Trypanosoma cruzi primary infection prevents severe re-infection in mice

the effect of trypanosoma cruzi re-inoculations on experimentally infected mice was evaluated. mice received a primary infection by intradermal inoculation of 5x103 t. cruzi metacyclic infective forms from laboratory infected rhodnius prolixus. from 200 mice initially infected, 52 survived the course of the infection during 23 weeks. from these, 45 mice were re-inoculated and seven used as infected control. two re-inoculations were performed using the same conditions as in the prime-infection. observations on re-inoculated mice revealed a parasitemia level lower than that detected during the primary-infection. serologic evaluation showed no variation in the immunoglobulin profile, maintaining similar igm and igg levels after re-inoculations. similar mortality rates were observed in primary-infected, re-inoculated and infected control mice. no remarkable histopathological changes attributable to re-inoculation were detected. these results lead us to conclude that t. cruzi re-inoculation in mice previously infected with the same parasite does not produce a reactivation of infection similar to the typical acute clinical or immunological profiles. this also suggests that t. cruzi primary infection may prevent severe re-infection, establishing a protective stage making infected mice resistant to a second infection. epidemiological implications of the present findings are discussed.