Histopathological and immunohistochemical study of the brain in the acute and chronic phases of experimental trypanosomiasis cruzi in dogs.

A histopathological and immunohistochemical study was undertaken of the brains of 12 young purebred Pinscher dogs, eight of which were inoculated intraperitoneally with the Colombiana strain of Trypanosoma cruzi. The four non-infected dogs formed the control group. An immunoperoxidase method was employed for demonstrating amastigotes of T. cruzi in tissue sections. Three infected dogs died in the acute phase; the other five were sacrificed at different stages of the chronic phase, one of them having survived for almost three years after the inoculation. Histopathological and immunohistochemical examination of the brains showed changes only in the infected group. Three of the eight inoculated dogs showed encephalitis in multiple foci. In one of the dogs the lesion was recent, in activity, containing parasites. In the other two dogs the lesions were milder, without parasites, suggesting a process of regression. These three were the dogs which died in the acute phase. The other five infected dogs did not show brain changes, and these were the dogs which were sacrificed at different stages of the chronic phase. Based on these findings, the authors conclude that, in the experimental model used, central nervous system involvement in the acute phase of the infection is not very frequent. In the chronic phase the inflammatory changes and parasites would not have been still observable, firstly because most of these dogs would not have had central nervous system involvement in the acute phase, and secondly because in some dogs there would have been total regression of any mild inflammatory changes which had been present in the acute phase as the infection progressed to the chronic phase.