Nested case-control study in a serological survey to evaluate the effectiveness of a Chagas disease control programme in Brazil

Abstract

OBJECTIVE: To identify risk factors associated with Trypanosoma cruzi infections in areas under surveillance in the State of Minas Gerais, Brazil. METHODS:A model using a nested case-control design incorporated within a serological survey of schoolchildren which was employed to evaluate the effectiveness of the Chagas disease control programme. FINDINGS:In a sample of 40 374 schoolchildren (aged 7-14 years) surveyed, 16 children tested positive for T. cruzi antibody (by indirect immunofluorescence and indirect haemagglutination). In the case-control study, each case was randomly matched to three seronegative controls (classroom and age + 1 year). Compared to controls, T. cruzi-seropositive children were more likely to have a seropositive mother (odds ratio (OR) = 6.8; 95% confidence interval (CI) = 0.71-63.9) or a seropositive family member (OR = 8.6; 95% CI = 1.0-75.5). CONCLUSION:Use of the nested case-control model in a sero-epidemiological survey to evaluate risk factors for T. cruzi transmission was adequate for assessing the effectiveness of a Chagas disease control programme.

Keywords

• Chagas disease/prevention and control
• Child
• Program evaluation/methods
• Risk factors
• Logistic models
• Seroepidemiologic studies
• Case-control studies
• Brazil