Targeted outdoor residual spraying, autodissemination devices and their combination againstAedesmosquitoes: field implementation in a Malaysian urban setting

Abstract

Currently, dengue control relies largely on reactive vector control programmes. Proactive vector-control using a rational, well-balanced integrated vector management approach may prove more successful for dengue control. As part of the development of a cluster randomized controlled epidemiological trial, a study was conducted in Johor Bahru, Malaysia. The study included one control site (three buildings) and three intervention sites which were treated as follows: targeted outdoor residual spraying only (TORS site, two buildings); deployment of autodissemination devices only (ADD site, four buildings); and the previous two treatments combined (TORS + ADD site, three buildings). The primary entomological measurement was per cent of positive ovitraps—ovitrap index (OI). The effect of each intervention on OI was analyzed by a modified ordinary least squares regression model. Relative to the control site, the TORS and ADD sites showed a reduction in the Aedes OI (−6.5%, P = 0.04 and −8.3%, P = 0.10, respectively). Analysis by species showed that, relative to control, the Ae. aegypti OI was lower in ADD (−8.9%, P = 0.03) and in TORS (−10.4%, P = 0.02). No such effect was evident in the TORS + ADD site. The present study provides insights into the methods to be used for the main trial. The combination of multiple insecticides with different modes of action in one package is innovative, although we could not demonstrate the additive effect of TORS + ADD. Further work is required to strengthen our understanding of how these interventions impact dengue vector populations and dengue transmission.

A Review: Autodissemination of Pyriproxyfen as Novel Strategy to Control Dengue Outbreaks

“…Another study was carried out to explore the additive impact of targeted outdoor residual spraying (TORS) and deployment of autodissemination devices (ADD) in Johor Bharu, Malaysia. Unfortunately, there was no significant effect on the mosquito populations following the combination of TROS and ADD (Hamid et al, 2020).…”

The iDEM trial (intervention for Dengue Epidemiology in Malaysia) to measure the effectiveness of integrated vector management with targeted outdoor residual spraying and autodissemination devices on the incidence of dengue in urban Malaysia: Study protocol for a cluster randomized controlled trial

“…Parts of corridors with such objects are not sprayed. Based on our ndings on the residual effects of K-Othrine® Polyzone [17,21], TORS is conducted every four months in all intervention areas.…”

“…The strategy for ADD deployment in these urban settings was adapted from In2Care standard recommendation (1 trap/400m 2 ), based on results from our pilot study in Johor Bahru, Malaysia [21] and another study evaluating the vertical infestation of Aedes in high-rise building [22]. Smart deployment of ADDs only on oors with higher expected mosquito density was found to be su cient to reduce the mosquito population in the whole building.…”

“…Plans to promote participant retention and complete follow-up Our previous study showed that regular contacts between the study population and the eld workers creates public trust [21]. To maintain adherence to the interventions, a liaison o cer assigned to each cluster contacts (via phone call or messaging) the building manager regularly to collect all complaints and feedback from the population.…”

“…The latter will be estimated over the baseline and intervention period in the 24 clusters selected for entomological monitoring. To quantify the effect of the interventions on the proportion of positive ovitraps, a modi ed ordinary least squares regression model using a robust standard error estimator will be implemented [21]. Using this model, the effect of the interventions will be quanti ed by the estimation of a difference of risk with its 95% con dence interval.…”