The impact of body size on Aedes [Stegomyia] aegypti wingbeat frequency: implications for mosquito identification.

Billions of people are at risk due to mosquito-borne diseases. Ideally, the control of mosquito-borne diseases should integrate mosquito control and surveillance to maximize transmission prevention while minimizing environmental impacts. Mosquito surveillance is often limited in scope by logistical constraints, especially the labour and expertise in identifying captured mosquitoes. Mosquito sounds, primarily the wingbeat frequencies (WBF), have been extensively studied in the literature, often targeting a straightforward assessment of this technology with species identification in laboratory conditions. Optical sensors for measuring the WBF of free-flying mosquitoes are the most recent proposal to automate species identification. However, many of the factors that may influence WBF within and between species have not been fully examined, resulting in failures in the species identification. Here we show that body size and temperature modify the wingbeat frequency of female Aedes [Stegomyia] aegypti Linnaeus (Diptera:Culicidae) and such an optical sensor can capture these alterations. We demonstrate that this study's optical sensor can distinguish wingbeat frequency from large and small mosquitoes at different temperatures. The relationship between WBF and size should be taken into account to improve the accuracy of devices that automatically identify species using WBF.

Epidemiological and ecological characteristics of past dengue virus infection in Santa Clara, Peru.

To determine risk factors associated with dengue (DEN) virus infection among residents of Santa Clara, Peru, a rural Amazonian village near Iquitos, a cross-sectional serological, epidemiological and environmental survey was conducted. Demographic, social and behavioural information was obtained by standardized questionnaire from 1225 Santa Clara residents (61.3%) aged 5 years or older. Additional data were obtained on the environmental variables and immature mosquito species and abundance surrounding each household (n = 248). Sera that had been collected previously by the Peruvian Ministry of Health from residents were tested by an enzyme-linked immunosorbent assay (ELISA) for DEN virus IgG antibody. Antibody identity was verified as DEN by plaque reduction neutralization test. Data on individuals were analysed by univariate and multivariable methods, and independent sample t-tests. Spatial clustering was evaluated by comparing distances among DEN positive households. Overall, antibody prevalence was 29.4 % and more than doubled from the youngest to the oldest age groups, but did not differ by sex. Curiously, length of residence in Santa Clara was negatively associated with DEN virus antibodies. More frequent travel to Iquitos was positively associated with seroprevalence. Residents who obtained water from a river source rather than a local well also had significantly higher antibody prevalence. None of the environmental variables measured at each household corresponded to the patterns of antibody distribution. Of the larval mosquitoes found around residences, all were determined to be species other than Aedes. No evidence of spatial autocorrelation among antibody-positive households was detected. These results strongly suggested that recent DEN virus transmission did not occur in the village and that most infections of residents of this rural village were acquired while visiting the city of Iquitos.