The influence of different Trypanosoma cruzi
biodemes on the evolution of the infection and on the histopathological lesions of the heart and skeletal muscles, during the experimental infection of Calomys callosus
, was investigated. Three groups of C. callosus
were infected, respectively, with parasite strains representative of three different Biodemes: Type I (Y strain), Type II (21 SF strain), and Type III (Colombian strain). For each group, normal C. callosus
were also used as controls. Marked differences have been detected in the responses of C. callosus
to the infection with the three strains in this model. The strains Types I and II (Y and 21 SF) determined moderate lesions, mostly in the myocardium, with low parasitism, a rapid course, and total regression of the lesions by the 60th day of infection. Differently, Type III strain (Colombian), was more pathogenic for C. callosus
and induced necrotic-inflam-matory lesions in skeletal muscles and myocardium, in correspondence to intracellular parasitism. Proliferation of fibroblasts and amorphous matrix deposits, followed by interstitial fibrosis were present. Progressive regression of the inflammatory changes and collagen deposits occurred spontaneously. The progression and regression of both inflammation and fibrosis induced by the Colombian strain were further submitted to quantitative evaluation by morphometry. Results of the morphometric studies presented good correlation with the histopathological findings. The results confirm the importance of the different biodemes in the determination of tissue lesions and the peculiarities of response of C. callosus
to infection with T. cruzi.