BIOEFFICACY OF A LONG-LASTING INSECTICIDE IMPREGNATED NET AGAINST ANOPHELES MACULATUS THEOBALD AND CULEX QUINQUEFASCIATUS SAY.

This study was conducted to evaluate the bioefficacy and effects of unwashed and washed PermaNet® 2.0 nets treated with extrinsic heat during washing against mosquitoes under laboratory condition. The effectiveness of the washed nets was bioassayed soon after washing using the WHO cone test method. The results indicated that the treated nets exhibited high durability to washing (five washes) and persistent bioefficacy against An. maculatus on both unwashed and washed nets. The unwashed net exhibited mortality of 98.33 ± 2.06%, with KT50 and KT90 ranging from 17.57-to-66.38 minutes and 34.65-to-311.30 minutes, respectively (n = 9) for > 44 months. Nets washed at 30 °C for three successive washes exhibited mortality of 98.00 ± 2.65% (n = 3) for 7 months. Twenty-one months later, two washes at 80°C on the same nets caused a mortality of 87.50 ± 3.54% (n = 2). The overall cone mortality of five washes over a total wash period of 33 months was 94.75 ± 6.85% with KT50 and KT90 ranging from 23.98 to 58.25 minutes and 51.63 to 230.21 minutes, respectively (n = 5). However, the treated net exhibited lower bioefficacy against Culex quinquefasciatus on the unwashed nets with mortality of 9%. KT50 and KT90 ranged from 129.17 to 136.78 minutes and 315.35 to 716.05 minutes, respectively, over an unwashed period of 3 months (n = 1), and washed nets had a mortality of 30%; KT50 of 64.04 minutes and KT90 of 347.56 minutes for only one wash at 30°C (n = 1). Application of extrinsic heat treatment during washing at 30°C followed by increased heat at 80°C on the same net did not enhance any significant increase in mortality of An. maculatus and Culex quinquefasciatus (p > 0.05). There was a difference in the delayed knock down time soon after washing at 80°C. Based on these promising results, the PermaNet® 2.0 should be field-tested.