Researchers from Novel York University have developed a new crystal form of deltamethrin, a typical insecticide used to combat malaria, by a straightforward heating and cooling procedure. This insecticide is up to 12 times more potent against mosquitoes than the previous form.
In light of mosquitoes developing an increasing resistance to insecticides, the findings, which were published in the journal Proceedings of the National Academy of Sciences (PNAS), may offer a much-needed and reasonably priced alternative.
“The use of more active crystal forms of insecticides is a simple and powerful strategy for improving commercially available compounds for malaria control, circumventing the need for developing new products in the ongoing fight against mosquito-borne diseases,” said Bart Kahr, professor of chemistry at NYU and one of the study’s senior authors.
“Improvements in malaria control are needed as urgently as ever during the global COVID-19 crisis,” added Kahr. “The number of deaths from malaria in Africa this year is projected to double as a result of coronavirus-related disruptions to supply chains. We need public health measures to curtail both infectious diseases, and for malaria, this includes more effective insecticides.”
With more than 200 million infections and 400,000 reported fatalities each year, malaria is a significant public health issue around the world. Insecticides like deltamethrin, which are frequently applied inside and on bed nets, help stop the spread of diseases carried by mosquitoes.
Deltamethrin has been a leading tool in combating malaria, but it faces an uncertain future, threatened by developing insecticide resistance. The simple preparation of this new crystal form of deltamethrin, coupled with its stability and markedly greater efficacy, shows us that the new form can serve as a powerful and affordable tool for controlling malaria and other mosquito-borne diseases.
Professor Michael Ward
However, as mosquitoes are evolving a resistance to pesticides, scientists and public health professionals are looking for substitutes with fresh modes of action.
Kahr and fellow NYU chemistry professor Michael Ward’s study focuses on the crystal forms of many insecticides, such as deltamethrin. Pesticide is absorbed through mosquito feet when they step on insecticide crystals, and if it is successful, it kills the mosquitoes.
Kahr and Ward investigate the different forms of pesticide crystals as part of their investigation into crystal growth and formation.
In their PNAS paper, the scientists heated the readily available form of deltamethrin to 110°C/230°F for a short period of time and then allowed it to drop to room temperature. This produced a new crystalline form of deltamethrin, made up of long, microscopic threads radiating from a single point.
The novel deltamethrin crystal form outperformed the old form by up to 12 times when tested against the malaria- and fruit fly-transmitting mosquitoes Anopheles quadrimaculatus and Aedes aegypti.
Before they reproduce or continue spreading diseases, mosquitoes must be rapidly controlled with fast-acting pesticides. The new version was also stable and quickly effective for at least three months.
The researchers used epidemiological modeling to simulate how the two forms of deltamethrin would work to stop the spread of malaria. The results show that using the new form in indoor spraying instead of the original form would significantly reduce malaria transmission, even in areas with high levels of insecticide resistance.
Additionally, because the new form requires less of it to have the same impact, mosquito control operations may cost less and expose the environment to less insecticide.
“Deltamethrin has been a leading tool in combating malaria, but it faces an uncertain future, threatened by developing insecticide resistance. The simple preparation of this new crystal form of deltamethrin, coupled with its stability and markedly greater efficacy, shows us that the new form can serve as a powerful and affordable tool for controlling malaria and other mosquito-borne diseases,” said Ward.
