The Ecotopes and Evolution of Trypanosoma cruzi and Triatomine Bugs
Trypanosoma cruzi infection is a zoonosis with a complex and poorly understood epidemiology. The species T. cruzi is genetically diverse. Two principal subspecific groups have been identified and named T. cruzi I and T. cruzi II, the latter with five subgroups (a-e). T. cruzi I predominates in the Amazon basin and in endemic countries north of the Amazon; T. cruzi II is the predominant cause of Chagas disease throughout the Southern Cone countries of South America. We have generated T. cruzi I hybrids in the laboratory from clonal parental genotypes. Phylogenetic analysis based on DNA sequence data indicates that genetic exchange has contributed significantly to the evolution of T. cruzi. Genetic exchange may facilitate the spread of virulence and drug resistance, or the extension of host range. We propose that T. cruzi I may have evolved in the palm tree ecotope associated with Didelphis hosts and Rhodnius vectors, and that T. cruzi II may have evolved in the terrestrial ecotope with edentate hosts and Triatoma vectors. Comparative genomics of diverse T. cruzi strains may give insight into the differential pathogenesis of severe and benign Chagas disease. Molecular taxonomy and population genetics research on both T. cruzi and its triatomine vectors can define where domestic and sylvatic transmission cycles overlap, and contribute to the design of disease control strategies. Priorities for control of Chagas disease are improved vector control, screening of blood and organ donors, and the development of new drugs to eliminate the present burden of human infection.
KeywordsSugar Shipping Cane Bark Argentina
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