A histopathological analysis of the course of myocarditis in C3H/He mice infected with Trypanosoma cruzi clone Sylvio-X10/4.

The histopathology of hearts of C3H/He (MTV-) mice infected for 2 to 440 days with Trypanosoma cruzi clone Sylvio-X10/4 was examined. Inflammation was present in most hearts at 14 days post-infection (d.p.i.) and persisted thereafter. Myocardial fibrosis, which was first seen 45 d.p.i. and was more marked after 200 d.p.i., developed at a time when few parasites were present. Fibrosis predominated in subepicardial and subendocardial myocardium, areas of most severe inflammation. Parasites were restricted to myocardial fibres and were found in all mice infected for 14 to 30 days and, in fewer numbers, in 54% of mice infected for more than 30 days. T. cruzi-induced myocarditis in mice was not a self-resolving disease but a dynamic, active process occurring continuously over a long time following infection. This clone-derived T. cruzi stock produced a myocarditis in inbred mice similar to that seen in human chronic Chagas' disease.