Epidemiology, biochemistry and evolution of Trypanosoma cruzi lineages based on ribosomal RNA sequences

Infected dogs as a risk factor in the transmission of human Trypanosoma cruzi infection in western Venezuela

“…However, what may not be ignored is the observed difference in behavior among the molecular typed Venezuelan isolates and those typed in other Latin-American countries. The fact that we have found in Venezuela the same T. cruzi lineages circulating in dogs and human in the same endemic area, do not support previous statements from other workers referring preferential association of T. cruzi genotypes with sylvatic (T. cruzi I) or domestic (T. cruzi II) cycles of transmission (Zingales et al, 1998(Zingales et al, , 1999. These results obtained in dogs, in conjunction with the predominance of T. cruzi lineage I in a large number of acute chagasic patients (Añez et al, 2004b) and those from triatominebugs and wild reservoirs (Añez et al, in preparation), lead us to conclude that T. cruzi I and T. cruzi II circulate in Venezuela irrespective of the geographical regions and/or endemic areas and that both of the lineages are responsible for the human clinical pictures of Chagas disease and for the relatively high prevalence of the American trypanosomiasis in dogs.…”

Haplotype distribution of five nuclear genes based on network genealogies and Bayesian inference indicates that Trypanosoma cruzi hybrid strains are polyphyletic

“…In spite of this great genetic diversity, the existence of two basic "types" of T. cruzi was suggested by the interpretation of typing schemes of 24S rRNA gene patterns (Souto et al, 1996) and isoenzymes (Tibayrenc, 1995), among others. After analysis of explicit phylogenetic evidence, based on Markov models of nucleotide substitution, and application of molecular clock dating estimates, the extent of the divergence between these two T. cruzi "types" was fully appreciated and revealed genetic distances comparable to distances between genera in other kinetoplastids (Briones et al, 1999;Zingales et al, 1999;Kawashita et al, 2001). The consideration of typing data in the light of explicit phylogenetic evidence supported the proposition of an expert committee that these two major T. cruzi "types", previously designated by a plethora of names, should be referred to as T. cruzi I and T. cruzi II groups (Anonymous, 1999).…”

Usefulness of microsatellite typing in population genetic studies of Trypanosoma cruzi

“…The division of T. cruzi into two major phylogenetic lineages has been officially recognized and they were named T. cruzi I and T. cruzi II (Momen 1999). The existence of the two groups is now well established on the basis of biological, epidemiological, biochemical and molecular data (revised in Zingales et al 1999). However, the significance of these divisions is still under debate (Brisse et al 1998.…”