The complexity of the sylvatic cycle of Trypanosoma cruzi in Rio de Janeiro state (Brazil) revealed by the non-transcribed spacer of the mini-exon gene

American trypanosamiasis occurs in nature as a sylvatic cycle, where Trypan osoma cruzi interacts with wild triatomines and mammalian reservoirs, such as marsupials, rodents, armadillos and other animals. Due tu difficulties i n trying to isolate T. cruzi stocks from the sylvatic cycle, very few studi es hal-e been performed in order to understand the parasite infection in na tural environments. Traditionally T. cruzi has been considered to be compos ed of a highly heterogeneous population of parasites. In contrast, the mini -exon and the 24S alpha rRNA gene loci have shown that T. cruzi stocks can be clustered in 2 major phylogenetic groups: lineage 1 and lineage 2. In th is report, 68 recently isolated T. cruzi samples from the sylvatic cycle be longing to different geographical areas in Rio de Janeiro, Brazil, have bee n typed based on a variable spot in the nun-transcribed spacer of the mini- exon gene. Eight isolates were from triatomines, 26 stocks were from golden -lion tamarins, 31 from opossums, 2 from rodents and 1 from a three-toed sl oth. Thirty (44 % - 30/68) isolates were typed as lineage 1, while 36 (53 % - 36/68) isolates were typed as lineage 2. Tno opossums presented mixed in fection. Therefore, 3 % (2/68) of the isolates were typed as lineage 1 + li neage 2. Using these geographical regions as models of sylvatic environment s, it was observed that 96 % of the Didelphis marsupialis were infected by lineage 2 isolates, while all 26 golden-lion tamarins were infected by line age 1. The results show preferential association of thr 2 lineages of T. cr uzi with different hosts, composing the complexity of the sylvatic cycle.