[Course of serologic positivity to Chagas disease in a rural community in Brazil].

In order to assess the evolution of seropositivity for Chagas' disease in the rural community of Cássia dos Coqueiros, in São Paulo state, we compared two cross-sectional studies performed at that site in 1971-1972 and in 1989-1991. In the first survey the complement fixation test was used to determine seropositivity for the disease. In this study, the total prevalence of Chagas' disease was found to be 16.6%, with values ranging from 2.9 to 61.9% (in the 10-19 and 50-59 year age groups, respectively). In the 1989-1991 study, in which indirect immunofluorescence was used, the total prevalence dropped to 10.1%, with a minimum of 0.4% (in the 10-19 year age group) and a maximum of 44.8% (in persons over 60 years of age). Among subjects born in Cássia dos Coqueiros, the 1989-1991 study showed seropositivity after age 38, with only one exception (a 24-year-old man). The drop in the seropositivity index for Chagas' disease in Cásia dos Coqueiros during the period under study can be partially attributed to socioeconomic factors, such as improved living conditions and the progressive abandonment of rural areas. Thus, our results point to the spraying of households with residual insecticides, which began in 1950, as the pivotal factor in the fight against triatomine bugs and in disease control. These results suggest that transmission may have been interrupted as early as the latter part of 1954 and later consolidated as a result of improved socioeconomic conditions and the elimination of Triatoma infestans from the study area.