Abstract
Dengue is transmitted mainly by the adult female Aedes aegypti mosquito. However, little is known about the impact of adult Aedes abundance on the risk of dengue transmission. Here we analysed nationally representative dengue case and vector surveillance data collected from Singapore, to determine the effect of adult Aedes abundance on the risk of dengue transmission. A case was an area with active dengue transmission as indicated by the presence of dengue cluster. A control was an area where no dengue cluster was reported. Using multivariate logistic regression, we analysed 88 cases and 602 controls and estimated the odds of dengue cluster formation at various adult Aedes abundance levels, estimated by the mean number of adult female Aedes per Gravitrap per week and categorised into Low, Moderate, High and Very High abundance level. We found that the risk of dengue cluster formation was positively associated with adult Ae. aegypti abundance. We observed a three to four-fold increase in the odds of dengue clusters forming in areas with High (AOR: 3.40, 95% CI: 2.09, 5.52) and Very High (AOR: 3.99, 95% CI: 2.46, 6.46) adult Aedes aegypti abundance level compared to those with low Ae. aegypti abundance level. Our study strengthens the evidence for the use of adult Aedes indices for dengue risk assessment and early warning for dengue outbreaks. Entomological indicators of adult Ae. aegypti could be used to anticipate and prioritize areas for dengue control.
Highlights
Dengue is currently regarded as one of the most important mosquito-borne viral diseases
Indices based on actual counts of adult Aedes are likely to be more useful in assessing transmission risk, but the adult Aedes population is rarely sampled as such sampling is perceived as time-consuming and difficult
In this study, which used national data from Singapore, we investigated the effect of adult Aedes abundance on the risk of dengue transmission
Summary
Dengue is currently regarded as one of the most important mosquito-borne viral diseases. Indices based on actual counts of adult Ae. aegypti are likely to be more useful in assessing transmission risk, but the adult Ae. aegypti population is rarely sampled as such sampling is perceived as time-consuming and difficult [6,11]. Another difficulty for adult sampling is the variability linked to the adult sampling tools since each sampling tool has its own attractiveness and can provide very different numbers when used in the same location [12].
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