Evaluation of a “fogging” canister for indoor elimination of adult Aedes aegypti.

Aedes aegypti is the primary vector for dengue transmission in Singapore. In response to dengue transmission, ultra-low volume (ULV) spraying of insecticides in apartments in transmission areas is used to supplement source-reduction effort. This study seeks to determine the efficacy of Mozzie Zap, a “fogger” in an aerosol canister, which contains 1.7% cypermethrin and 3.4% piperonyl butoxide (PBO, a pesticide synergist). The product, which has the unique continual release mechanism, was tested using two canisters in a two-bedroom apartment block. Caged female adult mosquitoes and magnesium oxide slides were positioned prior to the release of the chemicals. All bioassays and slides were exposed for 30 minutes before removal. Subsequent residual activity tests were carried out using WHO contact bioassay cones on horizontal (floor) and vertical (wall) surfaces. Mozzie Zap’s fog produced fog of effective droplet size (average VMD=24.32 μm), and achieved 100% mortality against Ae. aegypti. However, no residual activity on wall surfaces (3.1% on Day 2) was observed.

Evaluation of the grass infusion-baited autocidal ovitrap for the monitoring of Aedes adgypti (L).

Autocidal ovitraps used for the monitoring of Aedes (Stegomyia) aegypti (L.) (Diptera: Culicidae) in Singapore are routinely stocked with cow-grass (Axonopus commpressus) infusion. The optimum concentration of this infusion was determined to be a 1:4 dilution of a stock infusion prepared by fermenting dried cow-grass in tap water at a rate of 10g/l. Aedes aegypti females confined in an empty room and offered an ovitrap baited with cow-grass in competition with a range of common oviposition sites (plastic bottle, paper cup, plastic pail, flower pot plate, Coca-Cola can, and vase) laid significantly more eggs in the ovitrap than in the next most competitive container. The number of eggs laid in the ovitrap did not change with the competitiveness of the other sites offered, nor with the number of other sites, but it did change – albeit non-linearly – with the number of mosquitoes released. Implications for the interpretation of quantitative ovitrap data for the monitoring of mosquito populations are discussed.