Parasitology



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


O. FERNANDES a1a6c1, R. H. MANGIA a2, C. V. LISBOA a3, A. P. PINHO a3, C. M. MOREL a2, B. ZINGALES a4, D. A. CAMPBELL a5 and A. M. JANSEN a2
a1 Department of Tropical Medicine, Instituto Oswaldo Cruz, Fiocruz, Rio de Janeiro, Brazil
a2 Department of Biochemistry and Molecular Biology, Instituto Oswaldo Cruz, Fiocruz, Rio de Janeiro, Brazil
a3 Department of Protozoology, Instituto Oswaldo Cruz, Fiocruz, Rio de Janeiro, Brazil
a4 Department of Biochemistry, Instituto de Quimica, Universidade de São Paulo, São Paulo, Brazil
a5 Department of Microbiology and Immunology, UCLA School of Medicine, Los Angeles, USA
a6 Department of Pathology, UERJ, Rio de Janeiro, Brazil

Abstract

American trypanosamiasis occurs in nature as a sylvatic cycle, where Trypanosoma cruzi interacts with wild triatomines and mammalian reservoirs, such as marsupials, rodents, armadillos and other animals. Due to difficulties in trying to isolate T. cruzi stocks from the sylvatic cycle, very few studies have been performed in order to understand the parasite infection in natural environments. Traditionally T. cruzi has been considered to be composed of a highly heterogeneous population of parasites. In contrast, the mini-exon and the 24Sα rRNA gene loci have shown that T. cruzi stocks can be clustered in 2 major phylogenetic groups: lineage 1 and lineage 2. In this report, 68 recently isolated T. cruzi samples from the sylvatic cycle belonging to different geographical areas in Rio de Janeiro, Brazil, have been typed based on a variable spot in the non-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 sloth. Thirty (44% – 30/68) isolates were typed as lineage 1, while 36 (53% – 36/68) isolates were typed as lineage 2. Two opossums presented mixed infection. Therefore, 3% (2/68) of the isolates were typed as lineage 1+lineage 2. Using these geographical regions as models of sylvatic environments, it was observed that 96% of the Didelphis marsupialis were infected by lineage 2 isolates, while all 26 golden-lion tamarins were infected by lineage 1. The results show preferential association of the 2 lineages of T. cruzi with different hosts, composing the complexity of the sylvatic cycle.

(Received May 21 1998)
(Revised August 11 1998)
(Accepted August 11 1998)


Key Words: Trypanosoma cruzi; mini-exon gene; sylvatic cycle; Didelphis marsupialis; Leontophitecus rosalia.

Correspondence:
c1 Corresponding author: Department of Tropical Medicine, Instituto Oswaldo Cruz, Fundação Oswaldo Cruz, Av. Brasil 4365, CEP 21045-900, RJ – Brazil. Tel/Fax: 005521 280 3740. E-mail: octaviof@gene.dbbm.fiocruz.br


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