Objective:To examine the resurgence rate, house density index (HDI) and parous rate of the Aedes aegypti vector after space spraying carried out by the routine spraying team, and compare with the rates after standard indoor ultra low volume (SID-ULV) spraying carried out by the trained research spraying team.
Methods:Between March and September 2014, a cluster randomized controlled trial including 12 clusters (6 regular ULV, 6 SID-ULV) with totally 4 341 households was conducted, and around 20–31 houses in each cluster were selected for assessment. The parous rate and HDI of collected mosquitoes 2 days before and 1, 2 and 6 days after spraying were obtained and compared.
Results:The HDI dropped significantly from the baseline 1 and 2 days after spraying to a non-zero value in the SID-ULV treated locations but not in the regular ULV group locations. However, by 6 days after spraying, the HDI of both groups had returned to the base value measured 2 days before spraying. There were no statistically significant differences in the parous rate between groups.
Conclusions: SID-ULV is more effective in reducing Aedes aegypti populations. However, rapid resurgence of dengue vector after spraying in urban areas was observed in both groups.

Objective: To examine the resurgence rate, house density index (HDI) and parous rate of the Aedes aegypti vector after space spraying carried out by the routine spraying team, and compare with the rates after standard indoor ultra low volume (SID-ULV) spraying carried out by the trained research spraying team. Methods: Between March and September 2014, a cluster randomized controlled trial including 12 clusters (6 regular ULV, 6 SID-ULV) with totally 4. 341 households was conducted, and around 20-31 houses in each cluster were selected for assessment. The parous rate and HDI of collected mosquitoes 2 days before and 1, 2 and 6 days after spraying were obtained and compared. Results: The HDI dropped significantly from the baseline 1 and 2 days after spraying to a non-zero value in the SID-ULV treated locations but not in the regular ULV group locations. However, by 6 days after spraying, the HDI of both groups had returned to the base value measured 2 days before spraying. There were no statistically significant differences in the parous rate between groups. Conclusions: SID-ULV is more effective in reducing Aedes aegypti populations. However, rapid resurgence of dengue vector after spraying in urban areas was observed in both groups.

To demonstrate the effect of indoor spraying and window screens on Aedes aegypti mosquito density after space spraying. Methods: A total of 141 households (the study houses) in six communities of Songkhla City, located in Songkhla Province of southern Thailand, were randomly selected and the adult Ae. aegypti populations were assessed pre- and post-insecticide spraying from March to October, 2014. Houses close to (within a 20 m radius) the study houses were analyzed using spatial analysis tools. The Aedes aegypti density in the study houses and house density index were compared with the density in the neighbouring houses, based on three spraying conditions: (i) unsprayed (ii) only outdoor sprayed and (iii) indoor plus outdoor sprayed. Results: Only spraying houses indoors was the most effective (P<0.05). There was insufficient evidence that the source of the increase in the number of mosquitoes in unsprayed houses was due to their migration from neighbouring houses which had been sprayed. However, the study houses without screens on their windows were found to have a likely higher dengue vector population after spraying, but the difference was not significant. Conclusions: In dengue endemic areas, all houses should be fully screened and the number of houses ultra-low volume sprayed indoor plus outdoor should be increased with the cooperation of householders and communities during epidemics.