Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “SOUTH AMERICA”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 271 records · Page 15Linked to original sources
PubMed2006

Genetic diversity of Plasmodium vivax Pvcsp and Pvmsp1 in Guyana, South America.

Approximately 55% of malaria infections in the Guyana Amazon region are attributed to Plasmodium falciparum while the other 45% are attributed to non-falciparum, mostly Plasmodium vivax. However, little is known about the P. vivax strain types circulating in the region. Using PCR for Plasmodium detection and two genetic markers specific to P. vivax to detect the polymorphic circumsporozoite protein (CSP) and the conserved 19-kDa region of the merozoite surface protein-1 (MSP-1), we investigated the overall Plasmodium strain distribution and population diversity within P. vivax in isolates collected from the blood of infected individuals in the interior Amazon region of Guyana, South America. Out of a total of 250 samples positive for Plasmodium, P. vivax was detected in 30% (76/250) and P. falciparum was detected in 76% (189/250). Mixed infections containing both P. falciparum and P. vivax constituted 6% (15/250) of the total positive samples. Further analysis of P. vivax strains showed that 92% (56/61) of the P. vivax samples hybridized with a probe specific to type VK210, 39% (24/61) hybridized with a probe specific for type VK247, and 25% (15/61) hybridized with a probe specific for the P. vivax-like CS genotype. DNA sequencing of the 19-kDa C-terminal domain in block 13 of MSP-1 amplified from 61 samples from patients infected with P. vivax demonstrated that this region is highly conserved, and all samples were identical at the nucleotide level to the Belem and Salvador-1 types. No synonymous or nonsynonymous mutations were observed in this region of the gene, indicating that current vaccine-development efforts based on the MSP-1(19) fragment would be applicable in Guyana.

Animals↗
PubMed2003

Sampling strategies for delimiting species: genes, individuals, and populations in the Liolaemus elongatus-kriegi complex (Squamata: Liolaemidae) in Andean-Patagonian South America.

Recovery of evolutionary history and delimiting species boundaries in widely distributed, poorly known groups requires extensive geographic sampling, but sampling regimes are difficult to design a priori because evolutionary diversity is often "hidden" by inadequate taxonomy. Large data sets are needed, and these provide unique challenges for analysis when they span intra- and interspecific levels of divergence. However, protocols have been designed to combine methods of analysis for DNA sequences that exhibit both very shallow and relatively deeper divergences. In this study, we combined several tree-based phylogeny reconstruction methods with nested-clade analysis to extract maximum historical signal at various levels in the poorly known Liolaemus elongatus-kriegi lizard complex in temperate South America. We implemented a recently descrirbed tree-based protocol for DNA sequences to test for species boundaries, and we propose modifications to accommodate large data sets and gene regions with heterogeneous substitution rates. Combining haplotype trees with nested-clade analyses allowed testing of species boundaries on the basis of a priori defined criteria. The results obtained suggest that the number of putative species in the L. elongatus-kriegi complex could be doubled. We discuss these findings in the context of the advantages and limitations of a combined approach for retrieval of maximum historical information in large data sets and with reference to the yet formidable unresolved issues of sampling strategies.

Animals↗
PubMed1997

Comparative performances of enzyme-linked immunosorbent, western blot, and polymerase chain reaction assays for human T-lymphotropic virus type II infection that is endemic among Indians of the Gran Chaco region of South America.

BACKGROUND: Human T-cell lymphoma/leukemia viruses types I and II (HTLV-I and HTLV-II) are related exogenous human retroviruses. The former is definitely pathogenic while disease association with the latter is unclear. There are two subtypes of HTLV-II, A and B. Currently, enzyme-linked immunosorbent assays (ELISAs) based on HTLV-I antigens are used to screen for the presence of HTLV-I and -II antibodies. Confirmation and subtyping are accomplished by Western blot (WB) or ELISAs based on HTLV-I whole viral antigens and/or HTLV-I and HTLV-IIA peptides. The sensitivity and specificity of these serologic assays were compared to those of HTLV-I and-II-specific polymerase chain reaction (PCR) assays in tests on samples from Indians from South America in whom the HTLV-IIB subtype is endemic. STUDY DESIGN AND METHODS: Sera from 246 Gran Chaco Indians were evaluated for HTLV antibodies with the use of four ELISAs (Retrotek HTLV-I; Cambridge Biotech rgp21 enhanced HTLV-I/II; Vironostika HTLV-I/II; and Select HTLV-I/II), and a WB assay. Peripheral blood leukocyte DNA from each Indian was analyzed for HTLV-I or HTLV-II pol DNA via PCR. Fifteen of the PCR-positive samples were further subtyped via cloning and sequencing and/or oligomer restriction. RESULTS: Ninety-seven samples (39%) were positive for HTLV-II by serologic and/or PCR assays. All 15 positive DNA samples that were further analyzed were of the HTLV-IIB subtype and were clustered as a highly conserved phylogenetic group. Comparative analyses indicate that the sensitivity and specificity of the various assays were: PCR, 97 and 100 percent; Retrotek, 70 and 91 percent; Cambridge Biotech, 74 and 96 percent; Vironostika, 73 and 99 percent; Select 72 and 98 percent; and WB, 70 and 100 percent. CONCLUSION: The sensitivities of the tested HTLV serologic assays were comparable. However, the specificity of the Retrotek ELISA was significantly lower than that of the others. When positive, the subtyping assays were very specific. However, PCR assays would seem preferable or to be a necessary adjunct for the sensitive detection of HTLV-IIB infection.

Adolescent↗
PubMed2005

Direct genotyping of animal and human isolates of Toxoplasma gondii from Colombia (South America).

Genetic analysis of the SAG2 locus was performed to determine the prevalence of the main genotypes of Toxoplasma gondii (SAG2 types I, II, and III) associated with humans, cats, birds and guinea pig toxoplasmosis in Colombia. This typing was directly performed on clinical samples and autopsy material from human or animals. A total of 50 from 146 samples were positive by specific B1 Toxoplasma PCR assay and then were analyzed by restriction fragment length polymorphism in PCR-amplified SAG2 products. Characterization of the SAG2 gene was successful in 33 (66%) of the samples. Genotyping indicated that 31 (93.9%) were SAG2 type I, 1 was SAG2 type III and 1 was atypical. In birds and cats all samples were SAG2 type I. Results support a predominance of the Toxoplasma SAG2 type I circulating in human and animals in South America.

Animals↗
PubMed1989

Successful intercontinental transport of porcine embryos from Europe to South America.

A total of 393 porcine embryos was transported in two trials each lasting more than 30h from Hannover, Federal Republic of Germany to Buenos Aires, Argentina. The embryos were shipped in phosphate buffered saline (PBS) medium supplemented with 10% lamb serum and packaged in 0.25ml straws placed in a modified thermos bottle at 36.5 degrees C. Upon arrival, 359 embryos (90.8%) were evaluated as morphologically intact and were transferred to 19 recipients. Twelve recipients remained pregnant. Three recipients aborted and nine recipients (47.4%) farrowed a mean number of 5.6 +/- 2.6 (x +/- SD) piglets after 115.1 +/- 1.8 d of gestation. The average birthweight was 1.1 +/- 0.2 kg. The percentage of embryos resulting in live piglets was 28.6% in farrowing recipients. These births represented the first piglets from embryos that had been stored for more than 30h in vitro and shipped from Europe to South America.

Journal Article↗
PubMed2005

Biological and DNA evidence of two dissimilar populations of the Rhipicephalus sanguineus tick group (Acari: Ixodidae) in South America.

In this work, the biology, mitochondrial DNA and fertility of hybrids from two strains of Rhipicephalus sanguineus, from Brazil and Argentina, were compared. Engorged larvae, nymphs and adults from Argentina weighed more and the engorgement period of adult females was significantly longer than those of their Brazilian counterparts, whereas adult female tick yield rate was higher for the Brazilian strain. High intraspecific divergence of mitochondrial DNA was detected between R. sanguineus from Brazil and Argentina. On the other hand, a strong genetic relationship was detected between European and Argentinean R. sanguineus populations while the Brazilian population appeared to be related to the African Rhipicephalus turanicus. Adult hybrid females laid eggs, which were mostly unviable, whereas a mean of more than 1400 larvae hatched per egg mass from pure Brazilian and Argentinean strains. These results showed that differences between these strains are greater than previously assumed and that the biosystematic status of R. sanguineus ticks from South America should be re-evaluated. Wide variations, such as these might account for the reported worldwide differences in biology and vector capacity of this species.

Animals↗
PubMed2004

Atmospheric heavy metals in tropical South America during the past 22,000 years recorded in a high altitude ice core from Sajama, Bolivia.

V, Co, Cu, Zn, As, Rb, Sr, Ag, Cd, Ba, Pb, Bi and U have been analysed by inductively coupled plasma sector field mass spectrometry in various sections of a dated snow/ice core drilled at an altitude of 6542 m on the Sajama ice cap in Bolivia. The analysed sections were dated from the Last Glacial Stage ( approximately 22,000 years ago), the Mid-Holocene and the last centuries. The observed variations of crustal enrichment factors (EFc) for the various metals show contrasting situations. For V, Co, Rb, Sr and U, EFc values close to unity are observed for all sections, then showing that these elements are mainly derived from rock and soil dust. For the other metals, clear time trends are observed, with a pronounced increase of EFc values during the 19th and 20th centuries. This increase shows evidence of metal pollution associated with human activity in South America. For Pb an important contribution was from gasoline additives. For metals such as Cu, Zn, Ag and Cd an important contribution was from metal production activities, with a continuous increase of production during the 20th century in countries such as Peru, Chile and Bolivia.

Air Pollutants↗
PubMed2006

Serotyping of Toxoplasma gondii in chronically infected pregnant women: predominance of type II in Europe and types I and III in Colombia (South America).

Isolates of Toxoplasma gondii, which is responsible for a wide range of clinical manifestations are grouped into three clonal lineages of different virulence in mice. However, it is not clear whether this genotypic pattern is associated with the clinical profile of the disease in humans nor is the geographical distribution of the genotypes known. This is mainly due to difficulties in obtaining parasitic DNA from patients. The available data are therefore limited and originate from acute or congenital infections or from animals. A non-invasive assay is needed to address issues of strain type, geographical distribution and severity of clinical toxoplasmosis. To serotype T. gondii strains, we have developed an enzyme-linked immunosorbent assay (ELISA) that uses polymorphic polypeptides specific to the three clonal lineages and derived from two dense granule antigens, GRA5 and GRA6. Two hundred and fifty-two sera from chronically infected pregnant women from three different European countries and Colombia were investigated. The analysis of genotype-specific antibody response showed a homogeneous type II distribution in the European samples compared with types I and III but no type II in the Colombian population. Our data concord with those obtained from the genotyping of other isolates from Europe and South America. We demonstrated that, despite some limitation due to antigen and/or antibody specificity, serotyping is a promising assay to investigate the relationship between type of strain and severity of the disease.

Amino Acid Sequence↗
PubMed2006

Characterization of Toxoplasma gondii isolates in free-range chickens from Chile, South America.

The prevalence of Toxoplasma gondii in free-ranging chickens is a good indicator of the prevalence of T. gondii oocysts in the soil because chickens feed from the ground. The prevalence of T. gondii in 85 free-range chickens (Gallus domesticus) from Chile was determined. Antibodies to T. gondii were assayed by the modified agglutination test (MAT), and found in 47 of 85 (55.3.9%) chickens with titers of 1:5 in six, 1:10 in four, 1:20 in four 1: 40 in three, 1: 80 in nine, 1: 160 in four 1:320 in nine, and 1: 640 or higher in eight. Hearts and brains of 47 chickens with titers of 1:5 or higher were pooled for each chicken and bioassayed in mice. Tissues from 16 seronegative (MAT<1:5) chickens were pooled and fed to one T. gondii-free cat. Feces of the cat were examined for oocysts but none was found based on bioassay of fecal floats in mice. Hearts and brains from seven seronegative (<1:5) were pooled and bioassayed in mice; T. gondii was not isolated. T. gondii was isolated by bioassay in mice from 22 chickens with MAT titers of 1:20 or higher. Genotyping of these 22 isolates using polymorphisms at the loci SAG1, SAG2, SAG3, BTUB and GRA6 revealed three genotypes. Seventeen isolates had type II alleles and four isolates had type III alleles at all loci. One isolate contained the combination of type I and III alleles. This is the first report of genetic characterization of T. gondii isolates from Chile, South America.

Agglutination Tests↗
PubMed1999

Usefulness of spoligotyping in molecular epidemiology of Mycobacterium bovis-related infections in South America.

Two hundred twenty-four Mycobacterium bovis isolates, mainly from South American countries, were typed by spoligotyping, and 41 different spoligotypes were identified. A total of 202 M. bovis isolates (90%) were grouped into 19 different clusters. The largest cluster contained 96 isolates (42.8%) on the basis of the most frequently observed spoligotype, spoligotype 34. Nineteen M. bovis isolates from humans in Argentina had spoligotypes and polymorphic GC-rich repetitive sequence (PGRS) types that represented the most common types found among isolates from cattle. All five isolates from Uruguay and three of the six isolates from Paraguay had spoligotypes that were also detected for isolates from Argentina. The spoligotypes of isolates from Brazil, Costa Rica, and Mexico and of some of the isolates from Paraguay could not be found in Argentina. A total of 154 M. bovis isolates were selected in order to compare the discriminative power of spoligotyping and restriction fragment length polymorphism (RFLP) analysis with direct repeat (DR) and PGRS probes. By spoligotyping, 31 different types were found, while AluI-digested DR probe-associated RFLP analysis identified 42 types, and RFLP analysis with the PGRS probe also detected 42 types; these were partly independent of the DR types. By combining the results obtained by spoligotyping and by RFLP analysis with the DR and PGRS probes, 88 different types were obtained. Although the differentiation of M. bovis by spoligotyping was less discriminatory than differentiation by RFLP analysis with the DR and PGRS probes, spoligotyping is easier to perform and its results are easier to interpret. Therefore, for the purpose of typing of M. bovis isolates, spoligotyping could be performed first and the isolates could be grouped into clusters and then analyzed by RFLP analysis with the DR and PGRS probes.

Animals↗
PubMed2002

Possible migration routes into South America deduced from mitochondrial DNA studies in Colombian Amerindian populations.

Mitochondrial DNA haplotype studies have been useful in unraveling the origins of Native Americans. Such studies are based on restriction site and intergenic deletion/insertion polymorphisms, which define four main haplotype groups common to Asian and American populations. Several studies have characterized these lineages in North, Central, and South American Amerindian, as well as Na Dene and Aleutian populations. Siberian, Central Asian, and Southeast Asian populations have also been analyzed, in the hope of fully depicting the route(s) of migration between Asia and America. Colombia, a key route of migration between North and South America, has until now not been studied. To resolve the current lack of information about Colombian Amerindian populations, we have investigated the presence of the founder haplogroups in 25 different ethnic groups from all over the country. The present research is part of an interdisciplinary program, Expedición Humana, fostered by the Universidad Javeriana and Dr. J. E. Bernal V. The results show the presence of the four founder A-D Amerindian lineages, with varied distributions in the different populations, as well as the presence of other haplotypes in frequencies ranging from 3% to 26%. These include some unique or private polymorphisms, and also indicate the probable presence of other Asian and a few non-Amerindian lineages. A spatial structure is apparent for haplogroups A and D, and to a lesser extent for haplogroup C. While haplogroup A and D frequencies in Colombian populations from the northwestern side of the Andes resemble those seen in Central American Amerindians more than those seen in South American populations, their frequencies on the southeastern side more closely resemble the bulk of South American frequencies so far reported, raising the question as to whether they reflect more than one migration route into South America. High frequencies of the B lineage are also characteristic of some populations. Our observations may be explained by historical events during the pre-Columbian dispersion of the first settlers and, later, by disruptions caused by the European colonization.

Colombia↗
PubMed2006

Ecology and epidemiology of avian influenza in North and South America.

Wild waterfowl and shorebirds are known to be the natural reservoir for influenza A viruses. Surveillance studies in waterfowl and shorebirds in North America show that influenza A viruses are repeatedly recovered from these birds. However, the virus recovery is influenced by geography, season, age and species of birds. In addition to the natural reservoir, the live-bird marketing system (LBMS) in certain regions of the United States has been recognized as a man-made reservoir of influenza viruses and has been linked to several outbreaks of low pathogenicity avian influenza (LPAI) in poultry. Outbreaks of LPAI in commercial poultry is attributed to movement of infected birds, dirty or improperly cleaned crates, and contaminated vehicles from the LBMS to poultry farms. However, in the majority of outbreaks in poultry, the source of infection is suspected to be wild aquatic birds or the source is unknown. Since 2002, three outbreaks of highly pathogenic avian influenza (HPAI) have occurred in the Americas; one each in Chile (H7N3), United States (H5N2), and Canada (H7N3). In each of these outbreaks, a precursor virus of low pathogenicity mutated to become highly pathogenic after circulating in poultry. The HPAI viruses recovered from the three outbreaks had unique molecular and phenotypic characteristics that do not conform to other known HPAI viruses. These findings emphasize the need for monitoring wild and domestic bird species for presence of influenza A viruses.

Age Factors↗
PubMedDate not supplied

Control of the transmission of Vibrio cholerae and other enteropathogens by foods originating from endemic areas in South America and elsewhere as a model situation.

The cholera-pandemic raging in South and Middle America and endemic cholera in other countries call for measures of health protection of the local population, but particularly with respect to the young, old, pregnant and immunocompromised citizens of countries importing food from the areas where the disease has struck. Instead of harshly barring importation, a more humanitarian policy is recommended, relying on assistance of areas presenting risks, with the introduction of and adherence to rigorous measures of longitudinally integrated microbiological safety assurance. This model is equally applicable to other enteric diseases transmitted by food. Examples are given of how canned foods of neutral pH, fishery products, vegetables and certain fruits should be processed for safety. Importation monitoring strategies, linked to this proactive approach to consumer protection, are briefly summarized.

Cholera↗