Resumen

ALARCON, Maritza et al. Presence of Trypanosoma cruzi in tissues of experimentally infected Wistar rats and their fetuses. Bol Mal Salud Amb [online]. 2006, vol.46, n.2, pp.137-148. ISSN 1690-4648.

This study was carried out with a group of 20 days old, 250-g female juvenile rats (Rattus norvegicus) of the Wistar strain. Each rat was inoculated, injecting it intraperitoneally with a 0.1- mL suspension of Blood with 1 x 105 tripomastigotes from the I/PAS/00/PLANALTO strain. The parasites were isolated from naturally infected Panstrongylus geniculatus from a street in an urban area in Caracas, Venezuela, and maintained in NMRI rats. At 10 days post-infection (pi), the rats were determined to have completed the estrual cycle and were then mated with males, with a ratio of 2 females and 1 male in each cage. Groups of virgin rats inoculated with T. cruzi (GII), healthy rats (GIII) and pregnant rats (GIV) were used as controls. Infection by T. cruzi in the GI rats revealed the highest levels of clear parasitemia with 12.2 ± 1.1 tripomastigotes/mm3 of blood at 18, 24 and 34 days (pi) with 6, 12 and 20 days from gestation, respectively, compared with GII. The titles of specific antibodies anti-T. cruzi were greater in the group of pregnant and infected rats in comparison with the infected unmated rats, represented by 1:512 and 1:2048 at 19 and 20 days (pi) respectively. 33% of the samples of amniotic fluid of the rats of GI developed flagellate forms of T. cruzi in NNN culture. Histopathological study of 6μm sections stained with hematoxilin-eosin of fetal hearts obtained from 2 rat fetuses revealed nests of amastigotes in the cardiac tissue. In the placentas of GI with 34 days of infection, we observed a placentitis characterized by intense inflammatory infiltration of the mononuclear and polymorphonuclear cells with neutrophyls predominant. The immunohistochemical assays using double marking with fluorescein isothiocyanatepropidium iodide and peroxidase-antiperoxidase in the sections of placenta, fetal hearths and umbilical cords showed parasites and abundant antigen of T. cruzi. These results demonstrate the fetal intrauterine infection by T. cruzi, confirming the transplacental transmission of the parasite from the infected mother to her offspring. Possibly the mechanism of congenital transmission is related to the release of the tripomastigotes across the trophoblast, to the taking up of the amniotic liquid by the fetuses or by the active penetration of the parasite across the skin and/ or mucosa during the fetal period.

Palabras clave : Trypanosoma cruzi; Wistar rats; tejidos fetales; transplacental transmission.