved in transmission at that time, was predominant. Similar result was observed in places where Triatoma sordida was dispersed, mainly in the country's central region, which corresponds to its native area. This finding is due to the coincidence observed in the geographic distribution of both vectors, since T. sordida is not considered to play an important role in transmission. In the Northeastern semi-arid, endemic area for Triatoma brasiliensis and Triatoma pseudomaculata, rates of human infection were much lower, although both vectors may have some relevance in the maintenance of the disease. As for areas with Panstrongylus megistus, human infection varied according to the levels of domiciliation. Whenever domiciled, like in the humid northeastern coastal area, its involvement in transmission can be clearly demonstrated. In some parts of Bahia State it represented the exclusive vector of the disease. Based upon the results of the seroprevalence survey an electrocardiographic study was carried out in 11 Brazilian states, which showed marked differences in the presence of cardiac alterations when comparing different areas of the country.