BackgroundKnockdown resistance (kdr), caused by alterations in the voltage-gated sodium channel (NaV), is one of the mechanisms responsible for pyrethroid (PY) resistance. In the Asian tiger mosquito, Aedes albopictus, at least four different mutations were described in the IIIS6 NaV segment in populations from Asia, North America and Europe. In contrast, in Aedes aegypti at least 12 non-synonymous mutations have been reported at nine different codons, mostly in the IIS6 and IIIS6 NaV segments. The Phe1534Cys kdr mutation in the IIIS6 NaV segment is the most prevalent in populations of Ae. aegypti worldwide, also found in Ae. albopictus from Singapore. Herein, we investigated the DNA diversity corresponding to the IIS6 and IIIS6 NaV segments in natural populations of Ae. albopictus from Brazil.MethodsDNA from eight Brazilian Ae. albopictus natural populations were individually extracted and pooled by states of origin, amplified, cloned and sequenced for the corresponding IIS6 and IIIS6 NaV segments. Additionally, samples from each location were individually genotyped by an allelic specific PCR (AS-PCR) approach to obtain the genotypic and allelic frequencies for the 1534 NaV site.ResultsNo non-synonymous substitutions were observed in the IIS6 sequences. However, the Phe1534Cys kdr mutation was evidenced in the Ae. albopictus NaV IIIS6 segment sequences from Paraná (PR) and Rondônia (RO) states, but not from Mato Grosso (MT) state. The 1534Cyskdr allele varied from 3% (Marilena/PR and Porto Velho/RO) to 10% (Foz do Iguaçu/PR). To our knowledge, this paper reports the first occurrence and provides distribution data of a possible kdr mutation in Ae. albopictus in South America.ConclusionThe emergence of a likely kdr mutation in Ae. albopitus natural populations is a signal of alert for vector control measures since PY are the most popular insecticides adopted by residents. Additionally, once the kdr allele is present, its frequency tends to increase faster under exposition to those compounds. Although the Asian tiger mosquito is not incriminated as an important vector of dengue, chikungunya and Zika viruses in South America, its importance in this regard has been extensively discussed since Ae. albopictus is rapidly spreading and can also migrate between sylvatic and urban environments. Therefore, insecticide resistance monitoring initiatives should also be extended to Ae. albopictus in Brazil in order to maintain chemical compounds as an efficient vector control tool when needed.Electronic supplementary materialThe online version of this article (doi:10.1186/s13071-017-2089-5) contains supplementary material, which is available to authorized users.
In Colombia, little is known on the distribution of the Asian mosquito Aedes albopictus, main vector of dengue, chikungunya, and Zika in Asia and Oceania. Therefore, this work sought to estimate its current and future potential geographic distribution under the Representative Concentration Paths (RCP) 2.6 and 8.5 emission scenarios by 2050 and 2070, using ecological niche models. For this, predictions were made in MaxEnt, employing occurrences of A. albopictus from their native area and South America and bioclimatic variables of these places. We found that, from their invasion of Colombia to the most recent years, A. albopictus is present in 47% of the country, in peri-urban (20%), rural (23%), and urban (57%) areas between 0 and 1800 m, with Antioquia and Valle del Cauca being the departments with most of the records. Our ecological niche modelling for the currently suggests that A. albopictus is distributed in 96% of the Colombian continental surface up to 3000 m (p < 0.001) putting at risk at least 48 million of people that could be infected by the arboviruses that this species transmits. Additionally, by 2050 and 2070, under RCP 2.6 scenario, its distribution could cover to nearly 90% of continental extension up to 3100 m (≈55 million of people at risk), while under RCP 8.5 scenario, it could decrease below 60% of continental extension, but expand upward to 3200 m (< 38 million of people at risk). These results suggest that, currently in Colombia, A. albopictus is found throughout the country and climate change could diminish eventually its area of distribution, but increase its altitudinal range. In Colombia, surveillance and vector control programs must focus their attention on this vector to avoid complications in the national public health setting.
RESUMENSe realizó un estudio con el fin de determinar la estructura demográfica de Emilia sonchifolia (L.) DC en una finca cafetera del Municipio de Armenia, Quindío, Colombia, donde se recolectaron datos durante cuatro semanas, en tres sitios: exterior, borde e interior del cultivo. Usando parámetros calculados a partir de los datos de campo, se construyó un modelo logístico para describir el comportamiento poblacional de E. sonchifolia en el tiempo. Se encontraron diferencias significativas en las variables: número de individuos por estado etario en el tiempo, porcentaje de mortalidad, tiempo de cambio del estado plántula a juvenil y de juvenil a adulto, número de hojas y de ramas; no se encontraron diferencias significativas en la densidad poblacional, número de inflorescencias e infrutescencias en los sitios de estudio. En general, se puede atribuir este comportamiento a la estrategia de reproducción r que sigue E. sonchifolia. Finalmente, las simulaciones hechas a partir del modelo logístico sugieren que la especie tiende a desaparecer si alguno de los estados etarios no está presente inicialmente; así, una alternativa plausible para el control sería su eliminación en el estado juvenil. Los resultados ofrecen alternativas con respecto al manejo de poblaciones de arvenses.Palabras clave: café, demografía, maleza, modelo. ABSTRACTA research study was conducted to determine the demographic structure of Emilia sonchifolia L. in a coffee plantation in Armenia, Quindío, Colombia. Data were collected over a period of four weeks on three sites: inside, at the border and outside a coffee farm. A logistic population model was built to describe the population behavior of E. sonchifolia over time. Statiscally significant differences were found between: number of individuals per life stage in time, mortality rate, transition time from seedling to juvenile and from juvenile to adult; and number of leaves and branches. There was no evidence for statistically significant differences in population density or in number of inflorescences and fruits between study sites. In general, the observed behavior may be attributed to the r strategy used by this species. Finally, our results suggest the survival of the species is conditioned by the presence of all life stages at the beginning of each simulation based on the logistic model; so, a potential strategy for its controlling would require the removal during the juvenile stage. The considerations offer alternatives regarding weed population management.
Background Mayaro virus (Togaviridae) is an endemic arbovirus of the Americas with epidemiological similarities with the agents of other more prominent diseases such as dengue (Flaviviridae), Zika (Flaviviridae), and chikungunya (Togaviridae). It is naturally transmitted in a sylvatic/rural cycle by Haemagogus spp., but, potentially, it could be incorporated and transmitted in an urban cycle by Aedes aegypti, a vector widely disseminated in the Americas. Methods The Mayaro arbovirus dynamics was simulated mathematically in the colombian population in the eight biogeographical provinces, bearing in mind the vector’s population movement between provinces through passive transport via truck cargo. The parameters involved in the virus epidemiological dynamics, as well as the vital rates of Ae. aegypti in each of the biogeographical provinces were obtained from the literature. These data were included in a meta-population model in differential equations, represented by a model structured by age for the dynamic population of Ae. aegypti combined with an epidemiological SEI/SEIR-type model. In addition, the model was incorporated with a term of migration to represent the connectivity between the biogeographical provinces. Results The vital rates and the development cycle of Ae. aegypti varied between provinces, having greater biological potential between 23 °C and 28 °C in provinces of Imerí, biogeographical Chocó, and Magdalena, with respect to the North-Andean Moorland (9.33–21.38 °C). Magdalena and Maracaibo had the highest flow of land cargo. The results of the simulations indicate that Magdalena, Imerí, and biogeographical Chocó would be the most affected regarding the number of cases of people infected by Mayaro virus over time. Conclusions The temperature in each of the provinces influences the local population dynamics of Ae. aegypti and passive migration via transport of land cargo plays an important role on how the Mayaro virus would be disseminated in the human population. Once this arbovirus begins an urban cycle, the most-affected departments would be Antioquia, Santander, Norte de Santander, Cesar (Provinces of Magdalena), and Valle del Cauca, and Chocó (biogeographical province of Chocó), which is why vector control programmes must aim their efforts at these departments and include some type of vector control to the transport of land cargo to avoid a future Mayaro epidemic.
ResumenEl dengue, chikunguña y Zika, todas transmitidas por Aedes aegypti, son enfermedades que afectan ampliamente la población mundial. La evaluación de extractos vegetales permite el establecimiento de productos efi cientes para el control de éste mosquito. Este trabajo evaluó la actividad larvicida en A. aegypti de 23 especies de la familia Asteraceae, y su composición fi toquímica preliminar. El material vegetal utilizado se recolectó en el Departamento del Quindío, Colombia. Con este material se prepararon los extractos vegetales etanólicos utilizados en la caracterización fi toquímica y en los bioensayos. Para cada extracto se realizó un bioensayo dosis-respuesta con larvas provenientes del municipio de Armenia (Quindío, Colombia) siguiendo el protocolo de la OMS. Estos indican que, después de 48 h, los extractos de Jaegeria hirta (694,8% ± 149,9), Austroeupatorium inulaefolium (753,3% ± 198,8) y Heliopsis oppsitifolia (764,4% ± 170,0) requieren menor concentración para matar el 95% de las larvas. Adicionalmente, se construyó un modelo matemático que describe el comportamiento de las poblaciones, con el fi n de evaluar diferentes estrategias de control con los extractos; las simulaciones obtenidas a partir de la solución numérica del sistema permiten concluir que la aplicación de extractos de estas plantas constituye una herramienta viable para el control de A. aegypti. Por su parte, la marcha fi toquímica preliminar de las 23 especies muestra la presencia de taninos, quinonas, fl avonoides, esteroles, cumarinas y alcaloides. Se concluye que J. hirta, A. inulaefoliu y H. oppsitifolia ameritan ser estudiadas en profundidad, dado su potencial larvicida para el control de A. aegypti. AbstractDengue, chikungunya and Zika, all transmitted by Aedes aegypti, are diseases that affect the human world population. The evaluation of raw plant extracts allows the establishment of effi cient products for the control of populations of this mosquito. This work evaluated the larvicidal activity of 23 species of the family Asteraceae, and its preliminary phytochemical composition, to control populations of A. aegypti. The vegetable material was collected in the department of Quindío, Colombia. We prepared the plant extracts used in the phytochemical characterization and bioassays with the material collected. For each extract, a dose-response bioassay was performed with larvae from the municipality of Armenia (Quindío, Colombia) following the WHO protocol. These assays indicated that after 48h the extracts of Jaegeria hirta (694.8% ± 149.9), Austroeupatorium inulaefolium (753. 3% ± 198.8) and Heliopsis oppsitifolia (764.4% ± 170.0) require less concentration to kill 95% of larvae. Additionally, a mathematical model that describes the behavior of the mosquito populations was constructed, in order to evaluate different control strategies using the extracts; the simulations obtained from the numerical solution of the system allow us to conclude that the application of extracts from these plants constitutes a viable tool for A...
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