Reconstructing Native American population history.

The peopling of the Americas has been the subject of extensive genetic, archaeological and linguistic research; however, central questions remain unresolved. One contentious issue is whether the settlement occurred by means of a single migration or multiple streams of migration from Siberia. The pattern of dispersals within the Americas is also poorly understood. To address these questions at a higher resolution than was previously possible, we assembled data from 52 Native American and 17 Siberian groups genotyped at 364,470 single nucleotide polymorphisms. Here we show that Native Americans descend from at least three streams of Asian gene flow. Most descend entirely from a single ancestral population that we call 'First American'. However, speakers of Eskimo-Aleut languages from the Arctic inherit almost half their ancestry from a second stream of Asian gene flow, and the Na-Dene-speaking Chipewyan from Canada inherit roughly one-tenth of their ancestry from a third stream. We show that the initial peopling followed a southward expansion facilitated by the coast, with sequential population splits and little gene flow after divergence, especially in South America. A major exception is in Chibchan speakers on both sides of the Panama isthmus, who have ancestry from both North and South America.

Interrogating the transmission dynamics of Trypanosoma cruzi (Trypanosomatida, Trypanosomatidae) by Triatoma venosa (Hemiptera: Reduviidae) after the elimination of vector transmission by Rhodnius prolixus in Boyacá eastern Colombia.

Chagas disease (CD) is a parasitic zoonosis (Trypanosoma cruzi) that is endemic in Colombia. Vector control of Rhodnius prolixus, the main domestic T. cruzi vector, has been achieved in a large part of the area with historically vector transmission of CD. It is necessary to understand the ecological behavior characteristics of local native vectors to ensure sustainability of the vector control programs. To evaluate the long-term success of a recent vector control campaign in the Boyacá department (Colombia), we used a combined strategy of entomological surveillance with co-existing canine surveillance from ten rural villages within six municipalities of the Tenza valley region (Boyacá, Colombia): Chinavita, Garagoa, Guateque, Somondoco, Sutatenza and Tenza, with historical reports of R. prolixus and secondary vectors. Collected triatomines and canine whole blood were analyzed for T. cruzi infection and genotyping. Triatomine bugs specimens were evaluated for blood meal source. Canine serology was performed using two distinct antibody assays. In total, 101 Triatoma venosa were collected by active search in domestic and peridomestic habitats. A natural infection prevalence of 13.9% (14/101) and four feeding sources were identified: human, dog, rat, and hen. A frequency infection of 46.5% (40/87) was observed from two independent serological tests and T. cruzi DNA was detected in 14 dogs (16.4%). Only TcIsylvatic DTU was detected. The results suggest that T. venosa present eco-epidemiological characteristics to maintain the transmission of T. cruzi in Tenza valley. This species has reinfested the intervened households and it has an active role in domestic and peridomestic transmission of T. cruzi due to their infection rates and feeding behavior. Therefore, this species should be considered as epidemiologically relevant for vector control strategies. Moreover, there is a need for human serological studies to have a close up of risk they are exposed to.

ProtozoaDB: dynamic visualization and exploration of protozoan genomes.

ProtozoaDB (http://www.biowebdb.org/protozoadb) is being developed to initially host both genomics and post-genomics data from Plasmodium falciparum, Entamoeba histolytica, Trypanosoma brucei, T. cruzi and Leishmania major, but will hopefully host other protozoan species as more genomes are sequenced. It is based on the Genomics Unified Schema and offers a modern Web-based interface for user-friendly data visualization and exploration. This database is not intended to duplicate other similar efforts such as GeneDB, PlasmoDB, TcruziDB or even TDRtargets, but to be complementary by providing further analyses with emphasis on distant similarities (HMM-based) and phylogeny-based annotations including orthology analysis. ProtozoaDB will be progressively linked to the above-mentioned databases, focusing in performing a multi-source dynamic combination of information through advanced interoperable Web tools such as Web services. Also, to provide Web services will allow third-party software to retrieve and use data from ProtozoaDB in automated pipelines (workflows) or other interoperable Web technologies, promoting better information reuse and integration. We also expect ProtozoaDB to catalyze the development of local and regional bioinformatics capabilities (research and training), and therefore promote/enhance scientific advancement in developing countries.

Identification and characterization of two novel lysozymes from Rhodnius prolixus, a vector of Chagas disease.

Lysozymes have been described in invertebrates as digestive or immune molecules. We report here the characterization of two novel c-type lysozymes, RpLys-A (EU250274) and RpLys-B (EU250275), isolated from the fat body and digestive tract of immune stimulated Rhodnius prolixus, a major vector of Chagas disease. Transcriptional profiles indicate that the temporal and spatial expression patterns of these two peptides are very different. RpLys-A is expressed predominantly in the midgut after ingestion of Trypanosoma cruzi in a bloodmeal, or after injection of bacteria into the hemocoel. RpLys-B is expressed primarily in the fat body after bacterial injection. Phylogenetic alignments indicate that RpLys-A aligns best with molecules from other hemipterans whose major expression is found in the intestinal tract whereas RpLys-B aligns best with mosquito and tick molecules whose expression is found principally in hemocytes and fat body and whose role has been described as immune-related. These data suggest a differential compartmentalized role of two closely related molecules; one for immunity in the hemocoel and the other for digestion in the midgut.

[Molecular and immunological analyses suggest the absence of hydrophilic surface proteins in Leishmania (Viannia) panamensis]. / El análisis molecular y el inmunogénico sugieren la ausencia de las proteínas hidrofílicas de superficie en Leishmania (Viannia) panamensis.

INTRODUCTION: The genus Leishmania is divided into two subgenera: Leishmania and Viannia. The two subgenera present several important differences such as the pathology they cause in susceptible hosts, their in vitro growth behavior, their genetic characteristics, and the expression pattern of several proteins, including those of the hydrophilic surface protein family. OBJECTIVE: To characterize the hydrophilic surface protein family in Leishmania (Viannia) panamensis. MATERIALS AND METHODS: The hasp genes were amplified in L. (V.) panamensis, using specific primers previously designed to amplify this gene in Leishmania (Leishmania) major. The PCR products were cloned, sequenced, and the sequences analyzed using common bioinformatics tools. Secondly, a serological screening was undertaken with an enzyme-linked immunosorbent assay and Western blot to detect specific antibodies against the hydrophilic surface recombinant protein from L. (L.) major. RESULTS: A copy of a pseudogene was amplified in L. (V.) panamensis which was 60% homologous with the L. (L.) major orthologous gene. Antibodies responded to the hydrophilic surface recombinant proteins only in sera from patients with visceral leishmaniasis [Leishmania (Leishmania) chagasi]. CONCLUSION: These results suggest the lack of a functional hasp gene in L. (V.) panamensis, suggesting probably the loss of the complete gene family in this species of the Viannia subgenus.

Identifying four Trypanosoma cruzi I isolate haplotypes from different geographic regions in Colombia.

Trypanosoma cruzi has been classified into the groups T. cruzi I and T. cruzi II. The latter is subdivided into five smaller lineages based on multilocus enzyme electrophoresis and random amplified polymorphic DNA, designated as IIa-IIe, which shows correspondence with rRNA/mini-exon lineages. Twelve previously characterised T. cruzi isolates from different hosts, including humans, Didelphis marsupialis, and triatomines were analysed to establish genetic variability in T. cruzi group T. cruzi I isolates from different geographical regions of Colombia. DNA samples were sequenced based on the mini-exon gene intergenic region. Sequences were analysed using Clustal W, Staden 1.5 and MEGA3 software, and using reported sequences from the GenBank as reference. The genetic distances were analysed using Kimura's two-parameter model. The isolates' joint alignment was of 350bp, and the calculated nucleotide divergence was of 17.5%. The differences consisted of 23 transitions (7.2%), 14 transversions (4.4%) and 19 insertion-deletions (5.9%). The Colombian T cruzi I isolates revealed sufficient genetic variability for us to propose the existence of four haplotypes identified through single nucleotide polymorphism (SNP) and insertion/deletion found in the mini-exon gene's non-transcribed spacer intergenic region.

[Biological and genetic characterization of two Colombian clones of Trypanosoma cruzi groups I and II]. / Caracterización biológica y genética de dos clones pertenecientes a los grupos I y II de Trypanosoma cruzi de Colombia.

INTRODUCTION: Genetic differences between T. cruzi I and T. cruzi ll may determine differences in their tissue tropism in the vertebrate host and may also be responsible for the differences in clinical manifestations of Chagas disease. OBJECTIVE: Two Colombian clones of the T. cruzi groups I and II were characterized biologically and genetically in a murine model. MATERIALS AND METHODS: Strains Cas15 and AF1 belonging to the T. cruzi groups I and II were cloned in semisolid medium. A clone of each strain and a mix of both were used to infect mice; the mice were subsequently sacrificed at selected post-infection intervals. In order to identify the parasite presence in blood and organs, two methods were used (a) microhematocrit and (b) polymerase chain reaction with primers for satellite DNA and the intergenic region of miniexon. RESULTS: The T. cruzi I clone was more infectious, with a preferential tropism observed in heart, rectum and skeletal muscle, whereas clone T. cruzi II exhibited a preferential tropism for spleen and liver. During the infection with the clone mixture a predominance of the T. cruzi I clone over clone II in blood as well as in organs was observed. CONCLUSIONS: The results corroborate that the genetic differences between the T. cruzi groups correlate with their tissue tropism, and can play an essential role in explaining the clinical manifestations of Chagas disease observed in Colombia.

[Myocardial cellular damage and the activity of the mitochondrial ATP synthase in rats infected with a Colombian strain of Trypanosoma cruzi]. / Lesión celular del miocardio y actividad de la ATPsintasa mitocondrial en ratas infectadas con una cepa colombiana de Trypanosoma cruzi.

INTRODUCTION: Chagas disease is the main cause of cardiomyopathy in endemic regions of Latin America. Alterations in the cardiac mitochondrial energy metabolism caused by Trypanosoma cruzi can be involved in the development of this cardiomyopathy during the course of Chagas disease. OBJECTIVE: The cellular injury of the rat myocardium was investigated in rats infected with the Colombian Mg8 strain of Trypanosoma cruzi. The activity of mitochondrial ATP synthase was measured to determine the relationship heart damage with the energy metabolism. MATERIALS AND METHODS: Two groups of five rats each were infected with tripomastigotes, with 1 group of 6 rats serving as controls. The course of infection was characterized by parasitological, histopathological and molecular studies. The mitochondrial ATP synthase activity of the myocardium was evaluated in all rats. RESULTS: Peak parasitaemia (day 26 post infection) and the time of parasite clearance from circulating blood (day 60 post infection) were determined for acute and chronic phase models. The histopathological and molecular results showed that the Colombian Mg8 strain has tropism to the cardiac tissue and causes considerable cellular injury of the myocardium in rats during both phases. Despite the lesions observed in infected rats, no statistical difference in the activity of the mitochondrial ATPsynthase was observed between them and the non-infected rats. CONCLUSION: Mitochondrial energy metabolism of the cardiomyocites does not appear to change during cellular injury of rat myocardium associated with infection by the Colombian Mg8 T. cruzi strain.

[Analysis of polymorphisms in the trypanothione reductase and cruzipain genes in Colombian strains of Trypanosoma cruzi]. / Análisis de polimorfismos en los genes tripanotión reductasa y cruzipaína en cepas colombianas de Trypanosoma cruzi.

INTRODUCTION: Genetic studies of Trypanosoma cruzi have tried to establish relations between genetic variants and their biological characteristics, such as clinical manifestations, host or geographic origin. However, much controversy exists on the associations between the commonly used DNA markers with group, clinical characteristics and disease epidemiology. OBJECTIVE: In this study determined the variability of the genes that code for the proteins trypanothione reductase and cruzipain, both involved in the infection and survival of the parasite in the mammalian host, was studied and the association between genetic polymorphism and biological and geographic sources in Colombian T. cruzi strains was examined. MATERIALS AND METHODS: The genotypes for each of six SNPs (single nucleotide polymorphisms) for trypanothione reductase and eight SNPs for cruzipain genes were identified by polymerase chain reaction-restriction fragment length polymorphism in 36 T. cruzi Colombian stocks from several regions and biological origins. RESULTS: Three genotypes were identified for trypanothione reductase with Acy I and Hae III enzymes and six genotypes for cruzipain with the Rsa I, Ban I and Bsu 361 enzymes. CONCLUSIONS: For trypanothione reductase, an association was not established with biological or geographical origin; however, alleles at positions 102 and 210 allowed discrimination with groups I and II. For cruzipain, specific genotypes were associated with group, biological and geographic origin. The usefulness of molecular markers on these genes was demonstrated for the determination and differentiation of genetic varieties in T. cruzi.

[Seroprevalence of Chagas disease and associated risk factors in a population of Morroa, Sucre]. / Seroprevalencia de la enfermedad de Chagas y factores de riesgo asociados en una población de Morroa, Sucre.

INTRODUCTION: Chagas disease is a major public health problem in Latin America. In Colombia, a large area has the ecoepidemiological conditions which favor the active transmition of this infection. OBJECTIVE: This study was undertaken in a population from the municipality of Morroa, Sucre Province, to evaluate risk factors and to determine the seroprevalence to Chagas disease. MATERIALS AND METHODS: A questionnaire was given to a sample population of 122 people classed as rural (n=76) or urban area (n=46). A serological screening was undertaken by Elisa test, with confirmation of seropositives with IHA (Chagatest) and parasitological confirmation by polymerase chain reaction (PCR). RESULTS: Four people were positive by Elisa test (3.3%); however, they were negative by IHA and PCR. One of the four positives by Elisa was positive by indirect immuno flourescence (IFAT) as well. The sample showed a low presence of seropositives against Trypanosoma cruzi. However, the presence of parasite could not be confirmed by the PCR test. The main risk factors were houses thatched with palm roofs, clay floors, wood walls, and presence of domestic animal reservoirs. CONCLUSIONS: The study population presented risk factors for the establishment of active transmission. The presence of triatomines must be verified in this area and establishment of control measures are necessary for preventiving the resurgence of the Chagas disease in Morroa.

[Trypanosoma rangeli parasite-vector-vertebrate interactions and their relationship to the systematics and epidemiology of American trypanosomiasis]. / Interacción tripanosoma-vector-vertebrado y su relación con la sistemática y la epidemiología de la tripanosomiasis Americana.

INTRODUCTION: Trypanosoma rangeli is a species of trypanosome second to T. cruzi, that is infective to humans in Latin America. Variability in the biological, biochemical and molecular characteristics between different isolates isolates of this parasite have been recorded. OBJECTIVE: Morphological and molecular characteristics were recorded from strains of T. rangeli that were isolated from different species of Rhodnius and maintained in different vertebrate species. MATERIALS AND METHODS: Nineteen strains of T. rangeli were isolated from R. prolixus, R. pallescens and R. colombiensis in Colombia, R. ecuadoriensis in Peru and R. pallescens in Panama. Polymorphism of blood trypomastigotes in ICR mice was evaluated and pleomorphism of P53 strain of T. rangeli KP1(-) inoculated in mouse, marsupial and canine was studied. RAPD analysis (randomly amplified polymorphic DNA analysis) of 12 strains isolated from four species of Rhodnius was performed. RESULT: Based on the total length of blood trypomastigotes, three discrete groups were observed. The P53 strain showed significant differences in the size of blood trypomastigotes in mouse, marsupial and canine. RAPD analysis showed that the strains segregated into two branches corresponding to strains of T. rangeli KP1(+) and T. rangeli KP1(-). All strains of T. rangeli KP1(-) clustered according to the species of Rhodnius from which they were isolated. CONCLUSION: These data reveal, for the first time, a close association amongst T. rangeli strains and Rhodnius species, confirming that each species of Rhodnius transmits to vertebrate hosts a parasite population with clear phenotypic and genotypic differences. This is further evidence that supports the concept of clonal evolution of these parasites.

Aedes albopictus (Skuse, 1894) infected with the American-Asian genotype of dengue type 2 virus in Medellín suggests its possible role as vector of dengue fever in Colombia.

INTRODUCTION: Aedes aegypti and Ae. albopictus are recognized vectors of dengue, yellow fever, chikungunya and Zika arboviruses in several countries worldwide. In Colombia, Ae. albopictus geographical distribution has increased to include highly populated cities such as Cali and Medellín. Although this species has been frequently found in urban and semi-urban zones in the country, its role as vector of the dengue fever is poorly known. OBJECTIVE: To identify the presence of Ae. albopictus specimens naturally infected with dengue virus collected in Medellín. MATERIALS AND METHODS: Insects were collected in the Universidad Nacional de Colombia campus in Medellín. Individuals were classified as Ae. albopictus and confirmed by DNA barcode region analysis. Mosquitoes were processed for dengue virus identification, and a fragment of the NS3 gen was sequenced and compared with DENV-2 genotypes reported in the literature. RESULTS: Sequence analysis of COI indicated Ae. albopictus individuals were similar to those recently reported in Colombia, and genetically close to those from other regions worldwide. Among the pools tested one was positive for DENV-2, and the NS3 analysis indicated it belonged to the Asian-American clade. CONCLUSION: We report the presence Ae. albopictus naturally infected with the Asian-American genotype of DENV-2 in Colombia. The presence of Ae. albopictus specimens carrying the most common genotype infecting humans in a highly populated city such as Medellín indicates its potential role as dengue vector in Colombia and highlights the relevance of including it in current vector surveillance strategies.

Curvas de fusión de regiones genómicas específicas: una herramienta prometedora para el diagnóstico y tipificación de las especies causantes de la leishmaniasis cutánea en Colombia.

Introducción. La leishmaniasis cutánea es una enfermedad causada por parásitos del género Leishmania que tiene gran incidencia en Colombia. El diagnóstico y la identificación de la especie infecciosa son factores críticos en el momento de escoger e iniciar el tratamiento. Actualmente, los métodos de diagnóstico y tipificación requieren procedimientos complejos, por lo que es necesario validar nuevos marcadores moleculares y métodos que simplifiquen el proceso.Objetivo. Desarrollar una herramienta basada en la reacción en cadena de la polimerasa (PCR) con curvas de fusión (High Resolution Melting; PCR-HRM) para el diagnóstico y tipificación de las tres especies de Leishmania de importancia epidemiológica en casos de leishmaniasis cutánea en Colombia.Materiales y métodos. Los genomas de Leishmania panamensis, L. braziliensis y L. guyanensis se compararon mediante métodos bioinformáticos. Las regiones específicas de especie identificadas se validaron mediante PCR. Para los marcadores seleccionados se diseñó una PCR-HRM y se estimaron algunos parámetros de validez y seguridad usando aislamientos de pacientes colombianos caracterizados previamente mediante PCR y análisis de polimorfismos en la longitud de los fragmentos de restricción (Restriction Fragment Length Polymorphism - RFLP; PCR-RFLP) del gen hsp70.Resultados. El análisis genómico comparativo mostró 24 regiones específicas de especie. Sin embargo, la validación mediante PCR solo identificó un marcador específico para cada especie de Leishmania. Los otros marcadores mostraron amplificación cruzada. El límite de detección para los tres marcadores seleccionados fue de un parásito, mientras que la sensibilidad, la especificidad, el valor predictivo positivo y el negativo fueron de 91,4, 100, 100 y 75 %, respectivamente.Conclusiones. Las tres regiones seleccionadas pueden emplearse como marcadores moleculares en el diagnóstico y tipificación de las especies causantes de la leishmaniasis cutánea en Colombia.

Virological surveillance of Aedes (Stegomyia) aegypti and Aedes (Stegomyia) albopictus as support for decision making for dengue control in Medellín.

INTRODUCTION: Dengue represents an important public health problem in Colombia. No treatment is available and the vaccine has not been approved in all countries, hence, actions should be strengthened to mitigate its impact through the control of Aedes aegypti, the vector mosquito. In Colombia, surveillance is done using entomological indexes and case notification, which is usually informed late, leading to untimely interventions. Viral detection in urban mosquitoes using molecular techniques provides more accurate entomological information for decision-making. OBJECTIVE: To report results of virological surveillance in Aedes specimens collected during routine entomological activities of the Secretaría de Salud de Medellín. MATERIALS AND METHODS: Specimens were collected during two periods in each of which we selected 18 dwellings around each one of the 250 larva traps arranged for mosquitoe surveillance, as well as 70 educational institutions and 30 health centers. Specimens were identified morphologically, and divided in pools for viral detection using reverse transcription polymerase chain reaction (RT-PCR). We calculated the minimum infection rate and the adult infestation index for each group. RESULTS: We collected 1,507 adult mosquitoes, 10 of which were identified as A. albopictus. Out of the 407 pools, 132 (one of them Ae. albopictus) were positive, and 14.39% were A. aegypti males. The minimum infection rates for Ae. aegypti were 120.07 and 69,50 for the first and second periods, respectively, and the adult infestation index was higher in educational institutions (23.57%). CONCLUSIONS: Using RT-PCR we identified natural infectivity and vertical transmission of dengue virus in A. aegypti and A. albopictus. We suggest the use of molecular techniques in arbovirosis surveillance and control programs in Colombia.

Autosomal microsatellite data from Northwestern Colombia.

Allele frequencies and some forensic parameters for 12 autosomal microsatellites (CSF1PO, TPOX, THO1, VWA, D16S539, D7S820, D13S317, D5S818, F13A1, FESFPS, F13B, LPL) were estimated from three departments from Northwestern Colombia. The total number of samples analysed was 1045 individuals. Comparative analysis among the three studied departments and with other published Colombian populations were also performed and discussed.

[Genetic variability of Trypanosoma cruzi in blood and organs of infected mice determined by LSSP-PCR]. / Análisis por LSSP-PCR de la variabilidad genética de Trypanosoma cruzi en sangre y órganos de ratones.

BACKGROUND: Chagas' disease, caused by Trypanosoma cruzi, has a variable clinical course, ranging from asymptomatic infection to chronic disease. Trypanosoma cruzi has a clonal population structure, although infecting strains are often multiclonal. Genetic variability of T. cruzi may be one of the determinant factors in differential tissue tropism and consequently of the clinical forms of the disease. OBJECTIVE: To examine this possibility, mice were infected with two Colombian T. cruzi strains to determine the distribution of genetic variants in blood and organs. The sensitivity of three molecular markers was evaluated, and the genetic variability of the clones was determined. The latter was attained by means of low-stringency single specific primer polymerase chain reaction (LSSP-PCR) using a kinetoplast DNA (kDNA) marker. The kDNA signatures obtained with the LSSP-PCR were analyzed by neighbor-joining. RESULTS AND CONCLUSION: The presence of the two lineages of T. cruzi was confirmed, as well as the multiclonal character of the two strains. The most sensitive marker was the kDNA. The most affected organ was the heart, which showed the greatest number of positive results with the three markers. Genetic differences were noted between the clones from the blood and organs of infected mice. These results support the value of the LSSP-PCR technique for the study of the molecular epidemiology of Chagas' disease.

Parity between kinetoplast DNA and mini-exon gene sequences supports either clonal evolution or speciation in Trypanosoma rangeli strains isolated from Rhodnius colombiensis, R. pallescens and R. prolixus in Colombia.

Trypanosoma rangeli are kinetoplastid protozoa which have been largely recognized and defined in several Latin American countries in relation to T. cruzi, because the two trypanosome species are frequently found in mixed infections in triatominae vectors, humans and a variety of wild and domestic mammals. We report the molecular characterization of 18 T. rangeli strains isolated from the salivary glands of naturally infected Rhodnius colombiensis, R. pallescens and R. prolixus by using two independent set of molecular markers. kDNA and mini-exon amplification indicated dimorphism within both DNA sequences: KP1, KP2 and KP3 or KP2 and KP3 products for kDNA mini-circles and 380 or 340bp products for the mini-exon. One of two associations was observed within individual strains: KP1, KP2 and KP3 kDNA products with the 340bp mini-exon product and the KP2 and KP3 kDNA products with the 380bp mini-exon product. Independent mitochondrial and nuclear molecular markers showed a clear division of T. rangeli into two major phylogenetic groups associated with specific vectors in Colombia and in other Latin America countries. These results support either clonal evolution or speciation in T. rangeli populations, probably derived as a secondary adaptation to their parasitic condition in triatomine vectors.

Molecular evidence of demographic expansion of the chagas disease vector Triatoma dimidiata (Hemiptera, Reduviidae, Triatominae) in Colombia.

BACKGROUND: Triatoma dimidiata is one of the most significant vectors of Chagas disease in Central America and Colombia, and, as in most species, its pattern of genetic variation within and among populations is strongly affected by its phylogeographic history. A putative origin from Central America has been proposed for Colombian populations, and high genetic differentiation among three biographically different population groups has recently been evidenced. Analyses based on putatively neutral markers provide data from which past events, such as population expansions and colonization, can be inferred. We analyzed the genealogies of the nicotinamide adenine dinucleotide dehydrogenase 4 (ND4) and the cytochrome oxidase subunit 1-mitochondrial genes, as well as partial nuclear ITS-2 DNA sequences obtained across most of the eco-geographical range in Colombia, to assess the population structure and demographic factors that may explain the geographical distribution of T. dimidiata in this country. RESULTS: The population structure results support a significant association between genetic divergence and the eco-geographical location of population groups, suggesting that clear signals of demographic expansion can explain the geographical distribution of haplotypes of population groups. Additionally, empirical date estimation of the event suggests that the population's expansion can be placed after the emergence of the Panama Isthmus, and that it was possibly followed by a population fragmentation process, perhaps resulting from local adaptation accomplished by orographic factors such as geographical isolation. CONCLUSION: Inferences about the historical population processes in Colombian T. dimidiata populations are generally in accordance with population expansions that may have been accomplished by two important biotic and orographic events such as the Great American Interchange and the uplift of the eastern range of the Andes mountains in central Colombia.

Specific primers design based on the superoxide dismutase b gene for Trypanosoma cruzi as a screening tool: Validation method using strains from Colombia classified according to their discrete typing unit.

OBJECTIVE: To classify 21 new isolates of Trypanosoma cruzi (T. cruzi) according to the Discrete Typing Unit (DTU) which they belong to, as well as tune up a new pair of primers designed to detect the parasite in biological samples. METHODS: Strains were isolated, DNA extracted, and classified by using three Polymerase Chain Reactions (PCR). Subsequently this DNA was used along with other isolates of various biological samples, for a new PCR using primers designed. Finally, the amplified fragments were sequenced. RESULTS: It was observed the predominance of DTU I in Colombia, as well as the specificity of our primers for detection of T. cruzi, while no band was obtained when other species were used. CONCLUSIONS: This work reveals the genetic variability of 21 new isolates of T. cruzi in Colombia.Our primers confirmed their specificity for detecting the presence of T. cruzi.

[Investigation of vectors and reservoirs in an acute Chagas outbreak due to possible oral transmission in Aguachica, Cesar, Colombia]. / Investigación de vectores y reservorios en brote de Chagas agudo por posible transmisión oral en Aguachica, Cesar, Colombia.

Colombia recorded 11 cases of acute Chagas disease and 80 cases of oral contamination with Trypanosoma cruzi. The current study analyzes the entomological and parasitological characteristics of the outbreak in Aguachica, Cesar Department, in 2010. An interdisciplinary group of health professionals and regional university personnel conducted the laboratory tests in the patients and the investigation of the transmission focus. Eleven cases of acute Chagas diseases were detected in a single family in a dwelling with domiciliated triatomines and Rhodnius pallescens, Pantrongylus geniculatus, Eratyrus cuspidatus, and two Didelphis marsupialis opossums infected with T. cruzi in Attalea butyracea and Elaeis oleifera palm trees in the urban area of Aguachica. The study analyzes the role of R. pallescens and palm trees in the wild cycle of T. cruzi and in oral transmission of Chagas disease. Sporadic incursions by wild R. pallescens, P. geniculatus, and E. cuspidatus from the nearby palm trees into human dwellings may cause increasingly frequent outbreaks of oral Chagas disease.