[Effect of reinfection on the development of rats infected with Trypanosoma cruzi]

The present study was undertaken in order to demonstrate that reinfection could modify parasitemia, serum antibodies, electrocardiographic patterns and/or myocardial lesions already observed in a rat model. Experimental groups IG: rats infected at weaning with 1 x 10(6) T. cruzi; RG: same as IG plus reinoculations each 30 days until completion on day 150; IG1: 51 day old infected rats; C: controls. A high parasitemia was detected in IG and RG until day 20 showing a tendency to become negative on day 30. No parasites were observed in RG after the first reinoculation which could not be attributed to the old age of the host since there was no parasitemia in IG1. Xenodiagnosis were negative in all three groups. Serum antibodies were not significantly modified in RG in comparison with IG, except for 7S antibodies, since RG showed higher titres in some days under study. No distinct patterns of basal ECG were observed in infected rats. The ajmaline test reduced the heart rate (HR) showing no treatment dependence. The PR, QaT and QRS were significantly lengthened in all groups regarding the basal one (p less than 0.05), except for the QaT in C. Besides, the PR and QaT alterations were greater in the infected rats (p less than 0.05). There was also present a wide variety of electric axis orientations, regarding the basal value, accompanied by morphological changes more evident in the RG. The incidence of cardiac lesions histologically detected in the infected group was significantly higher than in C (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)