Pupal sampling for Aedes aegypti (L.) surveillance and potential stratification of dengue high-risk areas in Cambodia

OBJECTIVES To identify and describe the distribution of dengue vectors and factors affecting this distribution in Cambodia, with a view to practicing rational, evidence-based dengue outbreak prevention activities. METHODS Entomological survey with a questionnaire component in 100 randomly selected households in each of 13 clusters of high or low human population density of seven Cambodian provinces. Entomological and other indices were calculated, and statistical methods used to describe factors of potential outbreak risk. RESULTS Aedes aegypti was the principle dengue vector in all clusters, making up 95.5% (20555 of 21325) of the Aedes pupae population. The majority of pupae were recovered either from large concrete water storage jars (16230; 76.1%) or concrete water storage tanks (2819; 13.2%). There were small but significantly higher levels of dengue vector infestation in rural than urban areas. The mean pupae density over the survey was 16.4/house, which ranged between clusters from 5.2/house to 56.9/house. The 'pupae-per-person' index was 2.4 and 3.6 in urban and rural areas, respectively, and was independent of mean human population density or household water container distribution. CONCLUSIONS High populations of household-associated dengue vectors were present in all surveyed clusters. The highly skewed distribution of pupae in a limited number of key containers suggests adoption and further development of community-based control measures targeting these containers holds most potential chance of controlling dengue outbreaks in Cambodia.