Comparison of Trypanosoma cruzi detection by PCR in blood and dejections of Triatoma infestans fed on patients with chronic Chagas disease.

In this study, we compare the sensitivity of detecting Trypanosoma cruzi in dejections of Triatoma infestans nymphs that had fed on the blood of chronic chagasic patients, with detection of T. cruzi in peripheral blood, using a polymerase chain reaction assay (PCR-D and PCR-B, respectively). Fifty-seven chronic patients were evaluated who were positive (group I) or negative (group II) by xenodiagnosis (XD). Patients showed 84.8 and 75% positive PCR results in both kinds of samples in groups I and II, respectively. Six cases (10.5%) showed positive PCR-D and negative PCR-B, five of them belonged to group I. In contrast, five cases of group II showed negative PCR-D and positive PCR-B. Overall, the PCR-D assay gave positive results in 52 out of 57 samples (91.2%), while 51 out of 57 (89.5%) were positive by PCR-B. In comparison, only 57.9% were positive by XD (p = 0.0001). In conclusion, PCR performed in dejection or blood was more sensitive for the parasite detection than xenodiagnosis. All patients (100%) were detected positive when both, PCR-D and PCR-B, were applied.