Could land cover influence Aedes aegypti mosquito populations?

Aedes aegypti is mainly found in urban environments, where human activity guarantees the permanent availability of potential larval habitats. The present study aimed to test for a possible association between Ae. aegypti infestation and land cover classes. From 23 February to 22 May 2015, immature mosquitoes (except eggs) were sampled in artificial containers identified in dwellings in Córdoba city, Argentina. The proportion of each land cover class was determined by SPOT-5 (Satellites Pour 1'Observation de la Terre or Earth-observing Satellites) image classification. Generalized linear models were developed to assess a suite of predetermined hypotheses and identified cover class variables associated with Ae. aegypti infestation. Arboreal vegetation was identified as the land cover with the greatest relative importance, negatively associated with Ae. aegypti mosquitoes. More infestation was find in areas with less arboreal vegetation, which corresponds to more urbanized areas.

Modelling the distribution of the vector Aedes aegypti in a central Argentine city.

Aedes aegypti (Diptera: Culicidae) is an urban mosquito involved in the transmission of numerous viruses, including dengue, chikungunya and Zika. In Argentina, Ae. aegypti is the main vector of dengue virus and has been involved in several outbreaks in regions ranging from northern to central Argentina since 2009. In order to evaluate areas of potential vector-borne disease transmission in the city of Córdoba, Argentina, the present study aimed to identify the environmental, socioeconomic and demographic factors driving the distribution of Ae. aegypti larvae through spatial analysis in the form of species distribution models (SDMs). These models elucidate relationships between known occurrences of a species and environmental data in order to identify areas with suitable habitats for that species and the consequent risk for disease transmission. The maximum entropy species distribution model was able to fit the training data well, with an average area under the receiver operating characteristic curve (AUC) of > 0.8, and produced models with fair extrapolation capacity (average test AUC: > 0.75). Human population density, distance to vegetation and water channels were the main variables predictive of the vector suitability of an area. The results of this work will be used to target surveillance and prevention measures, as well as in mosquito management.

Spatio-temporal dynamics of dengue 2009 outbreak in Córdoba City, Argentina.

During 2009 the biggest dengue epidemic to date occurred in Argentina, affecting almost half the country. We studied the spatio-temporal dynamics of the outbreak in the second most populated city of the country, Córdoba city. Confirmed cases and the results of an Aedes aegypti monitoring during the outbreak were geolocated. The imported cases began in January, and the autochthonous in March. Thirty-three percent of the 130 confirmed cases were imported, and occurred mainly at the center of the city. The autochthonous cases were more frequent in the outskirts, specially in the NE and SE. Aedes aegypti infestation showed no difference between neighborhoods with or without autochthonous cases, neither between neighborhoods with autochthonous vs. imported cases. The neighborhoods with imported cases presented higher population densities. The majority of autochthonous cases occurred at ages between 25 and 44 years old. Cases formed a spatio-temporal cluster of up to 20 days and 12km. According to a mathematical model that estimates the required number of days needed for transmission according to daily temperature, the number of cases begun to fall when more than 15.5 days were needed. This may be a coarse estimation of mean mosquito survival in the area, provided that the study area is close to the global distribution limit of the vector, and that cases prevalence was very low.