A comparative pathological study of three strains of Trypanosoma cruzi in an experimental model

Trypanosoma cruzi, the etiological agent of Chagas' disease, shows a wide variation in its biological behaviour depending on the geographical distribution of different strains. Moreover, some strains can show variations with the course of time. We have studied the tissular tropism of three strains of T. cruzi, Cali, Bolivia and Y, from different geographical origins (Colombia, Bolivia and Brasil respectively) on Swiss mice in order to detect any possible modification in their behaviour attributable only to parasite but not to host variations. The anatomopathological study of sections from heart, brain, liver, spleen, lymphatic ganglion, skeletal muscle and colon from Swiss mice infected with these strains has evidenced the presence of some important discrepancies between the tissular tropism expected from their former descriptions, and classical typification and then observed lesions. The greatest variations were found in the Y strain which had been described as eminently reticulotropic but presented lesions in all the organs except the spleen and lymphatic ganglion. We consider that the variations found in our study can only be explained in terms of changes in the properties of the strains considered, and conclude that the classic typification techniques based on the constancy of the characteristics of the parasite are not fully reliable for the description and clinical management of some evolving strains.