RESUMO
To determine the role of Trypanosoma cruzi superinfections on the outcome of Chagas' disease, groups of BALB/c mice were prime-infected with low virulence clones h1 and h2 and challenged with high virulence clones m3 and m4. All mice injected with the m3 and m4 clones succumbed before or at 16 days postinfection. In contrast, all mice injected with the h1 and h2 clones survived the prime infection and were superinfected with the m3 and m4 clones. Low-level parasitemias were observed in mice after challenge with the virulent clones. The mortality ratios in the superinfected mice were not statistically different from those seen in the mice that received a single T. cruzi injection. The histopathological lesions recorded during the course of the infections showed features in the superinfected mice similar to those seen in the animals receiving a single infection. These data argue that morbidity and mortality in BALB/c mice, infected with T. cruzi clonal lines, are not associated with the frequency of receiving the parasite burden.