The effect of shade on the container index and pupal productivity of the mosquitoesAedes aegyptiandCulex pipiensbreeding in artificial containers

Abstract

The aim of this study was to assess whether certain attributes of larval breeding sites are correlated with pupal productivity (i.e. numbers of pupae collected per sampling period), so that these could be used as the focus for control measures to enhance control efficiency. Therefore, the objectives were to identify the months of highest pupal productivity of Aedes aegypti (L.) and Culex pipiens L. (Diptera: Culicidae) in an urban temperate cemetery in Argentina where artificial containers of < 6 L (flower vases) were the predominant breeding habitats, to compare various measures of the productivity of sunlit and shaded containers and to determine whether the composition of the containers affected pupal productivity. Over a period of 9 months, 200 randomly chosen water-filled containers (100 sunlit and 100 shaded), out of approximately 3738 containers present (approximately 54% in shade), were examined each month within a cemetery (5 ha) in Buenos Aires (October 2006 to June 2007). In total, 3440 immatures of Cx pipiens and 1974 of Ae. aegypti were collected. The larvae : pupae ratio was 10 times greater for the former, indicating that larval mortality was greater for Cx pipiens. Both mosquito species showed a higher container index (CI) in shaded than in sunlit containers (Ae. aegypti: 12.8% vs. 6.9% [chi(2) = 17.6, P < 0.001]; Cx pipiens: 6.3% vs. 1.8% [chi(2) = 24, P < 0.001]). However, the number and the density of immatures per infested container and the number of pupae per pupa-positive container did not differ significantly between sunlit and shaded containers for either species. Therefore, the overall relative productivity of pupae per ha of Ae. aegypti and Cx pipiens was 2.3 and 1.8 times greater, respectively, in shaded than in sunlit areas as a result of the greater CIs of containers in shaded areas. Neither the CI nor the number of immatures per infested container differed significantly among container types of different materials in either lighting condition. The maximum CI and total pupal counts occurred in March for Ae. aegypti and in January and February for Cx pipiens. The estimated peak abundance of pupae in the whole cemetery reached a total of approximately 4388 in the middle of March for Ae. aegypti and approximately 1059 in the middle of January for Cx pipiens. Spearman's correlations between monthly total productivity and monthly CI were significant at P < 0.001 for Ae. aegypti (r(s) = 0.975) and P < 0.01 for Cx pipiens (r(s) = 0.869). Our findings indicate that the efficacy of control campaigns against the two most important mosquito vectors in temperate Argentina could be improved by targeting containers in shaded areas, with maximum effort during species-specific times of year when pupal productivity is at its peak.

Tire-breeding mosquitoes of public health importance along an urbanisation gradient in Buenos Aires, Argentina

“…Observed seasonal patterns for both species through different urbanisation levels were similar to those previously reported in cemeteries of the Federal District (Vezzani et al 2004, Vezzani & Albicócco 2009, with the exception of Cx. pipiens in small towns, where an increasing trend persisted in autumn.…”

“…A similar trend was previously reported in flower vases within the study area (Vezzani & Albicócco 2009) and there is general consensus that there are higher frequencies of containers harbouring Ae. aegypti in shaded habitats (e.g., Focks et al 1981, Kittayapong & Strickman 1993, Vezzani et al 2005, Barrera et al 2006).…”

“…pipiens in urban temperate Argentina were published during the last decade. Both species are considered the most abundant species breeding in small artificial containers (García et al 2002, Vezzani & Albicócco 2009 and in adult collections on private premises . Within the Federal District, the spatial pattern of Ae.…”

Caracterización del consumo de larvas de culícidos (Diptera) en dos especies de peces indígenas de la zona central de Argentina

“…Estas especies son típicas de ambientes urbanos en varias partes del mundo, pudiendo criarse en recipientes artificiales de variados tamaños (Vezzani & albiCóCCo, 2009). Culex pipiens, además coloniza ambientes naturales lénticos de variados tipos y es la especie de culícido predominante en la zona central de Argentina, que es donde se realizó el estudio.…”

Mapping Entomological Dengue Risk Levels in Martinique Using High-Resolution Remote-Sensing Environmental Data

“…This variable was strongly inversely correlated with the NDVI, which evaluates the density of vegetation. Many studies have highlighted the association between shade potentially provided by vegetation and the presence of Aedes immature stages [30,39,40]. Shade may lower the very high water temperatures that have been specifically recognized as a negative factor for the presence of Aedes aegypti larvae [3].…”