MORPHOMETRIC DISTINCTION OF DOMESTIC AND SYLVATIC POPULATIONS OF Rhodnius ecuadoriensis FROM DIFFERENT GEOGRAPHICAL ORIGINS

ABSTRACTRhodnius ecuadoriensis (Hemiptera, Reduviidae) is an important vector of both Trypanosoma hemoflagellates, Trypanosoma cruzi and Trypanosoma rangeli, in Ecuador and Peru. Ecotopes of sylvatic and domestic/peridomestic habitats have been reported in Ecuador. Meanwhile in Peru, to the best of our knowledge, findings of sylvatic populations in their different ecosystem regions have not yet been documented. Could this be the product of a lack of appropriate studies on wild populations of triatominae in Peruvian environments? In order to elucidate this topic, we take advantage of new insights in geometric morphometry as a tool to help differentiate between wild populations and the corresponding domestic/peridomestic ones, collected in their respective environments. When analyzing our results, we confirmed the efficacy of this technique in our study, and furthermore, we believe that it could be a proper tool for rangeliosis and Chagas disease vector control surveillance in Ecuador and Peru.Keywords: Morphometric geometry, sylvatic, domestic/peridomiestic populations distinction, Rhodnius ecuadoriensis. RESUMENRhodnius ecuadoriensis (Hemiptera, Reduviidae) es un importante vector de los tripanosomas Trypanosoma cruzi y Trypanosoma rangeli en el Ecuador y Perú. Se han reportado ecotopos de hábitats silvestres y domésticos/peridomésticos en Ecuador. Sin embargo, en Perú, hasta donde sabemos, no se ha documentado hallazgos de dichas poblaciones silvestres. ¿Podría este ser el caso de una falta de estudios focalizados en la búsqueda de poblaciones silvestres de triatominos dentro de los diferentes ecosistemas del Perú? Para elucidar este tema, aplicamos nuevas perspectivas en morfometría geométrica, como una herramienta que podría auxiliar en la diferenciación de poblaciones silvestres de aquellas domésticas/peridomésticas, colectadas en sus respectivos ambientes naturales. Al analizar nuestros resultados, se confirmó la utilidad de esta técnica dentro de nuestro estudio, y esto nos llevó a creer asimismo que serviría como un elemento apropiado en el control vectorial de la enfermedad de Chagas y de la rangeliosis, en Ecuador y Perú.Palabras claves: Geometría morfométrica, silvestre, diferenciación de poblaciones domesticas/peridomesticas, Rhodnius ecuadoriensis

Nuclear rDNA ITS-2 sequences reveal polyphyly of Panstrongylus species (Hemiptera: Reduviidae: Triatominae), vectors of Trypanosoma cruzi.

Panstrongylus species are widely distributed throughout the Americas, where they act as vectors of Trypanosoma cruzi, agent of Chagas disease. Their intraspecific relationships, taxonomic position and phylogeny in relation to other Triatomini were explored using ribosomal DNA (rDNA) internal transcribed spacer 2 (ITS-2) sequence polymorphisms and maximum parsimony, distance and maximum likelihood analyses of 10 populations representing six species of the genus (P. megistus, P. geniculatus, P. rufotuberculatus, P. lignarius, P. herreri and P. chinai). At the subspecific level, P. megistus appeared more homogeneous than P. rufotuberculatus and P. geniculatus (both with broader distribution). Several dinucleotide microsatellites were detected in the sequences of given species. Many of these microsatellites (GC, TA, GT and AT) showed different number of repeats in different populations and thus, may be very useful for population differentiation and dynamics analyses in future studies. The sequences of P. lignarius (considered sylvatic) and P. herreri (a major disease vector in Peru) were identical, suggesting that these species should be synonymised. Intrageneric analysis showed a clear separation of P. rufotuberculatus, with closest relationships between P. geniculatus and P. chinai, and P. megistus occupying a separate branch. Genetic distances between Panstrongylus species (0.11585-0.22131) were higher than those between Panstrongylus and other Triatomini (16 species from central and North America and South America) (0.08617-0.11039). The distance between P. megistus and P. lignarius/herreri (0.22131) was the largest so far recorded in the tribe. The pronounced differences in length and nucleotide composition suggest a relatively old divergence of Panstrongylus species. P. rufotuberculatus was closer to Mesoamerican Triatoma, Meccus and Dipetalogaster species than to other Panstrongylus. All Panstrongylus clustered with the Mesoamerican clade; P. rufotuberculatus clustered with the phyllosoma complex and T. dimidiata, with D. maxima and T. barberi in a basal position. The rest of Panstrongylus appeared paraphyletically in the tree. This is evidence suggesting polyphyly within the genus Panstrongylus, whose species may be related to the ancestors giving rise to central and North American Triatomini

Limitations of selective deltamethrin application for triatomine control in central coastal Ecuador

<p>Abstract</p> <p>Background</p> <p>This year-long study evaluated the effectiveness of a strategy involving selective deltamethrin spraying and community education for control of Chagas disease vectors in domestic units located in rural communities of coastal Ecuador.</p> <p>Results</p> <p>Surveys for triatomines revealed peridomestic infestation with <it>Rhodnius ecuadoriensis </it>and <it>Panstrongylus howardi</it>, with infestation indices remaining high during the study (13%, 17%, and 10%, at initial, 6-month, and 12-month visits, respectively), which indicates a limitation of this strategy for triatomine population control. Infestation was found 6 and 12 months after spraying with deltamethrin. In addition, a large number of previously vector-free domestic units also were found infested at the 6- and 12-month surveys, which indicates new infestations by sylvatic triatomines. The predominance of young nymphs and adults suggests new infestation events, likely from sylvatic foci. In addition, infection with <it>Trypanosoma cruzi </it>was found in 65%, 21% and 29% at initial, 6-month and 12-month visits, respectively. All parasites isolated (n = 20) were identified as TcI.</p> <p>Conclusion</p> <p>New vector control strategies need to be devised and evaluated for reduction of <it>T. cruzi </it>transmission in this region.</p

Biogeography of Triatominae (Hemiptera: Reduviidae) in Ecuador: implications for the design of control strategies.

Chagas disease control strategies strongly depend on the triatomine vector species involved in Trypanosoma cruzi transmission within each area. Here we report the results of the identification of specimens belonging to various species of Triatominae captured in Ecuador (15 species from 17 provinces) and deposited in the entomological collections of the Catholic University of Ecuador (Quito), Instituto Oswaldo Cruz (Brazil), the Natural History Museum London (UK), the London School of Hygiene and Tropical Medicine (UK), the National Institute of Hygiene (Quito), and the Vozandes Hospital (Quito). A critical review of published information and new field records are presented. We analysed these data in relation to the life zones where triatomines occur (11 life zones, excluding those over 2,200 m altitude), and provide biogeographical maps for each species. These records are discussed in terms of epidemiological significance and design of control strategies. Findings relevant to the control of the main vector species are emphasised. Different lines of evidence suggest that Triatoma dimidiata is not native to Ecuador-Peru, and that synanthropic populations of Rhodnius ecuadoriensis in southern Ecuador-northern Peru might be isolated from their sylvatic conspecifics. Local eradication of T. dimidiata and these R. ecuadoriensis populations might therefore be attainable. However, the presence of a wide variety of native species indicates the necessity for a strong longitudinal surveillance system

Modeling Disease Vector Occurrence when Detection Is Imperfect: Infestation of Amazonian Palm Trees by Triatomine Bugs at Three Spatial Scales

Blood-sucking bugs of the genus Rhodnius are major vectors of Chagas disease. Control and surveillance of Chagas disease transmission critically depend on ascertaining whether households and nearby ecotopes (such as palm trees) are infested by these vectors. However, no bug detection technique works perfectly. Because more sensitive methods are more costly, vector searches face a trade-off between technical prowess and sample size. We compromise by using relatively inexpensive sampling techniques that can be applied multiple times to a large number of palms. With these replicated results, we estimate the probability of failing to detect bugs in a palm that is actually infested. We incorporate this information into our analyses to derive an unbiased estimate of palm infestation, and find it to be about 50% – twice the observed proportion of infested palms. We are then able to model the effects of regional, landscape, and local environmental variables on palm infestation. Individual palm attributes contribute overwhelmingly more than landscape or regional covariates to explaining infestation, suggesting that palm tree management can help mitigate risk locally. Our results illustrate how explicitly accounting for vector, pathogen, or host detection failures can substantially improve epidemiological parameter estimation when perfect detection techniques are unavailable