A quasi-experimental epidemiological model for evaluating public health programmes: efficacy of a Chagas disease control programme in Brazil.

Reported is the assessment of a model to evaluate the efficacy of public health programmes, using the example of the Chagas Disease Control Programme in the State of Minas Gerais, Brazil. The reduction in Trypanosoma cruzi infection rates in areas where interventions had been carried out for 5 years and 10 years, respectively, were compared with those where there had been no intervention (controls). A random sample of 470 households was selected and blood samples were collected from the 2354 inhabitants, 854 (36.3%) of whom were born after the start of the control programme. The data routinely collected by the control programme were also analysed to correlate the results with the incidence of T. cruzi infection. The programme efficacy was estimated by comparing the infection rates found in the study with those published by the Chagas Disease Serological Study (1975-80). Cross-sectional comparison of the data for the age group 2-6 years indicated that there had been a reduction in T. cruzi infection incidences of 94.7%, 63.2%, and 65%, respectively, in areas where interventions had been carried out for 10 years, 5 years, and in the control areas. Cohort comparison indicated, however, that the reduction (52.6%) occurred only in the intervention-10 area.