Author(s)

Nurulhusna Ab Hamid^1*, Siti Nurfadhlina Mohd Noor¹, Mitra Saadatian-Elahi², Nur Rasyidah Isa¹, Rohaiyu Md Rodzay¹, Balqis Md Ruslan¹, Topek Omar³, Mohd Iqbal Mohd Norsham¹, Noor Hasmiza Amanzuri¹, Nurliyana Abd Khalil¹, Izzah Farhah Zambari¹, Muhammad Anwar Mohd Kassim¹, Muhammad Khairi Kamarul Zaman¹, Ainaa Mardia Bachtiar Effendi¹, Afiq Ahnaf Hafisool¹, Lee Teck Peng⁴, Brian Poong⁴, Mustafakamal Ibrahim⁵, Nurul Ashikin Roslan⁵, Lee Han Lim¹

¹Medical Entomology Unit, WHO Collaborating Centre for Vectors, Institute for Medical Research, Kuala Lumpur, Malaysia.
²Pôle Santé, Recherche, Risques et Vigilances Groupement Hospitalier Edouard Herriot Unité d’Hygiène, Epidémiologie et Prévention, Lyon, France.
³Vector Borne Disease Sector, Disease Control Division, Ministry of Health Malaysia, Putrajaya, Malaysia.
⁴Bayer Co. (Malaysia) Sdn. Bhd., Petaling Jaya, Malaysia.
⁵Hulu Langat District Health Office, Kajang, Malaysia.

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, while in the high-rise housing, there was also a significant decline in Ae. aegypti population in the semi-indoor environment. The evaluation of the residual bio-efficacy of deltamethrin SC-PE against laboratory-reared Aedes mosquitoes showed that the insecticide lasted longer in the high-rise housing compared to the low-rise housing with >80% mortality achieved continuously for 16 weeks. We provide initial evidence on residual efficacy of deltamethrin SC-PE in reducing Aedes population size in the low-rise and high-rise housing. Our results showed that ORS is a promising tool in the dengue vector control and like IRS in malaria control; it is a powerful and effective method if conducted correctly. However, large scale and well-designed studies with entomological and epidemiological endpoints are still warranted before its routine use in dengue control.

Indoor Residual Spraying, Outdoor Residual Spraying, Aedes, Deltamethrin SC-PE, Dengue, Vector Control, Ovitrap Index, Malaysia

Hamid, N. , Noor, S. , Saadatian-Elahi, M. , Isa, N. , Rodzay, R. , Ruslan, B. , Omar, T. , Norsham, M. , Amanzuri, N. , Khalil, N. , Zambari, I. , Kassim, M. , Zaman, M. , Effendi, A. , Hafisool, A. , Peng, L. , Poong, B. , Ibrahim, M. , Roslan, N. and Lim, L. (2019) Residual Spray for the Control of Aedes Vectors in Dengue Outbreak Residential Areas. Advances in Entomology, 7, 105-123. doi: 10.4236/ae.2019.74009.