EFFECT OF WASHING ON DELTAMETHRIN CONCENTRATION AND BIO-EFFICACY OF INSECTICIDE-TREATED MOSQUITO NETS

Abstract

The deltamethrin impregnated mosquito nets not only prevent but also control malaria, dengue fever and other vector-bone diseases. However, the deltamethrin concentration and bio-efficacy of mosquito nets can reduce due to washing. The purpose of this study is to investigate the effect of washing on deltamethrin concentration and bio-efficacy of military insecticide-treated mosquito nets. High Performance Liquid Chromatography method was used for the determination of deltamethrin in mosquito-nets. Then, the WHO recommended cone and excito-chamber methods were used to determine the bio-efficacy of mosquito nets. The deltamethrin concentrations in the mosquito-net were after no wash (4590±58.54 ppm), 1× wash (4020±47.39 ppm), 2× wash (3225±45.22 ppm), 3× wash (2771±107.5 ppm), 4× wash (2657±58.59 ppm), 5× wash (1835±47.55 ppm), 10× wash (957±34.85 ppm), 15× wash (197±22.54 ppm) and 20× wash (87±23.75 ppm). The mosquito knockdown effects were reduced by washing of net (no wash to 20× wash) after 60 minutes and 6 hours exposure range from 90-40% and 100-70%. The mosquito mortality rate was reduced by washing of net (no wash to 20× wash) after 24 hours exposure were reduced range from 100-80%. The mosquito repellent action was reduced by washing of net (no wash to 20× wash) after 10 minutes and 24 hours exposure, range from 90-30% and 100-60%. The effective bio-efficacy level was found in 5×wash (1835±47.55 ppm of deltamethrin).Therefore, mosquito net should be impregnated again after the 5× wash to obtain the best protection on the public from mosquito bite.