Search

Molecular systematics is a remarkable approach for understanding the taxonomic traits and allows the exploration of the inter-population dynamics of several species in the Triatominae subfamily that are involved in Trypanosoma cruzi transmission. Compared to other relevant species that transmit vector-borne diseases, such as some species of the Diptera, there are relatively few nuclear genetic markers available for systematic studies in the Triatominae subfamily. Molecular systematic studies performed on Triatominae are based on mitochondrial gene fragments and, less frequently, on nuclear ribosomal genes or spacers. Due to the fact that these markers can occasionally present problems such as nuclear mitochondrial genes (NUMTs) or intra-genomic variation for high gene copy numbers, it is necessary to use additional nuclear markers to more reliably address the molecular evolution of Triatominae. In this study, we performed phylogenetic analysis using the nuclear elongation factor-1 alpha (EF-1α) gene in individuals from 12 species belonging to the Triatomini and Rhodniini tribes. Genetic diversities and phylogenetic topologies were compared with those obtained for the mitochondrial 16S rRNA and Cytochrome b (cyt b) genes, as well as for the D2 variable region of the ribosomal 28S rRNA gene. These results indicate that the EF-1α marker exhibits an intermediate level of diversity compared to mitochondrial and nuclear ribosomal genes, and that phylogenetic analysis based on EF-1α is highly informative for resolving deep phylogenetic relationships in Triatominae, such as tribe or genera., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Colombia is an endemic country for dengue fever where the four serotypes of virus dengue (DENV1-4) circulate simultaneously, and all types are responsible for dengue cases in the country. The control strategies are guided by entomological surveillance. However, heterogeneity in aedic indices is not well correlated with the incidence of the disease in cities such as Riohacha, Bello and Villavicencio. As an alternative, molecular detection of dengue virus in mosquitoes has been proposed as a useful tool for epidemiological surveillance and identification of serotypes circulating in field. We conducted a spatiotemporal fieldwork in these cities to capture adult mosquitoes to assess vector infection and explain the differences between Breteau indices and disease incidence. DENV infection in females and DENV serotype identification were evaluated and infection rates (IR) were estimated. The relationship between density, dengue cases and vector index was also estimated with logistic regression modeling and Pearson's correlation coefficient. The lack of association between aedic indices and dengue incidence is in agreement with the weak associations between the density of the mosquitoes and their infection with DENV in the three cities. However, association was evident between the IR and dengue cases in Villavicencio. Furthermore, we found important negative associations between temperature and lag time from two to six weeks in Riohacha. We conclude that density of mosquitoes is not a good predictor of dengue cases. Instead, IR and temperature might explain better such heterogeneity.

The emerging vector of Chagas disease, Triatoma maculata (Hemiptera, Reduviidae), is one of the most widely distributed Triatoma species in northern South America. Despite its increasing relevance as a vector, no consistent picture of the magnitude of genetic and phenetic diversity has yet been developed. Here, several populations of T. maculata from eleven Colombia and Venezuela localities were analyzed based on the morphometry of wings and the mitochondrial NADH dehydrogenase subunit 4 (ND4) gene sequences. Our results showed clear morphometric and genetic differences among Colombian and Venezuelan populations, indicating high intraspecific diversity. Inter-population divergence is suggested related to East Cordillera in Colombia. Analyses of other populations from Colombia, Venezuela, and Brazil from distinct eco-geographic regions are still needed to understand its systematics and phylogeography as well as its actual role as a vector of Chagas disease., (© 2016 The Society for Vector Ecology.)

The principal vector of Chagas disease in Central America, Triatoma dimidiata, shows considerable diversity of habitat, phenotype, and genotype across its geographic range (central Mexico to southern Ecuador), suggesting that it constitutes a complex of cryptic species. However, no consistent picture of the magnitude of ecological differentiation among populations of this complex has yet been developed. To assess ecological variation across the complex, we broadened the geographic coverage of phylogeographic data and analyses for the complex into Colombia and Mexico, with additional nuclear (ITS-2) and mitochondrial (ND4) DNA sequences. This information allowed us to describe distributions of previously documented clades in greater detail: Group I, from central Guatemala south to Ecuador; Group II, across Mexico south through the Yucatán Peninsula to Belize and northern Guatemala; and Group III, in northern Guatemala, Belize, and the Yucatán Peninsula. Using ecological niche modeling, we assessed ecological niche differentiation among the groups using four hypotheses of accessible areas (M) across the distribution of the complex. Results indicated clear niche divergence of Group I from Group II: the speciation process thus appears to have involved genetic and ecological changes, suggesting divergence in populations in response to environmental conditions., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Background: Aedes aegypti is the primary vector of the four serotypes of dengue virus (DENV1-4), Chikungunya and yellow fever virus to humans. Previous population genetic studies have revealed a particular genetic structure among the vector populations in the Americas that suggests differences in the ability to transmit DENV. In Colombia, despite its high epidemiologic importance, the genetic population structure and the phylogeographic depiction of Ae. aegypti, as well as its relationship with the epidemiologic landscapes in cities with heterogeneous incidence levels, remains unknown. We conducted a spatiotemporal analysis with the aim of determining the genetic structure and phylogeography of Colombian populations of Ae. aegypti among cities with different eco-epidemiologic characteristics with regard to DENV., Methods/findings: Mitochondrial cytochrome oxidase C subunit 1 (COI)--NADH dehydrogenase subunit 4 (ND4) genes were sequenced and analyzed from 341 adult mosquitoes collected during 2012 and 2013 in the Colombian cities of Bello, Riohacha and Villavicencio, which exhibit low, medium and high levels of incidence of DENV, respectively. The results demonstrated a low genetic differentiation over time and a high genetic structure between the cities due to changes in the frequency of two highly supported genetic groups. The phylogeographic analyses indicated that one group (associated with West African populations) was found in all the cities throughout the sampling while the second group (associated with East African populations) was found in all the samples from Bello and in only one sampling from Riohacha. Environmental factors such as the use of chemical insecticides showed a significant correlation with decreasing genetic diversity, indicating that environmental factors affect the population structure of Ae. aegypti across time and space in these cities., Conclusions: Our results suggest that two Ae. aegypti lineages are present in Colombia; one that is widespread and related to a West African conspecific, and a second that may have been recently introduced and is related to an East African conspecific. The first lineage can be found in cities showing a high incidence of dengue fever and the use of chemical insecticides, whereas the second is present in cities showing a low incidence of dengue fever where the use of chemical insecticides is not constant. This study helps to improve our knowledge of the population structure of Ae. aegypti involved in the diversity of dengue fever epidemiology in Colombia.

The Sierra Nevada de Santa Marta (SNSM) is a mountainous area in Colombia that is highly endemic to Chagas disease. We explored some eco-epidemiological attributes involved in the Chagas disease transmission scenario in three Indigenous communities. An epidemiological survey was done, where parasite infection in reservoirs and insects, Trypanosoma cruzi genotyping, identification of blood-meal sources in intradomiciliary insects using the high-resolution melting technique, and some risk factors were evaluated. The results suggest that several dwelling conditions such as thatched palm roofs and mud walls carried the highest risk of finding intradomiciliary Rhodnius prolixus, which 56.41% were infected with T. cruzi and fed with human blood. Moreover, T. cruzi Ia was the most frequent haplotype found in insects. These results indicate the existence of a domestic T. cruzi transmission cycle that does not overlap with the sylvatic cycle, and highlight the need for efficient entomological control focused to this area., (© The American Society of Tropical Medicine and Hygiene.)

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.

The Rhodnius Pacific group is composed of three species: Rhodnius pallescens, R. colombiensis and R. ecuadoriensis, which are considered important vectors of trypanosomes (Trypanosoma cruzi and T. rangeli) infecting humans. This group is considered as a recent trans-Andean lineage derived from the widespread distributed sister taxa R. pictipes during the later uplift of northern Andes mountain range. The widest spread species R. pallescens may be a complex of two divergent lineages with different chromosomal attributes and a particular biogeographical distribution across Central America and Colombia with several southern populations in Colombia occupying the same sylvatic habitat as its sister species R. colombiensis. Although the taxonomy of Rhodnius Pacific group has been well studied, the unresolved phylogenetic and systematic issues are the target of this paper. Here we explore the molecular phylogeography of this species group analyzing two mitochondrial (ND4 and cyt b) and one nuclear (D2 region of ribosomal 28S gene) gene sequences. The molecular analyses suggest an early divergence of the species R. ecuadoriensis and R. colombiensis, followed by a recent expansion of R. pallescens lineages. The phylogenetic relationship between sympatric R. pallescens Colombian lineage and R. colombiensis was further explored using wing morphometry, DNA genome size measurements, and by analyzing chromosomal behavior of hybrids progeny obtained from experimental crosses. Our results suggest that the diversification of the two R. pallescens lineages was mainly influenced by biogeographical events such as (i) the emergence of the Panama Isthmus, while the origin and divergence of R. colombiensis was associated with (ii) the development of particular genetic and chromosomal features that act as isolation mechanisms from its sister species R. pallescens (Colombian lineage). These findings provide new insights into the evolution of the Rhodnius Pacific group and the underlying biological processes that occurred during its divergence.

Background: Triatoma dimidiata is among the main vectors of Chagas disease in Latin America. However, and despite important advances, there is no consensus about the taxonomic status of phenotypically divergent T. dimidiata populations, which in most recent papers are regarded as subspecies., Methodology and Findings: A total of 126 cyt b sequences (621 bp long) were produced for specimens from across the species range. Forty-seven selected specimens representing the main cyt b clades observed (after a preliminary phylogenetic analysis) were also sequenced for an ND4 fragment (554 bp long) and concatenated with their respective cyt b sequences to produce a combined data set totalling 1175 bp/individual. Bayesian and Maximum-Likelihood phylogenetic analyses of both data sets (cyt b, and cyt b+ND4) disclosed four strongly divergent (all pairwise Kimura 2-parameter distances >0.08), monophyletic groups: Group I occurs from Southern Mexico through Central America into Colombia, with Ecuadorian specimens resembling Nicaraguan material; Group II includes samples from Western-Southwestern Mexico; Group III comprises specimens from the Yucatán peninsula; and Group IV consists of sylvatic samples from Belize. The closely-related, yet formally recognized species T. hegneri from the island of Cozumel falls within the divergence range of the T. dimidiata populations studied., Conclusions: We propose that Groups I-IV, as well as T. hegneri, should be regarded as separate species. In the Petén of Guatemala, representatives of Groups I, II, and III occur in sympatry; the absence of haplotypes with intermediate genetic distances, as shown by multimodal mismatch distribution plots, clearly indicates that reproductive barriers actively promote within-group cohesion. Some sylvatic specimens from Belize belong to a different species - likely the basal lineage of the T. dimidiata complex, originated ~8.25 Mya. The evidence presented here strongly supports the proposition that T. dimidiata is a complex of five cryptic species (Groups I-IV plus T. hegneri) that play different roles as vectors of Chagas disease in the region.

Rhodnius pallescens is considered the main vector of Chagas disease in Panama and a relevant secondary vector in northern Colombia. Previous data reported that this species presents cytogenetically heterogeneous populations, which are probably biogeographically segregated. To provide new information on the diversity of R. pallescens, we compared several populations from Colombia and Panama based on the morphometric analyses of wings, mitochondrial cytochrome b (cyt b) gene sequencing, and genomic DNA measurements. Although no differences in DNA amount were detected, significant differences in cyt b sequences as well as wing size and shape were identified among populations. The results obtained in this work indicate R. pallescens comprises two evolutionary lineages with genetic and morphological differences that could be explained by their geographic isolation in distinct ecological zones. These results provide new insight into R. pallescens population diversity and the underlying biological processes that shape its evolution., (Copyright © 2012. Published by Elsevier B.V.)

In Triatominae, "robustus" group constitutes a cluster of species with great haplotypic divergences but high similarities at morphological and nuclear DNA levels. Given these similarities, species identification generates a frequently problematic issue. In northwestern Amazonia, Rhodnius robustus cohabit with an apparently new species, cryptic with R. robustus (Abad-Franch and Monteiro, 2005). In this region (municipality of Puerto Asís, Department of Putumayo, Colombia), we collected insects classified as R. robustus by traditional keys. We compared this sample with specimens of R. robustus from Venezuela, and of R. prolixus from Colombia and Venezuela. The comparisons used landmark-based geometric morphometrics, and analyses of mitochondrial cytochrome b gene and of D2 variable region of the 28S RNA. The shape of the wings from Puerto Asís specimens disclosed clear-cut divergence from the shape of the wings as found for R. prolixus specimens from Venezuela and Colombia, and diverged from the shape of R. robustus from Venezuela. Thus, morphometric analyses suggested that the Puerto Asís collection could represent a new taxon. Using R. pallescens as an outgroup, a tentative phylogenetic tree based on the geometry of the wing showed the Rhodnius from Puerto Asís more similar to the R. prolixus from Colombia than their congeners from Venezuela. In contrast, the molecular classification clustered Colombian R. prolixus and Venezuelan R. robustus with published GenBank sequences, but it gave the insects from Puerto Asís a basal position to the "robustus" group. This outcome suggests that the Puerto Asís haplotype could be the one found by Abad-Franch and Monteiro (2005). Thus, both morphometric and molecular markers used here, although differing in the phylogenetic classification of samples, could differentiate the Puerto Asís sample from the morphologically similar R. prolixus and R. robustus. This could represent a valuable help in the entomological surveillance related to the control of Chagas disease in the South of Colombia and North of Ecuador., (Copyright © 2011 Elsevier B.V. All rights reserved.)

Introduction: Information concerning to triatomine diversity and some eco-epidemiologic aspects on Margarita Island has been recorded only from two of the five counties on the island. Knowledge about species habitat and their natural infection is essential to establish the risk for Chagas disease in endemic areas., Objective: The distribution of triatomine insect fauna and its infection with Trypanosoma cruzi was described in order to establish and to stratify the risk of Chagas disease transmission., Material and Methods: Each of the 5 counties on Margarita Island were surveyed for triatomid insects inside and outside each dwelling. In the extradomicilary area, searches were conducted in the palms and bird nests located within forests and in pastures near domiciles. Infection with T. cruzi was determined amplifying by PCR the DNA extracted from triatomine feces., Results: Five species of Reduviidae were recovered among the 1,154 triatomines captured in the 5 counties. Triatoma maculata and Rhodnius pallescens showed high infection rates within dwellings and as well as in the peridomestic areas in Mompós and Talaigua Nuevo. On the palm trees, only R. pallescens and Eratyrus cuspidatus were found infected, and only in San Fernando and Margarita. In Cicuco, only R. pallescens was infected. Presence of Triatoma dimidiata was also ascertained., Conclusion: Infected triatomines were present in houses and on palm trees in all counties on the island. These observations indicate a potential risk of Chagas across the entire island; furthermore the presence of T. dimidiata, a very efficient Chagas vector, emphasizes the need to establish its epidemiological status on the island.

Rhodnius pallescens is the main vector of Trypanosoma cruzi in Panama and one of the most relevant secondary vectors in Colombia. Despite the importance of this species, there is limited knowledge about the genetic variability along its geographical distribution. In order to evaluate the degree of karyotype variability we analyzed the meiotic behavior and banding pattern of the chromosomes of 112 males of R. pallescens coming from different regions of Colombia and Panama. Using the C-banding technique we identified two chromosomal patterns or cytotypes characterized by differences in the amount, size and distribution of constitutive heterochromatic regions in the chromosome complement (2n = 20 autosomes plus XY in males). The individuals can be easily classified in each cytotype by the analysis of the chromosomes during first meiotic prophase. The frequencies of the cytotypes are variable according to the geographic origin of the populations. This chromosomal divergence together with morphological data supports the existence of three genetically different populations of R. pallescens and provides new information to understand the distribution dynamics of this species.