[en] Human Chagas disease is considered the most significant parasitic disease in Latin America. It is estimated that 16-18 million people are infected by T. cruzi. As a consequence, approximately 50,000 deaths occur every year. The acute infection usually goes unrecognized and enters into a chronic stage that persists throughout the host's life span. However, roughly 30% of infected individuals eventually will develop disease with an array of possible manifestations affecting the heart, the digestive tract, and/or the peripheral nervous system. This disease is commonly modeled in inbred mice even though mouse strains used to simulate experimental infection vary considerably. In this way, Wrightsman and Trischmann showed that chromosome 17 was directly involved in a T. cruzi resistance, showing the influence of host's genetic constitution on disease severity. Additionally, in 2003, Passos and Graefe, working separately, quantified parasite burdens in resistant and susceptible strains and applied a backcross strategy to map the genomic loci linked to susceptibility and resistance in inbred mice. The genomes of the animals were scanned with microsatellite markers and the results found by these authors showed that the resistance mechanism is polygenic and is under the control of a complex network. In the particular case of Y strain, in vivo assays indicated that survival was related to the chromosomes 7,11,14,17 and 19. In order to evaluate the influence of each isolated chromosome as well as their interactions, we employed susceptible isogenic mice to construct consomic lineages for each one of those chromosomes. The consomic strains were injected with irradiated and native forms of Y strain T. cruzi, and the infectivity parameters were evaluated by quantitative methods. Radiation caused inability of trypanosomes to infect and kill mice, when these parasites were irradiated with 1 kGy of gamma rays from a ⁶⁰Co source. In this experiment we used 10¹, 10², 10³, 10⁴ and 10⁵ parasites forms injected intraperitoneally, to understand the role of each of the chromosomes above on the resistance mechanisms. None of the consomic strain for the chromosomes 11, 14 and 17 survived to infection with non-irradiated parasites. However, the consomic strain for the chromosome 19; revealed that 38% of the animals survived after the injection with 10¹ forms in contrast with 10% after the injection with 10² forms. On the other hand, concerning the chromosome 7, 60% of the animals survived when 10¹ forms were injected, while 18% were able to control the infection with 10² forms. All consomic strains survived with the irradiated forms. These data could contribute with the understanding of the resistance mechanism in the Chagas disease, and suggest the importance of new experiments related with the immune response in these strains. (author)