Spatio-temporal analysis of the main dengue vector populations in Singapore

Abstract

Background Despite the licensure of the world’s first dengue vaccine and the current development of additional vaccine candidates, successful Aedes control remains critical to the reduction of dengue virus transmission. To date, there is still limited literature that attempts to explain the spatio-temporal population dynamics of Aedes mosquitoes within a single city, which hinders the development of more effective citywide vector control strategies. Narrowing this knowledge gap requires consistent and longitudinal measurement of Aedes abundance across the city as well as examination of relationships between variables on a much finer scale. Methods We utilized a high-resolution longitudinal dataset generated from Singapore’s islandwide Gravitrap surveillance system over a 2-year period and built a Bayesian hierarchical model to explain the spatio-temporal dynamics of Aedes aegypti and Aedes albopictus in relation to a wide range of environmental and anthropogenic variables. We also created a baseline during our model assessment to serve as a benchmark to be compared with the model’s out-of-sample prediction/forecast accuracy as measured by the mean absolute error. Results For both Aedes species, building age and nearby managed vegetation cover were found to have a significant positive association with the mean mosquito abundance, with the former being the strongest predictor. We also observed substantial evidence of a nonlinear effect of weekly maximum temperature on the Aedes abundance. Our models generally yielded modest but statistically significant reductions in the out-of-sample prediction/forecast error relative to the baseline. Conclusions Our findings suggest that public residential estates with older buildings and more nearby managed vegetation should be prioritized for vector control inspections and community advocacy to reduce the abundance of Aedes mosquitoes and the risk of dengue transmission.

Wolbachia-mediated sterility suppressesAedes aegyptipopulations in the urban tropics

“…As IIT programs scale up, the ability to maintain suppression over large areas with smaller release numbers is expected to reduce costs, improve sustainability, and minimize inconvenience to residents; avoiding excess release numbers should also reduce the likelihood of Wolbachia establishment due to the smaller number of females inadvertently released ( 33 ). With an effective monitoring system such as a network of traps ( 34, 37 ), programs could transition from regular releases to a risk-based approach, where releases are only performed when and where the vector population exceeds a certain threshold, or where releases are adapted to mosquito trap indices in an operationally manageable manner ( 33 ).…”

Fine-scale estimation of effective reproduction numbers for dengue surveillance

“…This is not surprising since impervious surfaces are a proxy indicator for urbanization, which provides favourable breeding habitats for Ae. aegypti mosquitoes that thrive in urban environments [46][47]. Next, the transmission intensity of dengue was positively associated with increased proportion of vegetation with structure dominated by human management (without tree canopy).…”

“…Next, the transmission intensity of dengue was positively associated with increased proportion of vegetation with structure dominated by human management (without tree canopy). This is likely due to the increased availability of water in leaf litter, soil surface, pots and in the discarded receptacles hidden in the foliage or shrub, which supports mosquito breeding [47][48]. In contrast, vegetation with structure dominated by human management (with tree canopy) was associated with lower dengue transmission intensity.…”

Climate variability and Aedes vector indices in the southern Philippines: An empirical analysis

“…Variation in the land use types and vegetation levels surrounding the residential areas surveyed is also likely to have influenced trends in indices between locations [ 34 ]. Previous studies have found that surrounding vegetation types and urbanisation levels to have substantial effects on adult Aedes species abundance, through providing a resting place and sugar source for adults, although the effect can be highly dependent on broader characteristics of the sampling location as well such as human socioeconomic and behavioural factors [ 43 , 44 ]. Each of these influences would be a useful variable to explore in future studies–particularly in the seven locations that consistently recorded above-threshold values in indices across multiple surveys.…”