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A new crystal form of the insecticide is much more effective at fighting mosquitoes and malaria, researchers report.
Using a simple process of heating and cooling, the researchers developed a new crystal form of deltamethrin – a widely used insecticide used to fight malaria – that is up to twelve times more effective against mosquitoes than the existing form.
The findings in the Proceedings of the National Academy of Sciences could represent a much-needed and affordable insecticide alternative given the growing resistance of mosquitoes.
“Using more active crystal forms of insecticides is a simple and effective strategy to improve commercially available malaria control compounds to avoid the need for new product development in the ongoing battle against mosquito-borne diseases,” said Bart Kahr, professor of chemistry at New York University and a leading contributor to the study.
“Improvements in malaria control are still urgently needed during the global COVID-19 crisis,” says Kahr. “The number of deaths from malaria in Africa this year is expected to double due to supply chain disruptions related to coronavirus. We need public health action to curb both infectious diseases and, for malaria, that includes more effective insecticides. “
Malaria is a major public health challenge worldwide. More than 200 million cases and 400,000 deaths are reported each year. Insecticides like deltamethrin can prevent the spread of mosquito-borne diseases and are often sprayed indoors and on bed nets. However, mosquitoes are becoming increasingly resistant to insecticides, so researchers and public health officials are looking for alternatives with new mechanisms of action.
Many insecticides, including deltamethrin, exist in the form of crystals – the focus of research for Kahr and his chemical colleague Michael Ward. When mosquitoes step on insecticide crystals, the insecticide will be absorbed through their feet and, if effective, will kill them.
As part of their research on crystal formation and growth, Kahr and Ward study and manipulate insecticide crystals and explore their alternative forms.
For the new study, the researchers heated the commercially available form of deltamethrin to 110 ° C for a few minutes and allowed it to cool to room temperature. This resulted in a new crystallized form of deltamethrin made up of long, tiny fibers radiating from a single point.
In tests on Anopheles quadrimaculatus and Aedes aegypti mosquitoes – both transmit malaria – and fruit flies, the new crystal form of deltamethrin worked up to 12 times faster than the existing form. Fast-acting insecticides are important to quickly control mosquitoes before they multiply or spread further.
The new shape also remained stable for at least three months – and was able to kill mosquitoes quickly.
To simulate how the two forms of deltamethrin would work in curbing the spread of malaria, researchers turned to epidemiological models that suggest that using the new form in indoor spraying instead of the original form could cause malaria transmission itself in regions with a high percentage would significantly suppress the level of insecticide resistance.
In addition, less of the new form would be required to achieve the same effect, potentially reducing the cost of mosquito control programs and reducing environmental exposure to the insecticide.
“Deltamethrin has been a leading tool in the fight against malaria, but it faces an uncertain future threatened by the development of insecticide resistance,” said Ward.
“The ease with which this new crystal form of deltamethrin can be made, coupled with its stability and significantly higher potency, shows us that the new form can serve as a powerful and affordable tool for combating malaria and other mosquito-borne diseases.”
Additional co-authors are from the University of Puerto Rico and NYU. The National Science Foundation supported the work.