Genetic structure of Trypanosoma cruzi populations from Argentina estimated from enzyme polymorphism

Abstract

Isolates of Trypanosoma cruzi from human patients, domestic and sylvatic animals and vector insects were obtained in different areas of Argentina. Electrophoretic patterns of enzymes from extracts of 95 isolates were analysed. On the basis of zymograms providing information on 10 loci, 12 zymodemes are described according to their genotypes. Data presented show fixed heterozygosity, absence of segregation of genotypes, significant departures from Hardy-Weinberg equilibrium, and over-represented genotypes. This evidence supports the hypothesis that sexual reproduction is very restricted or absent in this parasite. The proportion of polymorphic loci is 80%. The expected mean heterozygosity per locus (He) is 0.43, while the observed value (Ho) is 0.24. Differences between these values may be explained by accepting a basically clonal structure for T. cruzi. The data matrix of 12 zymodemes using 28 characters was analysed using a Wagner parsimony algorithm. Two equally most parsimonious unrooted trees were generated; both have 39 steps. The results show clusters clearly separated according to the geographical origin of the stocks. There are some indications of some correlations between genetic composition of the parasite and the clinical picture of the infection in human patients.

Molecular epidemiology of domestic and sylvatic Trypanosoma cruzi infection in rural northwestern Argentina

“…In the late 1980s, when intense domestic transmission of T. cruzi was prevalent and widespread, sylvatic mammals (opossums, ferrets and skunks) were sometimes found infected with TC IId, which also infected domestic dogs and Tr. infestans in Santiago del Estero (Wisnivesky-Colli et al, 1992;De Luca d'Oro et al, 1993). In such an epidemiological context of intense transmission, the observed distribution of lineages was probably a spillover of parasite strains from domestic into sylvatic habitats.…”

“…Previous studies based on MLEE concluded that domestic and sylvatic transmission cycles of T. cruzi overlapped partially throughout Argentina including rural areas within the Chaco region (Wisnivesky-Colli et al, 1992;De Luca d'Oro et al, 1993;Diosque et al, 2003). In the late 1980s, when intense domestic transmission of T. cruzi was prevalent and widespread, sylvatic mammals (opossums, ferrets and skunks) were sometimes found infected with TC IId, which also infected domestic dogs and Tr.…”

“…To assess the occurrence of variation in the distribution of T. cruzi lineages among hosts within the same region we compared our results (2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007) with data collected in Santiago del Estero Province in the late 1980s (De Luca D'Oro et al 1993) and in Chaco Province over 1999(Diosque et al 2003 (Table 3). Given the low numbers of humans and opossums sampled and the homogeneity of results, for these host species we pooled our data with the Chaco data and compared these with data published by De Luca D 'Oro et al (1993).…”

“…In Argentina, very few studies have attempted to type the local T. cruzi strains, and parasites have been characterized mainly by multilocus enzyme electrophoresis (MLEE) (Montamat et al, 1987;De Luca d'Oro et al, 1993;Diosque et al, 2003). Parasite zymodemes reported by De Luca d 'Oro et al (1993) were later analyzed by Barnabé et al (2000) and reinterpreted as belonging to TC I, TC IIb and TC IId.…”

“…Parasite zymodemes reported by De Luca d 'Oro et al (1993) were later analyzed by Barnabé et al (2000) and reinterpreted as belonging to TC I, TC IIb and TC IId. Overall, T. cruzi II (TC II) was more prevalent in the domestic environment, and sylvatic mammals were found infected with both TC I and TC II (De Luca d'Oro et al, 1993). TC IIe was first reported in Argentina by Diosque et al (2003) and TC IIc by Ceballos et al (2006).…”