Macrophage activation and histopathological findings in Calomys callosus and Swiss mice infected with several strains of Trypanosoma cruzi.

Peritoneal macrophage activation as measured by H2O2 release and histopathology was compared between Swiss mice and Calomys callosus, a wild rodent, reservoir of Trypanosoma cruzi, during the course of infection with four strains of this parasite. In mice F and Y strain infections result in high parasitemia and mortality while with silvatic strains Costalimai and M226 parasitemia is sub-patent, with very low mortality. H2O2 release peaked at 33.6 and 59 nM/2 x 10(6) cells for strains Y and F, respectively, 48 and 50 nM/2 x 10(6) for strains Costalimai and M226, at different days after infection. Histopathological findings of myositis, myocarditis, necrotizing arteritis and absence of macrophage parasitism were found for strains F and Costalimai. Y strain infection presented moderate myocarditis and myositis, with parasites multiplying within macrophages. In C. callosus all four strains resulted in patent parasitemia which was eventually overcome, with scarce mortality. H2O2 release for strains Y and F was comparable to that of mice-peaks of 27 and 53 nM/2 x 10(6) cells, with lower values for strains Costalimai and M226-16.5 and 4.6 nM/2 x 10(6) cells, respectively. Histopathological lesions with Y and F strain injected animals were comparable to those of mice at the onset of infections; they subsided completely at the later stages with Y strain and partially with F strain infected C. callosus. In Costalimai infected C. callosus practically no histopathological alterations were observed.