|Budget Amount *help
¥3,200,000 (Direct Cost : ¥3,200,000)
Fiscal Year 1998 : ¥700,000 (Direct Cost : ¥700,000)
Fiscal Year 1997 : ¥2,500,000 (Direct Cost : ¥2,500,000)
Chagas disease has two clinical manifestations, and the geographic distribution of which varies in the following : cardiac form in Central America, and both cardiac and intestinal ones in South America. Therefore, it is important to identify the genetic structure of T cruzi from both Americas in order to elucidate the pathogenicity of Chagas disease. Although many phylo- genetic studies of T.cruzi have been reported in South America, those in Central America have been few. Authors performed isozyme analysis for genetic characterization of T cruzi in Guatemala, Central America, and made a phylogenetic comparison with South American ones (Higo et al., 1997).
In this study we examined phylogenetically 100 isolates of T.cruzi from Guatemala, Mexico, Peru, Colombia, Ecuador, Brazil, Paraguay and Chile. Dendrogram drawn up by isozyme analysis of the isolates showed the presence of three main lineages which correspond to that reported by Higo et al. (1997). A unique South American strain, one
of the three lineages, was not distributed in Guatemala and Mexico, Central and North America. This geographic distribution of genetic forms seem to be related to that of the clinical forms. This evidence may suggest the genetic relation of T.cruzi to the pathogenicity of Chagas disease. Further studies are necessary to analyze the isolates from patients of each clinical type in each region.
Genetic exchange of T.cruzi in its reproduction is important to understand Chagas disease epidemiologically and pathologically. Among many bilological and genetic studies of this field, clonal multiplication has been suggested as the main reproduction by population genetic studies. However, recently a possibility of genetic exchange was reported. To assess the degree of genetic exchange, we examined 3 population genetic indices : (1) genotype distribution, (2) average heterozygosity, (3) linkage disequilibrium. Consequently we assumed that the genetic exchange would be occurring more frequently than expected so far. Further studies are needed based on different population genetic analyses. Less