Pyrethroid contact insecticides are mainstays of malaria control, but their efficacies are declining due to widespread insecticide resistance in Anopheles mosquito populations, a major public health challenge. Several strategies have been proposed to overcome this challenge, including insecticides with new modes of action. New insecticides, however, can be expensive to implement in low-income countries. Here, we report a simple and inexpensive method to improve the efficacy of deltamethrin, the most active and most commonly used pyrethroid, by more than 10 times against Anopheles mosquitoes. Upon heating for only a few minutes, the commercially available deltamethrin crystals, form I, melt and crystallize upon cooling into a polymorph, form II, which is much faster acting against fruit flies and mosquitoes. Epidemiological modeling suggests that the use of form II in indoor residual spraying in place of form I would significantly suppress malaria transmission, even in the presence of high levels of resistance. The simple preparation of form II, coupled with its kinetic stability and markedly higher efficacy, argues that form II can provide a powerful, timely, and affordable malaria control solution for low-income countries that are losing protection in the face of worldwide pyrethroid resistance.

拟除虫菊酯类接触杀虫剂是控制疟疾的主要手段，但由于蚊虫按蚊种群中普遍存在广泛的杀虫剂抗药性，因此其功效正在下降，这是主要的公共卫生挑战。已经提出了克服这一挑战的几种策略，包括具有新作用方式的杀虫剂。但是，在低收入国家实施新的杀虫剂可能很昂贵。在这里，我们报告了一种简单而廉价的方法，可以将溴氰菊酯（最活跃，最常用的拟除虫菊酯）的功效提高十倍以上，以对抗按蚊蚊子。加热仅几分钟后，I型市售溴氰菊酯晶体在冷却后熔化并结晶，形成II型多晶型物，它能更快地对抗果蝇和蚊子。流行病学模型表明，即使在存在高水平耐药性的情况下，在室内残留喷雾剂中代替II型剂型使用II型剂型也能显着抑制疟疾传播。形式II的简单制备及其动力学稳定性和显着更高的功效认为，形式II可为面对全球拟除虫菊酯抗药性而失去保护的低收入国家提供强有力，及时和可负担的疟疾控制解决方案。