Emprego de quatro exames imunológicos na determinaçäo da prevalência da doença de Chagas nos garis do Serviço de Limpeza Urbana do Distrito Federal / The use of four immunological tests to determine the prevalence of Chagas' disease in street cleaners of the Urban Cleaning Service of the Federal District

Seropositivity for Trypanosoma cruzi infection was studied in 368 street-sweepers of the SLU, Federal District, Brazil, with the aid of haemaglutination, immunofluorescence and, also, a delayed-type skin test to the parasite T12E antigen. It showed 32.1 per cent, 42.1 per cent and 38.6 per cent positive results, respectively for each assay. Among these, however, only 47 per cent were positive with each of three exams performed. In addition, 19.7 per cent were positive with two out of three exams performed. The remaining 33.3 per cent sera yielded one positive result out of three exams employed and were submitted to the immunoblot assay. This analysis confirmed 3 cases (37.5 per cent) positive by hemmaglutination, 3 (11.5 per cent) positive by skin test, and 1 (3.7 per cent) positive by immunofluorescence. At the end of the analysis, it was shown that 129 (35 per cent) individuals yielded at least two positive assays and, therefore, they should be considered as T. cruzi-infected individuals.