Hybridization of blood samples from infants in Paraguay by using Trypanosoma cruzi II clone 39 strain and mini-exon gene as probe. Use of a hybridization method with blood sample PCR products has resulted in improvement of the sensitivity of the assay. Lanes 1, 8, and 9, infant blood samples (with a weak 300-basepair product on 2% agarose gel electrophoresis); lane 5, infant blood sample with a conspicuous PCR product used as a positive control; lanes 2, 3, 4, 6 and 7, infant blood samples that did not show PCR products on by agarose gel electrophoresis but were visualized by hybridization in lanes 2, 6, and 7; lane 10, PCR-negative control; lanes 11 and 12, positive controls, T. cruzi I (X10 cl1, clone 20) and T. cruzi II, (MN cl2, clone 39) respectively. WP = weak positive.