RESUMO
Triatoma dimidiata (Latreille 1811) is considered the second most important vector of the Trypanosa cruzi etiological agent of Chagas disease in Colombia. It has a life cycle that involves a domiciled, peridomiciled, and wild distribution. The study of feeding behavior and its influence on the survival of sylvatic and peridomestic populations can help identify a possible differential risk in the transmission of Chagas disease to humans, mainly in northwestern and east-central Colombia. We characterize the main parameters of feeding behavior and their influence on the longevity and survival of two rat-fed populations of T. dimidiata from Colombia, one in the north-west (from palms in a tropical dry forest area) and the other in the center-east (peridomiciliated), under controlled environmental conditions. The palm population took considerably longer than the peridomestic population to complete its life cycle under experimental laboratory conditions, being both populations univoltine since they have only one life cycle per year. Statistically significant differences were evidenced using Box-Cox model between the survival rates of T. dimidiata populations when the parameters related to blood intake and behavior were incorporated, in contrast to the survival models in which the origin only was considered as a factor. Our results could be used to generate recommendations to guide prevention strategies in communities near sylvatic and peridomiciliated populations of T. dimidiata.
Assuntos
Comportamento Alimentar , Triatoma , Animais , Humanos , Ratos , Doença de Chagas/prevenção & controle , Meio Ambiente , Longevidade , Doenças dos Roedores , Triatoma/fisiologia , Trypanosoma cruziRESUMO
Triatoma dimidiata (Hemiptera: Reduviidae) is a secondary vector of Trypanosoma cruzi in Colombia and represents an important epidemiological risk mainly in the central and oriental regions of the country where it occupies sylvatic, peridomestic, and intradomestic ecotopes, and because of this complex distribution, its distribution and abundance could be conditioned by environmental factors. In this work, we explored the relationship between T. dimidiata distribution and environmental factors in the northwest, northeast, and central zones of Colombia and developed predictive models of infestation in the country. The associations between the presence ofT. dimidiata and environmental variables were studied using logistic regression models and ecological niche modeling for a sample of villages in Colombia. The analysis was based on the information collected in field about the presence ofT. dimidiata and the environmental data for each village extracted from remote sensing images. The presence of Triatoma dimidiata(Latreille, 1811) was found to be significantly associated with the maximum vegetation index, minimum land surface temperature (LST), and the digital elevation for the statistical model. Temperature seasonality, annual precipitation, and vegetation index were the variables that most influenced the ecological niche model ofT. dimidiata distribution. The logistic regression model showed a good fit and predicted suitable habitats in the Andean and Caribbean regions, which agrees with the known distribution of the species, but predicted suitable habitats in the Pacific and Orinoco regions proposing new areas of research. Improved models to predict suitable habitats forT. dimidiata hold promise for spatial targeting of integrated vector management.
Assuntos
Doença de Chagas/epidemiologia , Meio Ambiente , Insetos Vetores , Triatoma , Animais , Doença de Chagas/transmissão , Colômbia/epidemiologia , Demografia , Ecossistema , Humanos , Insetos Vetores/parasitologia , Modelos Estatísticos , Imagens de Satélites , Triatoma/parasitologiaRESUMO
Triatoma dimidiata Latreille is the second most important vector of Chagas' disease in Colombia and is found in urban and periurban areas. From January 2007 to June 2008, we performed field work in 8 departments, 18 municipalities, and 44 rural villages, covering most of its known distribution and all of its ecological zones in the country. The goal was to determine the geographical distribution, the ecology, and house infestation indices of T. dimidiata over its range and hence the Chagas' disease transmission risk. In Colombia, T. dimidiata occupies a wide variety of ecosystems, from transformed ecosystems in the Andean biome with shrub and xerofitic vegetation to very dense forests in the humid tropical forests in the Sierra Nevada of Santa Marta. According to genetic and ecological criteria, at least two T. dimidiata forms of this species are present: populations from the northwest of the country (Caribbean plains) are restricted to palm tree habitats, and domestic involvement is limited to sporadic visits because of attraction by light; and populations of the east region (Andean mountains) presenting a complex distributional pattern including sylvatic, peridomestic, and domiciliated ecotopes, and occupying a great variety of life zones. The latter population is of epidemiological importance due to the demonstrated migration and genetical flow of individuals among the different habitats. Control, therefore, must take into account its diversity of habitats.
Assuntos
Triatoma , Animais , Colômbia , Ecossistema , GeografiaRESUMO
INTRODUCTION: For the first time we provide the description of the melanic (dark) morphotype of Rhodnius nasutus and determine the pattern of genetic inheritance for this characteristic. METHODS: Dark morph R. nasutus specimens were crossbred with standard (typically patterned) R. nasutus. RESULTS: We present the first occurrence of the melanic morphotype in the genus Rhodnius. The crossbreeding results demonstrate that the inheritance pattern of this characteristic follows Mendel's simple laws of segregation and an independent assortment of alleles. CONCLUSIONS: Phenotypic variation of R. nasutus reinforces the heterogeneity found in the Triatominae. Descriptions of new species in this subfamily require rigorous validation criteria.
Assuntos
Padrões de Herança/genética , Melaninas/genética , Pigmentação/genética , Rhodnius/genética , Animais , Feminino , Masculino , Fenótipo , Rhodnius/anatomia & histologia , Rhodnius/classificaçãoRESUMO
Aedes aegypti, a mosquito closely associated with humans, is the principal vector of dengue virus which currently infects about 400 million people worldwide. Because there is no way to prevent infection, public health policies focus on vector control; but insecticide-resistance threatens them. However, most insecticide-resistant mosquito populations exhibit fitness costs in absence of insecticides, although these costs vary. Research on components of fitness that vary with insecticide-resistance can help to develop policies for effective integrated management and control. We investigated the relationships in wing size, wing shape, and natural resistance levels to lambda-cyhalothrin of nine field isolates. Also we chose one of these isolates to select in lab for resistance to the insecticide. The main life-traits parameters were assessed to investigate the possible fitness cost and its association with wing size and shape. We found that wing shape, more than wing size, was strongly correlated with resistance levels to lambda-cyhalothrin in field isolates, but founder effects of culture in the laboratory seem to change wing shape (and also wing size) more easily than artificial selection for resistance to that insecticide. Moreover, significant fitness costs were observed in response to insecticide-resistance as proved by the diminished fecundity and survival of females in the selected line and the reversion to susceptibility in 20 generations of the non-selected line. As a practical consequence, we think, mosquito control programs could benefit from this knowledge in implementing efficient strategies to prevent the evolution of resistance. In particular, the knowledge of reversion to susceptibility is important because it can help in planning better strategies of insecticide use to keep useful the few insecticide-molecules currently available.
Assuntos
Aedes/efeitos dos fármacos , Aedes/fisiologia , Resistência a Inseticidas/fisiologia , Inseticidas/farmacologia , Nitrilas/farmacologia , Piretrinas/farmacologia , Animais , Feminino , Fertilidade/efeitos dos fármacos , Controle de Mosquitos/métodosRESUMO
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.
Assuntos
Evolução Molecular , Variação Genética , Insetos Vetores/genética , Rhodnius/genética , Animais , Núcleo Celular/genética , América Central , Colômbia , Citocromos b/classificação , Citocromos b/genética , Análise Citogenética , DNA Mitocondrial/química , DNA Mitocondrial/genética , Feminino , Geografia , Haplótipos , Humanos , Insetos Vetores/classificação , Insetos Vetores/parasitologia , Masculino , Dados de Sequência Molecular , NADH Desidrogenase/classificação , NADH Desidrogenase/genética , Filogenia , RNA Ribossômico 28S/classificação , RNA Ribossômico 28S/genética , Rhodnius/anatomia & histologia , Rhodnius/classificação , Análise de Sequência de DNA , Tripanossomíase/transmissão , Asas de Animais/anatomia & histologia , Asas de Animais/metabolismoRESUMO
Triatoma dimidiata is currently the main vector of Chagas disease in Mexico, most Central American countries and several zones of Ecuador and Colombia. Although this species has been the subject of several recent phylogeographic studies, the relationship among different populations within the species remains unclear. To elucidate the population genetic structure of T. dimidiata in Colombia, we analyzed individuals from distinct geographical locations using the cytochrome c oxidase subunit 1 gene and 7 microsatellite loci. A clear genetic differentiation was observed among specimens from three Colombian eco-geographical regions: Inter Andean Valleys, Caribbean Plains and Sierra Nevada de Santa Marta mountain (SNSM). Additionally, evidence of genetic subdivision was found within the Caribbean Plains region as well as moderate gene flow between the populations from the Caribbean Plains and SNSM regions. The genetic differentiation found among Colombian populations correlates, albeit weakly, with an isolation-by-distance model (IBD). The genetic heterogeneity among Colombian populations correlates with the eco-epidemiological and morphological traits observed in this species across regions within the country. Such genetic and epidemiological diversity should be taken into consideration for the development of vector control strategies and entomological surveillance.
Assuntos
Doença de Chagas/transmissão , Complexo IV da Cadeia de Transporte de Elétrons/genética , Repetições de Microssatélites/genética , Triatoma/genética , Triatoma/parasitologia , Animais , Doença de Chagas/epidemiologia , Colômbia/epidemiologia , Fluxo Gênico , Variação Genética , Humanos , Insetos Vetores/classificação , Insetos Vetores/genética , Insetos Vetores/parasitologia , Triatoma/classificação , Trypanosoma cruzi/patogenicidadeRESUMO
Rhodnius barretti, a new triatomine species, is described based on adult specimens collected in rainforest environments within the Napo ecoregion of western Amazonia (Colombia and Ecuador). R. barretti resembles Rhodnius robustus s.l., but mitochondrial cytochrome b gene sequences reveal that it is a strongly divergent member of the "robustus lineage", i.e., basal to the clade encompassing Rhodnius nasutus, Rhodnius neglectus, Rhodnius prolixus and five members of the R. robustus species complex. Morphometric analyses also reveal consistent divergence from R. robustus s.l., including head and, as previously shown, wing shape and the length ratios of some anatomical structures. R. barretti occurs, often at high densities, in Attalea butyracea and Oenocarpus bataua palms. It is strikingly aggressive and adults may invade houses flying from peridomestic palms. R. barretti must therefore be regarded as a potential Trypanosoma cruzi vector in the Napo ecoregion, where Chagas disease is endemic.
Assuntos
Doença de Chagas/transmissão , Doenças Endêmicas , Floresta Úmida , Rhodnius/anatomia & histologia , Rhodnius/classificação , Animais , Arecaceae , Teorema de Bayes , Doença de Chagas/epidemiologia , Colômbia , Citocromos b/genética , Ecologia , Ecossistema , Equador , Filogenia , Análise de Sequência , Especificidade da Espécie , Triatominae/classificaçãoRESUMO
Rhodnius barretti , a new triatomine species, is described based on adult specimens collected in rainforest environments within the Napo ecoregion of western Amazonia (Colombia and Ecuador). R. barretti resembles Rhodnius robustus s.l. , but mitochondrial cytochrome b gene sequences reveal that it is a strongly divergent member of the “robustus lineage”, i.e., basal to the clade encompassing Rhodnius nasutus , Rhodnius neglectus , Rhodnius prolixus and five members of the R. robustus species complex. Morphometric analyses also reveal consistent divergence from R. robustus s.l. , including head and, as previously shown, wing shape and the length ratios of some anatomical structures. R. barretti occurs, often at high densities, in Attalea butyracea and Oenocarpus bataua palms. It is strikingly aggressive and adults may invade houses flying from peridomestic palms. R. barretti must therefore be regarded as a potential Trypanosoma cruzi vector in the Napo ecoregion, where Chagas disease is endemic.
Assuntos
Animais , Doença de Chagas/transmissão , Doenças Endêmicas , Floresta Úmida , Rhodnius/anatomia & histologia , Rhodnius/classificação , Arecaceae , Teorema de Bayes , Colômbia , Doença de Chagas/epidemiologia , Citocromos b/genética , Ecologia , Ecossistema , Equador , Filogenia , Análise de Sequência , Especificidade da Espécie , Triatominae/classificaçãoRESUMO
Counts of immature stages of the mosquito Aedes aegypti have been used to calculate several entomological indices of dengue vector abundance. Some studies have concluded that these indices can be used as indicators of dengue epidemic risk, while other studies have failed to find a predictive relationship. Ecological niche models have been able to predict distributional patterns in space and time, not only of vectors, but also of the diseases that they transmit. In this study, we used Landsat 7 ETM+ images and two niche-modeling algorithms to estimate the local-landscape ecological niche and the dynamics of Ae. aegypti larval habitats in Bello, Colombia, and to evaluate their potential spatial and temporal distribution. Our models showed low omission error with high confidence levels: about 13.4% of the area presents conditions consistently suitable for breeding across the entire study period (2002-2008). The proportion of neighborhoods predicted to be suitable showed a positive association with dengue case rates, whereas the vector-focused Bretau index had no relationship to case rates. As a consequence, niche models appear to offer a superior option for predictive evaluation of dengue transmission risk and anticipating the potential for outbreaks.