Estimating dengue vector abundance in the wet and dry season : implications for targeted vector control in urban and peri-urban Asia

Background: Research has shown that the classical Stegomyia indices (or ‘‘larval indices’’) of the dengue vector Aedes aegypti reflect the absence or presence of the vector but do not provide accurate measures of adult mosquito density. In contrast, pupal indices as collected in pupal productivity surveys are a much better proxy indicator for adult vector abundance. However, it is unknown when it is most optimal to conduct pupal productivity surveys, in the wet or in the dry season or in both, to inform control services about the most productive water container types and if this pattern varies among different ecological settings. Methods: A multi-country study in randomly selected twelve to twenty urban and peri-urban neighborhoods (‘‘clusters’’) of six Asian countries, in which all water holding containers were examined for larvae and pupae of Aedes aegypti during the dry season and the wet season and their productivity was characterized by water container types. In addition, meteorological data and information on reported dengue cases were collected. Findings: The study reconfirmed the association between rainfall and dengue cases (‘‘dengue season’’) and underlined the importance of determining through pupal productivity surveys the ‘‘most productive containers types’’, responsible for the majority (.70%) of adult dengue vectors. The variety of productive container types was greater during the wet than during the dry season, but included practically all container types productive in the dry season. Container types producing pupae were usually different from those infested by larvae indicating that containers with larval infestations do not necessarily foster pupal development and thus the production of adult Aedes mosquitoes. Conclusion: Pupal productivity surveys conducted during the wet season will identify almost all of the most productive container types for both the dry and wet seasons and will therefore facilitate cost-effective targeted interventions

Eco-bio-social determinants of dengue vector breeding : a multicountry study in urban and periurban Asia

Published in the Bulletin of the World Health Organization, no. 88, 2010Includes abstract in French, Spanish, and ArabicVector breeding and the production of adult Aedes aegypti are influenced by a complex interplay of factors. To achieve effective vector management of dengue, a public health response beyond routine larviciding or focal spraying is essential. Research findings showed that the most productive vector breeding sites were outdoor water containers, particularly if uncovered, beneath shrubbery, and unused for at least one week. Greater knowledge about dengue and its transmission was associated with lower mosquito breeding. This study focused on geographical areas, including private and commercial premises as well as public spaces and buildings, in six large and middle-sized Asian cities

Building and analyzing an innovative community-centered dengue-ecosystem management intervention in Yogyakarta, Indonesia

Background and Objectives: Dengue is an important public health problem in Yogyakarta city, Indonesia. The aim of this study was to build an innovative community-centered dengue-ecosystem management intervention in the city and to assess the process and results. Methods: For describing the baseline situation, entomological surveys and household surveys were carried out in six randomly selected neighborhoods in Yogyakarta city, documents were analyzed and different stakeholders involved in dengue control and environmental management were interviewed. Then a community-centered dengue-ecosystem management intervention was built up in two of the neighborhoods (Demangan and Giwangan) whereas two neighborhoods served as controls with no intervention (Tahunan and Bener). Six months after the intervention follow up surveys (household interviews and entomological) were conducted as well as focus group discussions and key informant interviews. FIindings: The intervention results included: better community knowledge, attitude and practices in dengue prevention; increased household and community participation; improved partnership including a variety of stakeholders with prospects for sustainability; vector control efforts refocused on environmental and health issues; increased community ownership of dengue vector management including broader community development activities such as solid waste management and recycling. Conclusion: The community-centred approach needs a lot of effort at the beginning but has better prospects for sustainability than the vertical “top-down” approach

Eco-bio-social determinants of dengue vector breeding: a multicountry study in urban and periurban Asia

Objective To study dengue vector breeding patterns under a variety of conditions in public and private spaces; to explore the ecological, biological and social (eco-bio-social) factors involved in vector breeding and viral transmission, and to define the main implications for vector control. Methods In each of six Asian cities or periurban areas, a team randomly selected urban clusters for conducting standardized household surveys, neighbourhood background surveys and entomological surveys. They collected information on vector breeding sites, people’s knowledge, attitudes and practices surrounding dengue, and the characteristics of the study areas. All premises were inspected; larval indices were used to quantify vector breeding sites, and pupal counts were used to identify productive water container types and as a proxy measure for adult vector abundance. Findings The most productive vector breeding sites were outdoor water containers, particularly if uncovered, beneath shrubbery and unused for at least one week. Peridomestic and intradomestic areas were much more important for pupal production than commercial and public spaces other than schools and religious facilities. A complex but non-significant association was found between water supply and pupal counts, and lack of waste disposal services was associated with higher vector abundance in only one site. Greater knowledge about dengue and its transmission was associated with lower mosquito breeding and production. Vector control measures (mainly larviciding in one site) substantially reduced larval and pupal counts and “pushed” mosquito breeding to alternative containers. Conclusion Vector breeding and the production of adult Aedes aegypti are influenced by a complex interplay of factors. Thus, to achieve effective vector management, a public health response beyond routine larviciding or focal spraying is essential