The development of predictive tools for pre‐emptive dengue vector control: a study of Aedes aegypti abundance and meteorological variables in North Queensland,Australia

Objectives To describe the meteorological influences on adult dengue vector abundance in Australia for the development of predictive models to trigger pre‐emptive control operation. Methods Multiple linear regression analyses were performed using meteorological data and female Aedes aegypti collection data from BG‐Sentinel Mosquito traps placed at 11 monitoring sites in Cairns, north Queensland. Results Considerable regression coefficients (R² = 0.64 and 0.61) for longer‐ and shorter‐term factor models respectively were derived. Longer‐term factors significantly associated with abundance of adult vectors were mean minimum temperature (lagged 6 month) and mean daily temperature (lagged 4 month), explaining the predictable increase in abundance during the wet season. Factors explaining fluctuation in abundance in the shorter term were mean relative humidity over the previous 2 week and current daily average temperature. Rainfall variables were not found to be strong predictors of A. aegypti abundance in either longer‐ or shorter‐term models. Conclusions The implications of these findings for the development of useful predictive models for vector abundance risks are discussed. Such models can be used to guide the application of pre‐emptive dengue vector control, and thereby enhance disease management.     

Residual insecticidal activity of long‐lasting deltamethrin‐treated curtains after 1 year of household use for dengue control

Objective To evaluate the residual insecticidal activity of the PermaNet^® curtains on Aedes aegypti after 1 year of use in Thai households and to assess the influence of sun and dust exposure, washing practices and detergent use. Methods We sampled UV‐protected PermaNet^® curtains made of a long‐lasting deltamethrin‐[55 mg/m²] treated polyester netting, before (10 curtains) and after 8 (10 curtains) and 12 months (66 curtains) of household use in a field site in Chon Buri, Thailand. We assessed the residual insecticidal activity of the curtains by standard WHO bioassay, using a deltamethrin‐susceptible insectarium Aedes aegypti strain. Results Mosquito mortality was 100% before distribution, 100% at 8 months and 98.2% (95% CI 97.9–98.5) at 12 months of use. Sunlight, hand‐washing and detergent use had no effect on the residual insecticidal activity after 12 months. However, the mosquito survival rate increased by a factor of 6.4 (95% CI 3.5–11.8) on machine‐washed curtains and by a factor of 2.0 (95% CI 1.4–2.9) on curtains not covered by dust. Conclusion The residual insecticidal activity of PermaNet® curtains remains high after 12 months use under field conditions.