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Spatial repellent evaluations in Thailand Brian P. Evans, Alongkot Ponlawat, Prasan Kankaew, and Jason H. Richardson Armed Forces Research Institute of Medical Sciences AFRIMS, 7 Jan 09 Outline • • • • • • • • Background Hypothesis Semi-field tunnel design Spatial repellency evaluation Challenges Advantages Future studies Questions Background • Disease reduction is dependent on minimizing humanvector contact. • Some approaches: – Skin repellents – ITNs/LLINs – Tarpaulins/tents – Clothing – Spatial repellents – Push-pull strategies Background • Most spatial repellents require a heat source to vaporize and release product. • Metofluthrin: – Vaporizes at ambient temperature – Vapor pressure 100-fold greater than permethrin – Led to development of metofluthrin-treated paper and metofluthrin-impregnated plastic strips. • Metofluthrin-impregnated plastic strips have not been evaluated against malaria vectors in Asia and against an Ae. aegypti colony from Thailand. Metofluthrin-impregnated Net (MIN) SumiOne® Net: - Kincho brand, Dainihon Jochugiku, Co., Ltd., Japan (Mushikonazu plate) - 60-d usage - 9 x 18 cm, 5.0 g - Metofluthrin content 5 % (w/w) + 95% ethylene-methyl methacrylate copolymer (w/w) AFRIMS, 7 Jan 09 Hypothesis • In a semi-field tunnel study, significantly fewer host-seeking An. dirus and Ae. aegypti are attracted to a human-baited tent with a MIN relative to a human-baited tent without a MIN over the long-term. Semi-field Tunnel Set-up Path Resident area Tent # 2, L Tent # 1, R Tree & grass area Tent # 4, L Tunnel # 2 ~ 300 m Tent # 3, R Tunnel # 1 AFRIMS, 7 Jan 09 Spatial Repellency Evaluation • MIN hung from inside of each treatment tent. • 150 host-seeking Ae. aegypti or An. dirus released at mid-point during specific time interval. • Interception traps emptied every hour by human volunteer acting as attractant. • Sentinel cups used to determine the effect of distance on efficacy of a MIN. • Mosquito net strips hung from tunnel to determine metofluthrin residual in non-treated fabric (WHO bioassay). Spatial Repellency Evaluation Control Sentinel Cup, 15 mos, 4 days old @ 10 m (4 cups) Tent # 2, L Treated Tent # 1, R ~ 1.9 m ~ 50 m ~ 2.4 m ~ 300 m Ribbons placed outside the tunnel for WHO cone assays and GCs Treated Tunnel # 2 Control Tent # 4, L Tent # 3, R ~ 1.9 m ~ 50 m Tunnel # 1 ~ 2.4 m AFRIMS, 7 Jan 09 Challenges • Other creatures entering tunnel • Calibration for An. dirus Advantages • Tropical climate year-round • Insectary: 4 Anopheles species, Ae. aegypti, Ae. albopictus • Expertise • Field sites Future activities • Evaluations of additional candidate spatial repellents • Semi-field large cage studies on “push”- “pull” technologies/approaches • Surveillance/control devices Acknowledgements • Mosquito Biology section, AFRIMS • MIDRP U