Residual Spray for the Control of <i>Aedes</i> Vectors in Dengue Outbreak Residential Areas

Abstract

The incidence of dengue in Malaysia has shown an increasing trend since the year 2000. Vector control is the primary approach for dengue control in Malaysia. There is an urgent need for new or modified approaches such as the residual spraying on the outer walls that can potentially last long enough to control the Aedes population, particularly in the outbreak-prone areas. In this field study, we conducted outdoor residual spraying (ORS) using a newly formulated polymer-enhanced suspension concentrate (SC-PE) of deltamethrin. The objectives of this study were to evaluate the efficacy of ORS using deltamethrin SC-PE and its effect on wild Aedes populations and to assess its residual bio-efficacy on painted cement walls against the pyrethroid-susceptible strains of laboratory-reared Aedes mosquitoes. Three rounds of spraying in a four-month cycle were conducted between 2014 and 2015 in four residential areas (low-rise and high-rise housing types) in Hulu Langat, Selangor. The bio-efficacy of the insecticide was evaluated by assessing its impact on vector population using ovitrap surveillance. Standard WHO wall deposit bioassay was adapted to determine bio-efficacy of deltamethrin, i.e. post 30 min knockdown and post 24 h mortality after exposure. During the treatment period, we observed significant reductions in the population of Ae. albopictus in the sprayed low-rise housing in both semi-indoor and outdoor environments,

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

“…outdoor vector control strategies could be used for Aedes control in densely populated urban districts. As reported in other investigations (Lee et al, 2015;Hamid et al, 2019) and in agreement with our results, TORS or ADDs effectively reduced the mosquito population. It can, therefore, be expected that co-application of these techniques together with public cooperation would further enhance the vector control efficacy.…”

“…K-Othrine Polyzone kills host-seeking and adult mosquitoes landing on the treated substrate, thereby lowering the number of adult mosquitoes in the area (Dunford et al ., 2018). Its use in TORS can potentially reduce the frequency of current insecticide applications for Aedes control due to its longer residual effect (Hamid et al ., 2019).…”

Semi-field evaluation of the bio-efficacy of two different deltamethrin formulations against Aedes species in an outdoor residual spraying study

“…Another study was later conducted using delta SC-PE 30 in the low-rise and high-rise residences. Bioassay results showed that the mortality percentage for Aedes was more than 80% for 16 weeks (Ab Hamid et al, 2019). Research in Tanzania using delta SC-PE showed to effectively cause 100% mortality in Blattella germanica for a period of 3 months even after exposure to sunlight, rainfall and daily temperature fluctuations (Kijlstra et al, 2014).…”

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.…”

“…Previous eld evaluation of TORS and ADDs showed effective reduction of the mosquito population [3,17]. In addition, the combination of insecticides with different modes of action in the same program is likely to limit insecticide resistance in the local Aedes vector population.…”