High infection rates ofTriatoma dimidiataare associated with low levels ofTrypanosoma cruziseroprevalence in Pedro Carbo, Ecuador. Use of atc24 gene-based PCR approach

In control programs for vectorial transmission of Chagas' disease, conventional microscopic procedures are generally performed to determine baseline levels of infectivity of vectors. Reported here are data using Polymerase Chain Reaction in the detection of Trypanosoma cruzi in Triatoma dimidiata, one of the principal vectors of Chagas' disease in Ecuador. The microscopy and PCR techniques showed a high percentage of vector infection in Pedro Carbo, province of Guayas (Ecuador), with 44.16% and 46.13% positive insects, respectively. This contrasted with the very low Chagas seropositivity recorded (0.5%). Since T. dimidiata was the only vector of the Chagas' disease found in Pedro Carbo and looking at the vector behavior, our data suggest that despite the high T. dimidiata infection, the low Chagas seropositivity detected is closely associated with the epidemiological and ecological context of T. dimidiata in Pedro Carbo.

A molecular phylogeographic study based on DNA sequences from individual metacercariae of Paragonimus mexicanus from Guatemala and Ecuador

A molecular phylogeographic study of Paragonimus mexicanus collected from Guatemala and Ecuador was performed. Genomic DNA was extracted from individual metacercariae, and two gene regions (partial mitochondrial cytochrome c oxidase subunit 1 (CO1) and the second internal transcribed spacer of the nuclear ribosomal gene repeat (ITS2)) were amplified by the polymerase chain reaction (PCR). Sequences segregated in a phylogenetic tree according to their geographic origins. ITS2 sequences from Ecuador and Guatemala differed at only one site. Pairwise distances among CO1 sequences within a country were always lower than between countries. Nevertheless, genetic distances between countries were less than between geographical forms of P. westermani that have been suggested to be distinct species. This result suggests that populations from Guatemala and Ecuador are genetically differentiated perhaps at the level of subspecies.

Trypanosoma cruzi isoenzyme variability in Ecuador: first observation of zymodeme III genotypes in chronic chagasic patients

We have analysed by multilocus enzyme electrophoresis (MLEE) at 21 genetic loci 10 Trypanosoma cruzi stocks isolated from chronic chagasic patients and 3 stocks isolated from Triatoma dimidiata collected in human habitats from the coastal part of Ecuador (all stocks isolated in August-December 1998). Isoenzyme profiles were compared to those of 4 laboratory-cloned stocks representing the major phylogenetic subdivisions of T. cruzi. This parasite's genetic variability in Ecuador proved to be considerable, even in this limited sample, since all main isoenzyme genotypes were recorded. Four stocks from patients were identical at all loci to the reference stock MNcl2 ('major clonet #39'; T. cruzi II) isolated in Chile. The 3 stocks isolated from T. dimidiata were closely related to the formerly described zymodeme I (T. cruzi I). Finally, 3 stocks from chronic chagasic patients (one with an asymptomatic form, 2 with a cardiac-digestive form) were closely related to the formerly described zymodeme III (presently not classified in either T. cruzi I or T. cruzi II). This is the first observation of this category of T. cruzi genotypes in chronic chagasic patients. In the past it was recorded only in acute patients, wild mammals and wild triatomine bugs. The epidemiological implications of these results are discussed.

An outbreak of fulminant hepatitis delta in the Waorani, an indigenous people of the Amazon basin of Ecuador

An outbreak of delta hepatitis occurred during 1998 among the Waorani of the Amazon basin of Ecuador. Among 58 people identified with jaundice, 79% lived in four of 22 Waorani communities. Serum hepatitis B surface antigen (HBsAg) was found in the sera of 54% of the jaundiced persons, and 14% of asymptomatic persons. Ninety-five percent of 105 asymptomatic Waorani had hepatitis B core (HBc) IgG antibody, versus 98% of 51 with jaundice. These data confirm that hepatitis B virus (HBV) infection is highly endemic among the Waorani. Sixteen of 23 (70%) HBsAg carriers identified at the onset of the epidemic had serologic markers for hepatitis D virus (HDV) infection. All 16 were jaundiced, where as only two of seven (29%) with negative HDV serology were jaundiced (P = .0006). The delta cases clustered in families, 69% were children and most involved superinfection of people chronically infected with HBV. The data suggest that HDV spread rapidly by a horizontal mode of transmission other than by the sexual route.

A molecular perspective on the genera Paragonimus Braun, Euparagonimus Chen and Pagumogonimus Chen

The status of the genera Euparagonimus Chen, 1963 and Pagumogonimus Chen, 1963 relative to Paragonimus Braun, 1899 was investigated using DNA sequences from the mitochondrial cytochrome c oxidase subunit I (CO1) gene (partial) and the nuclear ribosomal DNA second internal transcribed spacer (ITS2). In the phylogenetic trees constructed, the genus Pagumogonimus is clearly not monophyletic and therefore not a natural taxon. Indeed, the type species of Pagumogonimus, P. skrjabini from China, is very closely related to Paragonimus miyazakii from Japan. The status of Euparagonimus is less obvious. Euparagonimus cenocopiosus lies distant from other lungflukes included in the analysis. It can be placed as sister to Paragonimus in some analyses and falls within the genus in others. A recently published morphological study placed E. cenocopiosus within the genus Paragonimus and probably this is where it should remain.

Apolipoprotein B signal peptide polymorphism distribution among south Amerindian populations

We report the distribution of the APOB signal peptide polymorphism in 5 native populations of South America: 2 samples of Mataco and 1 sample each of Pilagá and Toba from the Argentinian Chaco and 1 sample of Ache from the Paraguay forest. A randomly selected subsample of a previously studied sample from the Cayapa of Ecuador (Scacchi et al. 1997) was reanalyzed to investigate probable differences attributable to sampling, laboratory techniques, or interobserver error. The polymorphism observed in the signal peptide region of the APOB gene among native populations of South America exhibits the same range of variation found among geographic continental populations, confirming the high genetic heterogeneity of South Amerindians. Extremes in the allele prevalences were found among the Mataco and Ache, populations not far apart geographically. The small differences in genotype and allele frequencies between the subsample of the Cayapa analyzed here and the original Cayapa sample and between the 2 Mataco samples were not statistically significant and most likely were due to sampling error.

Severe digestive pathology associated with chronic Chagas' disease in Ecuador: report of two cases

DNA extracted from peripheral blood of two Ecuadorian patients showing severe digestive pathology was amplified by the polymerase chain reaction using a Trypanosoma cruzi specific oligonucleotide primers derived from the primary sequence of a cDNA encoding for a 24 kDa excretory/secretory protein. The positive PCR results together with the clinical findings confirmed that both patients had a digestive pathology due to Chagas' disease. This pathology could be more frequent than previously described in the chagasic endemic regions of Andean countries.