Aedes-borne virus disease control relies on insecticides to interrupt transmission. Temephos remains a key chemical for control of immature stage Aedes in Thailand and much of Southeast Asia. However, repeated use of insecticides may result in selection for resistance in vector populations, thus compromising operational intervention. Herein, the phenotypic response to temephos by Aedes aegypti (L.) and Aedes albopictus (Skuse) collected in Thailand and surrounding countries is presented. Data from 345 collection sites are included: 283 from literature review (244 sites with Ae. aegypti, 21 with Ae. albopictus, and 18 having both species sampled), plus 62 locations with Ae. aegypti in Thailand conducted between 2014 and 2018. Susceptibility assays followed WHO guidelines using the recommended discriminating dose of temephos (0.012 mg/liter) against late third to early fourth instar Ae. aegypti. Findings revealed 34 locations with susceptible Ae. aegypti, 13 with suspected resistance, and 15 indicating resistance. Published data between 1999 and 2019 in Thailand found Ae. aegypti resistant in 73 of 206 collection sites, whereas 3 locations from 11 sampled with low-level resistant in Ae. albopictus. From surrounding countries conducting temephos assays (Cambodia, Lao PDR, Myanmar, Malaysia, and Singapore), resistance is present in Ae. aegypti and Ae. albopictus from 27 of 56 and 19 of 28 locations, respectively. Routine insecticide susceptibility monitoring should be an operational requirement in vector control programs. Given the wide distribution and apparent increase in temephos-resistance, alternative larvicidal compounds must be considered if chemical control is to remain a viable vector control strategy.
The 2018 Asia Pacific Malaria Elimination Network's Vector Control Working Group (APMEN VCWG) annual meeting took place 3-5 September 2018 in Bangkok, Thailand. It was designed to be a forum for entomology and public health specialists from APMEN country programmes (over 90 participants from 30 countries) to discuss current progress and challenges related to planning, implementing, and sustaining effective vector control (VC) strategies for malaria elimination across the region, and to suggest practical and applicable solutions to these moving forward. The meeting was organised as a joint collaboration between the VCWG host institution-Faculty of Tropical Medicine, Mahidol University, Thailand-and leading partner institutions within the VCWG: Malaria Consortium and the Malaria Elimination Initiative at the University of California, San Francisco, Global Health Group (UCSF Global Health Group), under the leadership of the APMEN Director and VCWG Co-Chairs from ministries of health in Malaysia and India. This report provides an introduction to the role and nature of the VCWG, highlights key themes and topics presented and discussed at the meeting, and outlines the future objectives and focal areas for the VCWG and APMEN at large.