J Med Entomol. 2014 Mar;51(2):387-91. doi: 10.1603/me13116.
In southern Punjab, Pakistan, Muzaffargarh District is known to have insecticide-resistant Anopheles and drug-resistant Plasmodium spp. In this part of the country, five anopheline mosquitoes, Anopheles stephensi Liston, Anopheles culicifacies Giles, Anopheles fluviatilis James, Anopheles superpictus Grassi, and Anopheles subpictus Grassi (Diptera: Culicidae) are known as malaria vectors. Among these, An. culicifacies is the primary and An. stephensi is the secondary malaria vector. Outbreaks of malaria usually occur after rainy episodes. We conducted field surveys to collect field strains of An. culicifacies and An. stephensi mosquitoes from different areas of Muzaffargarh District. We determined susceptibility and irritability levels of their adult stages to the discriminative dose of different insecticides. For this purpose, we used World Health Organization's established criteria for assessment. Mortality was calculated after 1 h exposure and for 24 h recovery period for various insecticides. An. stephensi was found to be significantly resistant to dichlorodiphenyltrichloroethane (DDT, an organochlorine), dieldrin (a chlorinated hydrocarbon), and malathion (organophosphorus), with lethal times (LT50) of 83.17, 52.48, and 37.53, respectively. However, the species was significantly sensitive to permethrin, deltamethrin (pyrethroids), and fenitrothion (organophosphate) with LT50 of 2.85, 2.34, and 13.18, respectively. Among these, permethrin showed more promising results against adult An. stephensi. When analyzed for irritancy, we found that among pyrethroids, permethrin was the most irritant insecticide for both An. stephensi and An. culicifacies. DDT and dieldrin showed least irritancy with 0.42 +/- 0.08 and 0.77 +/- 0.12 takeoffs per minute per adult, respectively, against An. stephensi. The mean number of takeoffs per minute per adult with permethrin showed significant irritancy for permethrin when compared with DDT. Based on this study, we conclude that the use of organochlorine (DDT) and chlorinated hydrocarbon (dieldrin) should not be reintroduced in Malaria Control Programme in Pakistan until there is enough evidence to do so at any stage in future, and the use of pyrethroids should continue, with preference to permethrin for better control of malariaby indoor residual spraying.
在巴基斯坦旁遮普省南部，木尔坦地区已知存在抗杀虫剂的疟蚊和抗药性疟原虫。在该国的这一地区，五种按蚊（疟蚊），即斯蒂芬斯氏疟蚊（Anopheles stephensi Liston）、致倦库蚊（Anopheles culicifacies Giles）、三带喙库蚊（Anopheles fluviatilis James）、史氏按蚊（Anopheles superpictus Grassi）和淡色库蚊（Anopheles subpictus Grassi）（双翅目：蚊科），被认为是疟疾的传播媒介。其中，致倦库蚊是主要媒介，斯蒂芬斯氏疟蚊是次要媒介。疟疾疫情通常在雨季过后爆发。我们在木尔坦地区的不同地区进行了实地调查，以收集致倦库蚊和斯蒂芬斯氏疟蚊的野外品系。我们确定了它们成虫对不同杀虫剂的鉴别剂量的敏感性和易激性水平。为此，我们使用了世界卫生组织制定的评估标准。在 1 小时暴露后和 24 小时恢复期内计算死亡率，以评估各种杀虫剂的效果。结果发现，斯蒂芬斯氏疟蚊对滴滴涕（一种有机氯杀虫剂）、狄氏剂（一种氯化烃）和马拉硫磷（一种有机磷杀虫剂）具有显著的抗药性，致死时间（LT50）分别为 83.17、52.48 和 37.53。然而，该物种对氯菊酯、溴氰菊酯（拟除虫菊酯类）和杀螟硫磷（有机磷类）非常敏感，LT50 分别为 2.85、2.34 和 13.18。其中，氯菊酯对成年斯蒂芬斯氏疟蚊表现出更有前途的效果。在分析易激性时，我们发现，在拟除虫菊酯类中，氯菊酯对斯蒂芬斯氏疟蚊和致倦库蚊都是最具刺激性的杀虫剂。滴滴涕和狄氏剂的易激性最低，每分钟每只成虫的起飞次数分别为 0.42±0.08 和 0.77±0.12。与滴滴涕相比，氯菊酯的平均每分钟每只成虫起飞次数表明其对氯菊酯具有显著的刺激性。根据这项研究，我们得出结论，在巴基斯坦的疟疾控制计划中，在任何阶段都没有足够的证据表明可以重新引入有机氯（滴滴涕）和氯化烃（狄氏剂），并且应该继续使用拟除虫菊酯，而氯菊酯则更优先用于更好地通过室内滞留喷洒来控制疟疾。
