Abstract:

Mosquitoes in artificial containers include Aedes aegypti and the Culex pipiens complex, both recognized worldwide as vectors of diseases. The goal of this study was to characterize mosquito communities in water-filled artificial containers in the islands of one of the major temperate wetlands in South America, and to assess whether A. aegypti is present in the area. Five domestic areas located in the insular Tigre District (Buenos Aires Province, Argentina) were visited monthly between November 2011 and May 2012. A total of 1013 artificial containers (half of them with water) were inspected for mosquito immatures. 3359 specimens corresponding to seven species were collected in 88 containers. A. aegypti was recorded for the first time in this wetland, and in all land use categories examined from February to May. Among the remaining six species, only Culex dolosus and C. pipiens were highly abundant. 88% of the mosquito positive containers were buckets, dustbins and boats, whereas highly available bottles did not act as mosquito breeding habitats; the key breeding container was different for each land use. The Container Index showed differences among land uses, materials, water capacity and volume, and insolation levels. Generalized Linear Mixed Models suggested that the probability of finding mosquitoes was higher for containers located in dumps and recreational areas, made of resin/fiberglass, presenting intermediate water volumes, and not in use if partially or totally shaded but in use for sunlit containers. Recommendations for mosquito prevention and control in the islands are proposed.

Author affiliation: Cardo, María Victoria. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de San Martín. Instituto de Investigaciones e Ingeniería Ambiental. Laboratorio de Ecología de Enfermedades Transmitidas por Vectores; Argentina

Author affiliation: Rosín, Paula. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina

Author affiliation: Carbajo, Anibal Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de San Martín. Instituto de Investigaciones e Ingeniería Ambiental. Laboratorio de Ecología de Enfermedades Transmitidas por Vectores; Argentina

Author affiliation: Vezzani, Dario. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina

Abstract:

Given their medical and veterinary relevance, the members of the Pipiens Assemblage are a worldwide target of ecological research. The distribution of Culex pipiens s.s. and Cx. quinquefasciatus converge in Buenos Aires, Argentina, where hybrids have been detected. Each member of the assemblage exhibits a distinct eco-physiological behaviour that can affect its efficiency in pathogen transmission. Our aim was to identify the environmental drivers for the spatio-temporal distribution of each member, focusing on latitudinal and urbanisation gradients. Immatures of mosquitoes were surveyed in artificial containers found within 11 public cemeteries, raised up to the adult stage and identified by their male genitalia. The distribution of each member was associated with the environment in a Generalized Linear Model. The variable accounting for most of the heterogeneity was latitude; Cx. quinquefasciatus was collected more frequently at northern cemeteries, whereas Cx. pipiens and hybrids were more likely at the southern extreme. The urbanisation gradient was also associated with the occurrence of Cx. quinquefasciatus and hybrids at the high and low end, respectively. Other relevant variables were cemetery total area, the proportion with graves and the presence of plastic flowers in the containers. The spatial distribution of the members of the Pipiens Assemblage within the sympatric region in South America is driven by environmental features. The information presented herein provides essential baseline data for surveillance programs and control activities.

Author affiliation: Cardo, María Victoria. Universidad Nacional de San Martín. Instituto de Investigaciones e Ingeniería Ambiental. Laboratorio de Ecología de Enfermedades Transmitidas por Vectores; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Author affiliation: Rubio, Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de San Martín. Instituto de Investigaciones e Ingeniería Ambiental. Laboratorio de Ecología de Enfermedades Transmitidas por Vectores; Argentina

Author affiliation: Junges, Melania Teresita. Universidad Nacional de San Martín. Instituto de Investigaciones e Ingeniería Ambiental. Laboratorio de Ecología de Enfermedades Transmitidas por Vectores; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Author affiliation: Vezzani, Dario. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Instituto Multidisciplinario de Ecosistemas y Desarrollo Sustentable; Argentina

Author affiliation: Carbajo, Anibal Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de San Martín. Instituto de Investigaciones e Ingeniería Ambiental. Laboratorio de Ecología de Enfermedades Transmitidas por Vectores; Argentina

Abstract:

Characterizing mosquito larval habitats is essential for understanding the complex interactions between immatures and the biotic and abiotic components of their environment. Using generalized linear mixed models, we studied the environmental predictors of the presence of three ubiquitous mosquito species breeding in ground water habitats in the Paraná Lower Delta, Argentina. During a year-round survey, 34.1% of the 419 ground water habitats inspected were positive for either Culex dolosus s.l. (Lynch Arribálzaga 1891), Aedes crinifer (Theobald 1903), or Culex intrincatus Brèthes 1916. Univariate analysis showed that the former two occurred throughout the year, whereas the latter during the summer and fall. Ae. crinifer and Cx. intrincatus were more frequently collected in secondary forests, whereas Cx. dolosus s.l. was homogeneously distributed among land uses. Best generalized linear mixed models included the sampling period and landscape variables in different combinations for each species. Spatial dependence of the data was evident for Cx. dolosus s.l. and Ae. crinifer. Our results showed that the most widespread species presented different spatio-temporal distribution patterns, related with land use, anthropic intervention, and seasonality, highlighting the complexity of the wetland under study. This methodological approach could aid in the selection of priority areas for vector control and disease risk management.

Author affiliation: Cardo, María Victoria. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución. Unidad de Ecología de Reservorios y Vectores de Parásitos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Author affiliation: Vezzani, Dario. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución. Unidad de Ecología de Reservorios y Vectores de Parásitos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Author affiliation: Carbajo, Anibal Eduardo. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución. Unidad de Ecología de Reservorios y Vectores de Parásitos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Abstract:

Los humedales son ecosistemas muy favorables para los insectos con estadios acuáticos, y dada su compleja dinámica del agua, son escenarios ideales para evaluar la influencia de las características ecofisiológicas de las especies en la estructuración de las comunidades en función del ambiente. En esta tesis, se investigó cómo se estructuran las comunidades de mosquitos (Diptera: Culicidae) que habitan en cuerpos de agua en el suelo (CAS) en función de la heterogeneidad ambiental a tres escalas espaciales de un humedal considerando sus efectos sobre distintas estrategias de oviposición. Entre los 1.689 CAS inspeccionados durante 2008- 2012 en el Bajo Delta del Río Paraná, se colectaron en total 10.626 inmaduros de mosquitos pertenecientes a 32 especies de siete géneros. Mediante el uso de modelos lineales generalizados y análisis de nicho se identificaron variaciones en la estructura de distintas comunidades en respuesta a la estacionalidad, a las características propias de los CAS, al uso de la tierra y al paisaje. Dichas respuestas dependieron de la estrategia de oviposición, siendo distintas las asociaciones entre la dinámica del agua (lluvia y mareas) y el uso de la tierra para mosquitos de inundación y de balsa. La composición del ensamble en CAS temporarios varió en función del paisaje, no así los otros atributos comunitarios; los patrones de recambio de especies estuvieron dominados por mosquitos de inundación. El conjunto de resultados sugiere que la heterogeneidad ambiental a distintas escalas espaciales afecta distintos atributos de las comunidades de mosquitos, y que las estrategias de oviposición tienen un rol central en dicha relación.

Wetlands are highly favorable ecosystems for insects with aquatic stages and, given their complex water dynamics, they are the ideal setting to assess the influence of ecophysiological characteristics of the species in the structuring of the communities as a function of the environment. In this thesis, the structuring of mosquito (Diptera: Culicidae) communities breeding in ground-water habitats (GWH) as a function of environmental heterogeneity in a wetland was evaluated, considering its effects at three spatial scales on different oviposition strategies. A total of 10,626 mosquito immatures of 32 species from seven genera were collected among 1,689 GWH inspected during 2008-2012 in the Paraná Lower Delta. Using generalized linear models and outlying mean index analysis, variations in the structure of different communities were identified in response to seasonality, the characteristics intrinsic to each GWH type, the landuse and the landscape. Such variations depended on the oviposition strategy, with floodwater and raft-laying mosquitoes showing distinct associations between water dynamics (precipitation and tidal regime) and landuse. In contrast to all other community attributes evaluated, the composition of the assemblage of temporary GWH varied as a function of the landscape, with floodwater mosquitoes dominating species replacement patterns. These results suggest that the environmental heterogeneity at different spatial scales affect different attributes of mosquito communities, and that oviposition strategies play a central role in this relation.

Author affiliation: Cardo, María Victoria. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.

Abstract:

Taosa longula Remes Lenicov (Hemiptera: Dictyopharidae), a planthopper native to South America, is a candidate for the biological control of water hyacinth, Eichhornia crassipes (Mart.) Solms-Laubach (Pontederiaceae), a serious weed worldwide. Biological control requires agents that are not only specific but also effective. Damage caused by sap-sucking insects is difficult to assess. In this work we designed an experimental and analytical procedure to evaluate the potential damage of T. longula on water hyacinth. The damage that T. longula causes to the clonal reproduction, biomass production, and growth of water hyacinth was studied through a paired greenhouse trial with floating cages. The performance of the plant, starting from two plants per treatment, was evaluated at different insect densities (5, 10, 15 and 20 nymphs per cage) until all the nymphs moulted to adults. The tests showed that individual growth and biomass production of water hyacinth was reduced due to the effect of the insect feeding above five nymphs per cage. The number of new plants produced by clonal reproduction was only significantly different above 15 nymphs per cage. These results suggest that this planthopper could be an effective agent for the biological control of water hyacinth.

Author affiliation: Sacco, Joaquín. Laboratorios Fox; Argentina

Author affiliation: Cabrera Walsh, Guillermo José. Fundación para el Estudio de Especies Invasivas; Argentina

Author affiliation: Hernández, M. Cristina. Fundación para el Estudio de Especies Invasivas; Argentina

Author affiliation: Sosa, Alejandro Joaquín. Fundación para el Estudio de Especies Invasivas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Author affiliation: Cardo, María Victoria. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Author affiliation: Elsesser, Gerardo. Universidad Maimónides; Argentina

Abstract:

The mosquitoes of the Culex pipiens complex, hereafter referred to as the Pipiens Assemblage, are vectors of arbovirus of worldwide concern including West Nile and St. Louis encephalitis. Given their distinct eco-physiology and vectorial capacity, accurate specimen identification and insight in the environmental drivers of their distribution are essential for the understanding of disease transmission patterns. Using a PCR-based identification protocol, we characterized the spatial distribution of Cx. pipiens, Cx. quinquefasciatus and their hybrids developing in used tyres located within the overlapping region in South America as a function of different estimators of the urbanisation gradient. Out of 84 samples collected from tyre piles of 20 sites, we identified 369 larvae which corresponded predominantly to Cx. quinquefasciatus (76.4% of immatures) all along the gradient but more frequent at the urban end. Cx. pipiens (21.4%) was more conspicuous at the low urbanised end but was also present in highly urbanised sites, whereas hybrids were collected in very low numbers (2.2%). The urbanisation estimator best associated with the heterogeneous occurrence of the Pipiens Assemblage members was the proportion of impervious surface 1 km around each tyre pile, which explained 41.7% of the variability in the data, followed closely by the distance to the Capital City (38.3%). Cumulative annual precipitation, population number in a 1 km radius around each pile and distance to the de la Plata River were significantly associated with the distribution of the Pipiens Assemblage at lower explanation percentages (20–23%). A thorough understanding of the ecological basis and environmental associations of the distribution of Pipiens Assemblage members will enable forecasting population trends in changing environments to develop effective control measures for mosquitoes and the diseases they transmit.

Author affiliation: Cardo, María Victoria. Universidad Nacional de San Martín. Instituto de Investigaciones e Ingeniería Ambiental. Laboratorio de Ecología de Enfermedades Transmitidas por Vectores; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Author affiliation: Rubio, Alejandra. Universidad Nacional de San Martín. Instituto de Investigaciones e Ingeniería Ambiental. Laboratorio de Ecología de Enfermedades Transmitidas por Vectores; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Author affiliation: Junges, Melania Teresita. Universidad Nacional de San Martín. Instituto de Investigaciones e Ingeniería Ambiental. Laboratorio de Ecología de Enfermedades Transmitidas por Vectores; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Author affiliation: Vezzani, Dario. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Instituto Multidisciplinario de Ecosistemas y Desarrollo Sustentable; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Author affiliation: Carbajo, Anibal Eduardo. Universidad Nacional de San Martín. Instituto de Investigaciones e Ingeniería Ambiental. Laboratorio de Ecología de Enfermedades Transmitidas por Vectores; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Abstract:

Dengue and Saint Louis encephalitis virus are among the mostimportant emerging viruses transmitted by mosquitoes at the global scale, and from 2009 onward both diseases have reached temperate Argentina. To test whether the urbanization level can be used as a predictor for the infestation levels of containerbreedingmosquito vectors, we searched for Aedes aegypti and Culex pipiens in 8400 water-filled containers from 14 cemeteries of Buenos Aires Province and we used generalized linear models to relate positive containers withthe impervious area quantified inside (internal PIA) and outside (external PIA) cemeteries. The bestmodelfor Ae. aegypti explained 91%ofthe variability and included the season,the internal PIAand the external PIA at 1 km as a quadratic function, showing a parabolic response peaking in ∼75%. Regarding the infestation levels of Cx. pipiens, the final model explained 75% of the variability and included only the season. In view of these results, the percentage of impervious area efficiently predicted the infestation levels of Ae. aegypti but not of Cx. pipiens. Considering the worldwide relevance of the former in dengue transmission, the simple quantification of imperviousness proposed herein provides a helpful basis for vector surveillance and control in urbanized areas.

Author affiliation: Rubio, Alejandra. Universidad Nacional de San Martín. Instituto de Investigación e Ingeniería Ambiental; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Author affiliation: Cardo, María Victoria. Universidad Nacional de San Martín. Instituto de Investigación e Ingeniería Ambiental; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Author affiliation: Carbajo, Anibal Eduardo. Universidad Nacional de San Martín. Instituto de Investigación e Ingeniería Ambiental; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Author affiliation: Vezzani, Dario. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución. Unidad de Ecología de Reservorios y Vectores de Parásitos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Abstract:

Cities are unique ecosystems emerging and growing worldwide due to ongoing urbanising trends. The urban–rural gradient is an excellent setting to evaluate the effect of urbanisation on the distribution of species, a matter of public health concern in the case of disease vectors. Despite this, such distributions are affected by other co-occurring variables, mainly meteorological, that may be confounded by the urbanisation gradient due to the urban heat island effect and maritime climatological conditions in the case of coastal cities. To aid in the design of ecological studies within the urban–rural transition zone, a mapping protocol was designed and applied to Buenos Aires City and its surroundings. Based on road density and district-level population counts, a detailed (1 km2 pixel) urbanisation map was obtained which, combined with a temperature map, rendered a final urbanisation × temperature product with six classes. The resulting zonation was tested by modelling the distribution of the vector mosquitoes Aedes aegypti and Culex pipiens in artificial containers. The selected model explained the occurrence of mosquitoes 59% better than chance as a function of the urbanisation × temperature categories and the natural lighting condition of the container. This novel zonation approach allows partitioning of environmental heterogeneity prior to the selection of study sites to avoid confounding gradients and provides multiple advantages, such as making comparisons across cities easier, extrapolating the results of site-scale experiments and identifying priority areas for control measures.

Author affiliation: Cardo, María Victoria. Universidad Nacional de San Martín. Instituto de Investigaciones e Ingeniería Ambiental. Laboratorio de Ecología de Enfermedades Transmitidas por Vectores; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Author affiliation: Vezzani, Dario. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución. Unidad de Ecología de Reservorios y Vectores de Parásitos; Argentina

Author affiliation: Rubio, Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de San Martín. Instituto de Investigaciones e Ingeniería Ambiental. Laboratorio de Ecología de Enfermedades Transmitidas por Vectores; Argentina

Author affiliation: Carbajo, Anibal Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de San Martín. Instituto de Investigaciones e Ingeniería Ambiental. Laboratorio de Ecología de Enfermedades Transmitidas por Vectores; Argentina

Abstract:

Background: Dengue cases have increased during the last decades, particularly in non-endemic areas, and Argentina was no exception in the southern transmission fringe. Although temperature rise has been blamed for this, human population growth, increased travel and inefficient vector control may also be implicated. The relative contribution of geographic, demographic and climatic of variables on the occurrence of dengue cases was evaluated.Methods: According to dengue history in the country, the study was divided in two decades, a first decade corresponding to the reemergence of the disease and the second including several epidemics. Annual dengue risk was modeled by a temperature-based mechanistic model as annual days of possible transmission. The spatial distribution of dengue occurrence was modeled as a function of the output of the mechanistic model, climatic, geographic and demographic variables for both decades.Results: According to the temperature-based model dengue risk increased between the two decades, and epidemics of the last decade coincided with high annual risk. Dengue spatial occurrence was best modeled by a combination of climatic, demographic and geographic variables and province as a grouping factor. It was positively associated with days of possible transmission, human population number, population fall and distance to water bodies. When considered separately, the classification performance of demographic variables was higher than that of climatic and geographic variables.Conclusions: Temperature, though useful to estimate annual transmission risk, does not fully describe the distribution of dengue occurrence at the country scale. Indeed, when taken separately, climatic variables performed worse than geographic or demographic variables. A combination of the three types was best for this task.

Author affiliation: Carbajo, Anibal Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina. Universidad Nacional de San Martín. Instituto de Investigaciones e Ingeniería Ambiental. Laboratorio de Ecología de Enfermedades Transmitidas por Vectores; Argentina

Author affiliation: Cardo, María Victoria. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina

Author affiliation: Vezzani, Dario. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina

Abstract:

Alien plants produce severe environmental and economic losses in the territories they invade. Modelling the spatial distribution of alien species as a function of the environment in the native range has therefore become an essential first step in the struggle against invasions. Phyla nodiflora var. minor is a fast-growing perennial herb native to South America that has spread through three continents, where it poses a major threat to biodiversity and significantly impacts on conservation and grazing systems, mainly in riparian areas. To assess the distribution of native Argentine populations of P. nodiflora as a function of the environment, we conducted long-term roadside surveys and associated the occurrence of the plant with climatic, geographical, demographical and vegetation cover variables in a generalised linear mixed model. The plant was recorded in 230 of 431 sites, mostly east of 66°W and north of 39°S. According to the best model, which predicted the data 58% better than random assignment, its occurrence was associated with temperature variables (mean annual values and daytime range) and relative humidity. Based on these associations, we generated a presence probability map for the occurrence of P. nodiflora in southern South America. Understanding the environmental determinants of the distribution of weeds in their native range provides valuable baseline data to further manage the spread of alien species.

Author affiliation: Sosa, Alejandro Joaquín. Fundación para el Estudio de Especies Invasivas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Author affiliation: Cardo, María Victoria. Universidad Nacional de San Martín. Instituto de Investigaciones e Ingeniería Ambiental. Laboratorio de Ecología de Enfermedades Transmitidas por Vectores; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Author affiliation: Julien, M.H.. Csiro Ecosystem Science and Biosecurity; Australia