A, Gross pathology in a 3-year-old Macaca fascicularis that died of naturally acquired Chagas disease, illustrating pulmonary edema, hydrothorax, hydropericardium, hepatomegaly, and rounded heart (arrow). Ascites have been drained. B, Histopathologic appearance of cardiac tissue in an infected M. fascicularis, illustrating the presence of focal to diffuse, primarily lymphocytic, myocardial infiltrates. H&E stain; bar = 200 μm. C, High power magnification of Panel B showing the presence within the cardiac muscle of a nest of organisms morphologically consistent with the amastigote form of T. cruzi (arrows). H&E stain; bar = 50 μm.