Insecticide resistance and, efficacy of space spraying and larviciding in the control of dengue vectors Aedes aegypti and Aedes albopictus in Sri Lanka S.H.P.P. Karunaratne a,⇑ , T.C. Weeraratne a , M.D.B. Perera b , S.N. Surendran c a Department of Zoology, Faculty of Science, University of Peradeniya, Peradeniya, Sri Lanka b Regional Office, Anti-Malaria Campaign, Kurunegala, Sri Lanka c Department of Zoology, Faculty of Science, University of Jaffna, Jaffna, Sri Lanka article info Article history: Received 27 September 2012 Accepted 14 May 2013 Available online 30 May 2013 Keywords: Dengue vectors Insecticide resistance Fogging Temephos abstract Unprecedented incidence of dengue has been recorded in Sri Lanka in recent times. Source reduction and use of insecticides in space spraying/fogging and larviciding, are the primary means of controlling the vector mosquitoes Aedes aegypti and Ae. albopictus in the island nation. A study was carried out to under- stand insecticide cross-resistance spectra and mechanisms of insecticide resistance of both these vectors from six administrative districts, i.e. Kandy, Kurunegala, Puttalam, Gampaha, Ratnapura and Jaffna, of Sri Lanka. Efficacy of the recommended dosages of frequently used insecticides in space spraying and larvi- ciding in dengue vector control programmes was also tested. Insecticide bioassay results revealed that, in general, both mosquito species were highly resistant to DDT but susceptible to propoxur and malathion except Jaffna Ae. aegypti population. Moderate resistance to malathion shown by Jaffna Ae. aegypti population correlated with esterase and malathion carboxylest- erase activities of the population. High levels of acetylcholinesterase (AChE) insensitivity in the absence of malathion and propoxur resistance may be due to non-synaptic forms of AChE proteins. Moderate pyrethroid resistance in the absence of high monooxygenase levels indicated the possible involvement of ‘kdr’ type resistance mechanism in Sri Lankan dengue vectors. Results of the space spraying experiments revealed that 100% mortality at a 10 m distance and >50% mortality at a 50 m distance can be achieved with malathion, pesguard and deltacide even in a ground with dense vegetation. Pesguard and deltacide spraying gave 100% mortality up to 50 m distance in open area and areas with little vegetation. Both species gave >50% mortalities for deltacide at a distance of 75 m in a dense vegetation area. Larval bioassays conducted in the laboratory showed that a 1 ppm teme- phos solution can maintain a larval mortality rate of 100% for ten months, and the mortality rate declined to 0% in the eleventh month. In the field, where 1 ppm concentration is gradually decreased with water usage, 100% mortality was observed only for the first four months, <50% mortality for the next two months, and 0% mortality was observed eight months after the application of temephos. Deltacide can be effectively used for space spraying programmes in Sri Lanka. Larval control can be successfully achieved through temephos with public participation. Ó 2013 Published by Elsevier Inc. 1. Introduction Aedes aegypti (Linnaeus) and Ae. albopictus Skuse are the major vectors of arboviral diseases such as dengue fever, yellow fever and chickungunya [1]. Dengue fever (DF) and dengue hemorrhagic fe- ver (DHF) are of major public health concern in Sri Lanka. During year 2009, over 32,000 cases and 315 deaths were reported across the country [2]. Sri Lanka also experienced an outbreak of chi- kungunya during 2006/2007 period [3]. In the absence of a licensed vaccine, the major focus in dengue disease control programmes of the island is vector control through elimination of breeding sites and application of insecticides. Spraying/fogging of insecticides has been widely used for several years in Sri Lanka to control den- gue vectors, especially during disease outbreaks. Four major groups of synthetic insecticides i.e. organochlorines, organophosphates, carbamates and pyrethroids, are commonly used in insect pest control programmes. Target site for organo- phosphates and carbamates is insect acetylcholinesterases. For pyrethroids and a group of organochlorines (DDT + its analogues) the target site is Na + channel regulatory proteins of the nerve membrane. For the rest of the organochlorines (cyclodienes), it is 0048-3575/$ - see front matter Ó 2013 Published by Elsevier Inc. http://dx.doi.org/10.1016/j.pestbp.2013.05.011 ⇑ Corresponding author. Fax: +94 81 2388018 E-mail address: shppk@pdn.ac.lk (S.H.P.P. Karunaratne). Pesticide Biochemistry and Physiology 107 (2013) 98–105 Contents lists available at SciVerse ScienceDirect Pesticide Biochemistry and Physiology journal homepage: www.elsevier.com/locate/pest