The Skeeter Beater: A Hose Driven Insecticide Delivery Tool for the Control of Container-Breeding Mosquitoes (laboratory and preliminary field trials) Dr. Deon V. Canyon Dr. Jeffrey L. K. Hii School of Public Health and Tropical Medicine James Cook University, Townsville, Australia
Ae. aegypti Control Problems Well-watered, shaded and unkempt premises Breeding sites often difficult to treat Control operations not effective High cost to local authorities
Research aimed To develop a tool that Targets Ae. aegypti breeding sites Delivers an safe environmentally friendly insecticide with little wastage Targets unhatched eggs Economically distributes control costs throughout the affected population
Materials The Skeeter Beater Garden hose Trigger Device Container Water supply Dispersal control Mixes insecticide with water (reg. design Yates, Aust. designed to prevent backflow) Holds insecticide suspension Cost $30 The Mosquitoes and Eggs Ae. aegypti (COUNCIL strain) - Townsville
Materials The Insecticide - Bti (6AS VectoBac R ) Dose - 500 mg/l = 78 x LC 99 Townsville Ae. aegypti Overspray At 1.5 m from target = 81% of spray reaches target. Application time - 0.48 secs/target liter = 500 mg/l 1 sec. in 300mL pot base = 778 mg/l (122 x LC 99 ) 4 secs. in 5L bucket = 643 mg/l (101 x LC 99 ) Cost - Treat 120L water (Bti) = $2.40 (Abate) = $0.22
Methods and results Field dose confirmation Dilutions Scanner - 10 to 5000 mg/l - Pye spectrophotometer at 550-nm Calibration curve - slope: Y = 1.25E-04 X, r= 0.999 Bti concentration - highly correlated with % Absorbance Field Dose - 4 secs in a bucket with 5L of water Estimated = 643 mg/l Calculated = 966 + 32 mg/l
Methods and results Bti effect on egg hatching 6 intervention (Bti) and 6 control glass beakers - 300 ml Filter papers with 66 + 8 viable eggs (age 46-52 days) Hatch rates - Very high in treated beakers on 1st day Why? - Gjullin (1941) - Bacteria drops dissolved oxygen which stimulates egg hatching Use? - Mossie-Buster raises water levels 1.3 to 19% Exposed eggs hatch and larvae are killed
Methods and results Residual Effectiveness Egg and 1st instar bioassays (10 weeks) 4th instar bioassays (12 weeks) - WHO/VBC/81.807 1st instar - mortalities = 100% on week 10 4th instar - mortalities = 95% on week 10, 11, 12 Hatching - High in Bti beakers - week 1 & 2 - High again in week 9 in all beakers?? Dissolved oxygen Presumably lower in week 9 than in week 1 Another undetected stimulant to egg hatching?
Methods Preliminary Field Trials Site 1 Site 2 Site 3 - No rain, no sun, no organic matter - Rain, little sun, little organic matter - Rain, little sun, much organic matter Each site - buckets (5 treated + 1 control) Weekly Bioassays 1st instar (Site 1), 4th instar, egg hatch & water level Site 2 & 3 bioassays stopped at week 2 Effectiveness against wild recruitment 5 x 300 ml pot-bases & 5 x 800 ml plastic containers
Results Preliminary Field Trials Evaporation - 0.39 + 0.02 L/bucket/wk Hatch - No sig. dif. in Bti and Control hatch rates Site 1 1st instar mortality < 100% at week 8 4th instar mortality < 100% at week 5 1st instar mortality = 57% at week 10 4th instar mortality = 21% at week 12
Results Preliminary Field Trials On week 2 Site 2 - Rain diluted dose - 966 to 758 + 20 mg/l - Mortality = 95.1 + 0.88% Site 3 - Rain diluted dose - 996 to 683 + 11 mg/l - Mortality = 95.9 + 1.89%
Results Preliminary Field Trials Effectiveness against wild recruitment Plastic containers No recruitment Rain filled several times - dried out in 1 month Pot-bases Continuous Ae. aegypti recruitment Rain filled several times - dried out after 3-5 days Larvae never reached full development
Discussion Gardeners helped Can now use plant pot bases Must place pots away from sun & debris Problem Breeding Sites dealt with Skeeter Beater can easily treat: blocked gutters junk yards yards strewn with disposable containers difficult to reach areas
Discussion Problem Mosquito Harbourers dealt with They will pay control costs not City Councils They will be more liable = more responsible Councils will be able to apply more pressure Community-based action stimulated Commercial availability of a control tool will lead to greater community-based participation and action due to individual empowerment
Conclusion In 1992 Coluzzi said: Vector control has little or no place without new tools. A new control tool was developed which Effectively kills Ae. aegypti in areas with piped water Treats difficult to access urban breeding sites Deals with the problem of unhatched eggs Remedies ineffective control operations Spreads control costs over the effected population