The affinity of the lectins Ricinus communis and Glycine maxima to carbohydrates on the cell surface of various forms of Trypanosoma cruzi and Trypanosoma rangeli, and the application of these lectins for the identification of T. cruzi in the feces of Rhodnius prolixus.

Flagellates of Trypanosoma cruzi (stock Molino 1), obtained from the intestine of experimentally infected Rhodnius prolixus, grown in cellular or acellular culture, as well as from the blood of infected mice, were examined by a direct fluorescence test using the lectins RCA (Ricinus communis-120) and SBA (soy bean agglutinin; Glycine maxima), conjugated with fluorescein isothiocyanate, for the detection of beta-D-galactose and alpha,beta-N-acetyl-D-galactosamine on the membranes of the flagellates. The same reactions were carried out using Trypanosoma rangeli (stock San Agustin), obtained from the intestine, hemo-lymph or salivary glands of experimentally infected R. prolixus, as well as from cultures and from the blood of experimentally infected CFW mice. The results indicate that the membrane of T. rangeli in the salivary glands of the vector contains beta-D-galactose, but that this sugar is absent from all other developmental stages of this trypanosome. All stages of intestinal and cultured. T. cruzi presented positive reactions with RCA-FITC and SBA-FITC. The high specificity of this technique makes it useful for the examination of R. prolixus, previously used in xenodiagnosis of Chagas' disease and for the examination of intradomiciliary or sylvatic vectors in epidemiological surveys in areas where T. cruzi and T. rangeli coexist. Formaldehyde fixed samples can be examined months later and false reports due to T. rangeli can be avoided.