Molecular characterization of Trypanosoma cruzi and infection rate of the vector Triatoma dimidiata in Costa Rica.

According to the genetic characterization by the analysis of the miniexon gene, strains of Trypanosoma cruzi can be classified into six discrete typing units (DTUs), and the DTU 1 into four distinct genotypes associated with different life cycles. While Chagas disease is endemic in Costa Rica, T. cruzi isolates from this region have never been genetically characterized. An analysis of 16 isolates from Costa Rica, based on miniexon gene analysis, showed the existence of two different haplotypes in the country, closely related to the Colombian haplotype group TcIa and to sequences from several Mexican isolates, with eight variable positions in the alignment and a variability of 2.6% between the compared sequences. No relationship between the habitat, vector or host, and the haplotypes was found, suggesting an active flow of T. cruzi in the country. The present study also reports a very high infection rate (47.3%, 26 out of 55 specimens) in a Costa Rican population of Triatoma dimidiata, the main vector of Chagas disease in this country. The distribution and abundance of the parasite and its main vector suggest a high risk of Chagas disease emergence in Costa Rica.

Molecular evidence of intraspecific variability in different habitat-related populations of Triatoma dimidiata (Hemiptera: Reduviidae) from Costa Rica.

Intraspecific genetic variation among Triatoma dimidiata (Hemiptera: Reduviidae) from seven Costa Rican populations and from different domestic, peridomestic, and sylvatic ecotopes were analyzed. The complete nucleotide sequence of the nuclear ribosomal DNA internal transcribed spacer (ITS-2) and partial sequences of the cytochrome B (Cyt b) gene and the large ribosomal subunit RNA (16S) of mitochondrial DNA (mtDNA) were analyzed and compared. All ITS-2 sequences analyzed were identical and correspond to the haplotype T.dim-H1, the most common haplotype in Central American populations. Sequences of mtDNA revealed a 10.17% of polymorphism in Cyt b and 2.39% in 16S, suggesting that the Cyt b fragment is a useful marker to describe the genetic structure of populations, even at habitat-related level. The analyses of the 18 new combined T. dimidiata haplotypes (Cytb/16S/ITS-2) showed that the two main geographical locations and populations studied are genetically structured showing different haplotype profiling. Only one combined haplotype was shared in the studied areas (Cytb.d/16S.a). Seven haplotypes exclusive for domestic/peridomestic populations, five for sylvatic, and six shared haplotypes for both habitat-related ecotopes are described. Although the relationship between the habitat and the haplotype profiling is less clear, there are different patterns of haplotype distribution in each geographic area between the two habitat-related ecotopes studied (domestic/peridomestic and sylvatic), some of them reflected in the phylogenetic relationships analyzed. The intraspecific variability detected may underlie the known plasticity of T. dimidiata, an important vector for Chagas disease transmission, suggesting that this species must be continuously monitored.

Trypanosoma rangeli genotypes association with Rhodnius prolixus and R. pallescens allopatric distribution in Central America.

Previous kDNA polymorphism-based reports have revealed the existence of two Trypanosoma rangeli genotypes (KP1+ and KP1-): SL and SSU rRNA gene polymorphism-based studies have revealed that five genotypes (A-E) are distributed throughout different Latin-American countries. Some evidence has shown that the genotypes' biogeographical distribution is associated with sympatric Rhodnius species. 12 T. rangeli isolates from humans and reservoirs from El Salvador, Guatemala, Honduras, Costa Rica and Panama were characterised by kDNA and mini-exon gene intergene spacer analysis and compared to 12 previously characterised isolates from humans and vectors from Colombia, Guatemala, Honduras and Venezuela. Central American isolates corresponded to genotypes called KP1(+) or lineage A and KP1(-) or lineage C. Such dimorphism was corroborated by randomly amplified polymorphic DNA (RAPD) in 22 selected isolates; a dendrogram was thus produced having two defined branches. One branch grouped KP1(-) or lineage C strains isolated from Rhodnius colombiensis (Colombia), humans (Panama), Procyon lotor and Choloepus hoffmanni (Costa Rica). The other group was formed by KP1(+) or lineage A strains isolated from Rhodnius prolixus (Colombia, Venezuela) and humans (El Salvador, Guatemala, Honduras). These results present evidence that both groups infect different mammals (humans, domestic and silvatic animals) having no association with any particular vertebrate species; however, T. rangeli KP1(+) or (A) strains have been isolated in Central America in areas where R. prolixus circulate (Honduras, El Salvador and Guatemala) and KP1(-) or (C) strains have been isolated in areas where Rhodnius pallescens is the main vector (Panama and Costa Rica) indicating a parasite-vector association. The same lineages circulate in Andean countries (Colombia, Venezuela, Ecuador and Peru), KP1+ being associated with members of the prolixus group (R. prolixus and Rhodnius robustus) and KP1- with members of the pallescens group (R. pallescens, R. colombiensis and Rhodnius ecuadoriensis).