Trypanosomatid infections among vertebrates of Chile: a systematic review

We present a review on the natural infection by trypanosomatids of nonhuman vertebrates in Chile, aiming to synthesize and update the knowledge on the diversity of trypanosomatids infecting native and alien vertebrate species. To this end, we conducted a systematic review of literature records published from 1900 to April 2020 on four databases, focusing on the 21 genera of trypanosomatids and Chile. The methods and findings of our review have been based on the preferred reporting items for systematic reviews and meta-analysis (prisma) checklist. We found 29,756 records but only 71 presented relevant information for this review. Overall, there are only two reported trypanosomatid genera infecting vertebrate species in Chile, the genera Trypanosoma and Leishmania. The former is mostly represented by Trypanosoma cruzi (90% of the total records) and to a much lesser extent by Trypanosoma avium, Trypanosoma humboldti, Trypanosoma lewisi, and a couple of unidentified trypanosomatids. A total of 25 mammals have been reported as being infected by T. cruzi, including 14 native and 11 alien species from Orders Artiodactyla, Carnivora, Chiroptera, Didelphimorphia, Lagomorpha, Perissodactyla, and Rodentia. Extensive screening studies using new analytical tools are necessary to grasp the whole potential diversity of trypanosomatid species infecting vertebrates in Chile

Potential impact of climate change on the geographical distribution of two wild vectors of Chagas disease in Chile: Mepraia spinolai and Mepraia gajardoi

Background: Mepraia gajardoi and Mepraia spinolai are endemic triatomine vector species of Trypanosoma cruzi, a parasite that causes Chagas disease. These vectors inhabit arid, semiarid and Mediterranean areas of Chile. Mepraia gajardoi occurs from 18° to 25°S, and M. spinolai from 26° to 34°S. Even though both species are involved in T. cruzi transmission in the Pacific side of the Southern Cone of South America, no study has modelled their distributions at a regional scale. Therefore, the aim of this study is to estimate the potential geographical distribution of M. spinolai and M. gajardoi under current and future climate scenarios. Methods: We used the Maxent algorithm to model the ecological niche of M. spinolai and M. gajardoi, estimating their potential distributions from current climate information and projecting their distributions to future climatic conditions under representative concentration pathways (RCP) 2.6, 4.5, 6.0 and 8.5 scenarios. Future predictions of suitability were constructed considering both higher and lower public health risk situations. Results: The current potential distributions of both species were broader than their known ranges. For both species, climate change projections for 2070 in RCP 2.6, 4.5, 6.0 and 8.5 scenarios showed different results depending on the methodology used. The higher risk situation showed new suitable areas, but the lower risk situation modelled a net reduction in the future potential distribution areas of M. spinolai and M. gajardoi. Conclusions: The suitable areas for both species may be greater than currently known, generating new challenges in terms of vector control and prevention. Under future climate conditions, these species could modify their potential geographical range. Preventive measures to avoid accidental human vectorial transmission by wild vectors of T. cruzi become critical considering the uncertainty of future suitable areas projected in this study.Fil: Garrido Sanchis, Rubén. Universidad de Chile; Chile. Universidad Católica del Maule; ChileFil: Bacigalupo, Antonella. Universidad de Chile; ChileFil: Peña Gómez, Francisco. Universidad de Chile; ChileFil: Bustamante, Ramiro O.. Universidad de Chile; ChileFil: Cattan, Pedro E.. Universidad de Chile; ChileFil: Gorla, David Eladio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Diversidad y Ecología Animal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto de Diversidad y Ecología Animal; ArgentinaFil: Botto Mahan, Carezza. Universidad de Chile; Chil

Allogeneic Stem Cell Transplantation Compared with Chemotherapy for Poor-Risk Hodgkin Lymphoma

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Population genomics and geographic dispersal in Chagas disease vectors: landscape drivers and evidence of possible adaptation to the domestic setting

Accurate prediction of vectors dispersal, as well as identification of adaptations that allow blood-feeding vectors to thrive in built environments, are a basis for effective disease control. Here we adopted a landscape genomics approach to assay gene flow, possible local adaptation, and drivers of population structure in Rhodnius ecuadoriensis, an important vector of Chagas disease. We used a reduced-representation sequencing technique (2b-RADseq) to obtain 2,552 SNP markers across 272 R. ecuadoriensis samples from 25 collection sites in southern Ecuador. Evidence of high and directional gene flow between seven wild and domestic population pairs across our study site indicates insecticide-based control will be hindered by repeated re-infestation of houses from the forest. Preliminary genome scans across multiple population pairs revealed shared outlier loci potentially consistent with local adaptation to the domestic setting, which we mapped to genes involved with embryogenesis and saliva production. Landscape genomic models showed elevation is a key barrier to R. ecuadoriensis dispersal. Together our results shed early light on the genomic adaptation in triatomine vectors and facilitate vector control by predicting that spatially-targeted, proactive interventions would be more efficacious than current, reactive approaches

Modelo predictivo de la distribución de triatominos a escala local

Memoria para optar al Título Profesional de Médico Veterinario. Tesis para optar al Grado de Magíster en Ciencias Animales y Veterinarias mención Medicina Preventiva Animal.El objetivo de este estudio fue determinar un modelo predictivo de distribución de focos de triatominos a escala local en zonas rurales del área endémica de Chile. Se realizó un muestreo sistemático por conglomerados en 3 zonas de estudio: Aucó, en la Región de Coquimbo; Putaendo, en la Región de Valparaíso; y Til-Til, en la Región Metropolitana, utilizando trampas de levadura en fermentación y observación directa para realizar un recuento de triatominos en cada punto investigado. Se determinó el patrón de distribución de los triatominos mediante el índice de autocorrelación de Moran. Mediante variables medidas en terreno y variables calculadas desde productos de sensores remotos, se determinaron aquellas que resultaron diferentes entre sitios con y sin triatominos, utilizando el test de Kruskal-Wallis. Con las variables derivadas de sensores remotos se generaron modelos predictivos de la distribución de los triatominos mediante el software Maxent, los que se proyectaron en 3 zonas donde no se había realizado el muestreo sistemático. Se compararon los modelos generados al utilizar una resolución espacial de 6x6 metros respecto a una resolución de 1x1 metro, y además se comparó el incorporar el total de las variables al modelo respecto a utilizar sólo aquellas que resultaron significativas previamente. Para la validación de los modelos se utilizó el software Partial ROC para la predicción umbral independiente, y la probabilidad de la distribución binomial en el caso de la predicción binaria al aplicar un umbral, utilizando puntos positivos a triatominos que no habían sido ocupados en la modelación. El recuento de triatominos fue 211, todos de la especie Mepraia spinolai. La distribución espacial de las capturas tuvo un patrón agrupado a nivel de puntos investigados, pero fue aleatoria al analizarlo entre conglomerados. Las variables de terreno que fueron significativamente diferentes entre puntos con y sin triatominos detectados fueron: la pendiente, el porcentaje de piedras, de vegetación herbácea y de vegetación arbustiva, y el promedio de humedad relativa. Las variables producto de sensores remotos que se diferenciaban según la presencia de triatominos fueron: la pendiente, la exposición, el índice de vegetación NDVI y la distancia a construcciones. Los resultados de los modelos predictivos de distribución de M. spinolai indicaron que el modelo de resolución espacial 6x6 m con 6 variables (aquellas significativas más la altitud y la distancia a cursos de agua) tuvo el mayor ajuste, por lo que podría utilizarse este modelo para determinar áreas con riesgo elevado de presencia de vectores de la enfermedad de Chagas a escala local en ChileThe goal of this study was to determine a predictive distribution model of triatomines’ foci at local scale in rural areas of the endemic area of Chile. Systematic sampling by clusters was carried out in three study areas: Aucó, in the Region of Coquimbo; Putaendo, in the Region of Valparaiso; and Til-Til, in the Metropolitan Region, using yeast baited traps and direct observation to count triatomines at each assessed point. The distribution pattern of the triatomines was determined using the Moran autocorrelation index. Field variables and variables calculated from remote sensing products were compared between sites with and without triatomines using the Kruskal-Wallis test. Predictive models of the distribution of the triatomines were generated with the variables derived from remote sensors, using Maxent software. These models were projected in 3 areas where systematic sampling was not performed. The models generated were compared using a spatial resolution of 6x6 meters and of 1x1 meter, and comparing the incorporation of the total of the variables to the model or using only those previously significant. Model validation was performed using Partial ROC software for the thresholdindependent prediction, and using the binomial distribution probability for the binary prediction, when applying a threshold; triatomine positive points that had not been used previously for modeling were used for validation. The triatomines’ count was 211, all from the species Mepraia spinolai. The spatial distribution of the triatomines had a clustered pattern at the point level, but it was random when analyzed between clusters. The field variables that were significantly different between points with and without triatomines were: slope, percentage of stones, herbaceous vegetation and shrub vegetation, and average relative humidity. The variables from remote sensors that differed according to the presence of triatomines were: slope, aspect, NDVI vegetation index and distance to constructions. The predictive distribution models of M. spinolai results indicated that the model of spatial resolution 6x6 m with 6 variables (those significant plus elevation and distance to watercourses) had higher accuracy, so it could be used to determine areas with an elevated risk of Chagas disease vectors’ presence at a local scale in ChileFinanciamiento: Proyecto Fondecyt No. 1100339 y No. 1140650

Zika: probability of establishment of its vector, Aedes aegypti, in Chile

The Zika virus has raised world alarm in recent years, representing a major public health problem. In this study we evaluated the potential risk of exposure to Zika virus in Chile, associated with the probability of establishment of the vector Aedes aegypti in the country. Niche modelling techniques were used to project the bioclimatic requirements of the vector (global niches), identifying zones of high suitability for the species within the country. Then, the potential distribution of the vector in Chile was overlapped with the human population density, estimating the risk associated to the potential co-occurrence of both in a spatially explicit manner. We identified bioclimatic suitability for A. aegypti in continental Chile, from the northern tropical area to temperate regions, mainly in coastal zones. The exposed population could reach 1.8 million people, with 1.3 million in a medium level of potential risk and 21,000 in a high level. These results support that there is a significant probability of success for the Zika virus main vector to colonize continental Chile in case of an introduction. Therefore, prevention, monitoring, and control play an important role in avoiding the arrival of this vector to our country.El virus Zika ha despertado una alarma mundial en los últimos años, representando un problema importante para la salud pública. En este estudio evaluamos el riesgo potencial de exposición a virus Zika en Chile, asociado a la probabilidad de establecimiento del vector Aedes aegypti en el país. Se utilizaron técnicas de modelación de nicho para proyectar los requerimientos bioclimáticos del vector (nicho global), identificando las zonas de alta idoneidad para la especie en el país. Luego, se superpuso la distribución potencial del vector en Chile con la densidad de población humana, estimando en forma espacialmente explícita el riesgo asociado a la co-ocurrencia potencial de ambos. Identificamos que existe idoneidad bioclimática para A. aegypti en Chile continental, desde el área tropical del norte hasta regiones templadas, principalmente en zonas costeras. La población potencialmente expuesta podría alcanzar 1,8 millones de personas, con 1,3 millones en nivel medio y 21.000 en niveles altos de riesgo potencial de exposición. Los resultados expuestos aquí muestran que existe una significativa probabilidad de éxito de colonización del vector principal de virus Zika en Chile continental en caso de una introducción. Por lo tanto, la prevención, monitoreo y control se vuelven un tema importante para evitar la llegada de este vector a Chile continental