Laboratory and Field Performances of WHO Approved Insecticides Used in Dengue Control Program

초록

Laboratory and field performances (WHO Prequalified Vector Control products) of temephos 1 G, temephos 50 EC as larvicide, Alphacypermethrin 10 SC and Lambdacyhalothrin 2.5% EC as adulticides were evaluated on different life stages of Aedes aegypti. Percent mortalities at different time intervals on recommended doses have revealed marked differences under laboratory and field conditions after the 5th day of application. In laboratory conditions maximum mortality percentage started from 98.29% after 48 hours of application, showed a dip on 4th and 8th day while for rest of the period till the 10th day fluctuated between 87.72 to 95%. The field mortality together with residual life was relatively lower as compared to laboratory test results. Under field conditions, maximum mortality started from 96.67% on day one and thereafter declined continuously to 38.33% in Lahore. A similar trend of decline was reported in Rawalpindi and Faisalabad i.e., 98.33 to 38.33% and 96.67 to 18.33% (P<0.001) respectively. Similarly, Temephos 50 EC gave field mortality between 100-83.33 till 5th day in three districts while in laboratory experiments it gave 100 to 98.33% mortality up to 10th day with few dips on 5th to 6th day of application. The field mortality rate declined rapidly from 10th day to 22nd days of application under field conditions. IRS with Alphacypermethrin 10 SC water based painted walls showed maximum mortality between 33.33-53.33% while on cemented walls the mortality remained very low i.e., 20-26.67% after 45 minutes of exposure. Lambdacyhalothrin 2.5% EC yielded maximum mortality of 90 % after 1hour of fogging in trials in places with high Aedes mosquito adults. We also checked the effect of distance of fogging on caged population and found that Aedes aegypti population fogged at 6 feet distance gave 88.75% mortality. We have concluded that according to WHO prescribed criteria on residual efficacy, insecticides, doses have different residual effect under laboratory and field conditions. The study therefore provides a strong basis for testing these chemicals against Aedes aegypti mosquitoes and redefining the application schedule for reducing the vector population.

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