A deltamethrin crystal polymorph for more effective malaria control

Jingxiang Yang, Bryan Erriah, Chunhua T. Hu, Ethan Reiter, Xiaolong Zhu, Vilmalí López-Mejías, Isis Paola Carmona-Sepúlveda, Michael D. Ward, Bart Kahr

Research output: Contribution to journalArticlepeer-review


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.

Original languageEnglish (US)
Pages (from-to)26633-26638
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number43
StatePublished - Oct 27 2020


  • Deltamethrin
  • Epidemiological modeling
  • Malaria
  • Mosquito
  • Polymorphism

ASJC Scopus subject areas

  • General


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