Brian P. Evans, Alongkot Ponlawat, Prasan Kankaew, and Jason H. Richardson Armed Forces Research Institute of Medical Sciences Spatial repellent evaluations in Thailand 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 human- vector 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.

Resident area Path Tree & grass area ~ 300 m Tunnel # 2 Tunnel # 1 Tent # 1, RTent # 2, L Tent # 3, RTent # 4, L AFRIMS, 7 Jan 09 Semi-field Tunnel Set-up

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).

Ribbons placed outside the tunnel for WHO cone assays and GCs Sentinel Cup, 15 mos, 4 days 10 m (4 cups) Control Treated ~ 50 m~ 2.4 m ~ 1.9 m AFRIMS, 7 Jan 09 Spatial Repellency Evaluation Treated Control ~ 50 m~ 2.4 m ~ 1.9 m ~ 300 m Tunnel # 2 Tunnel # 1 Tent # 1, RTent # 2, L Tent # 3, RTent # 4, L

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