Heating deltamethrin may kill pesticide resistant mosquitoes

The insecticide is used to fight pests that spread deadly diseases such as malaria

A few minutes in the microwave produced a common insecticide found in lab experiments about ten times more deadly to mosquitoes.

Deltamethrin, a toxin, is used in home sprays and mosquito nets around the world to help prevent the spread of mosquito-borne diseases such as malaria. According to the World Health Organization, more than 400,000 people die each year. “Mosquitoes around the world are showing resistance to deltamethrin and [similar] compounds,” says Bart Kahr, a crystallographer at New York University who, by heating, helped develop a more potent form of deltamethrin.

This form of deltamethrin may have a better chance of killing insecticide-resistant pests, Kahr and colleagues reported online Oct. 12 in the National Academy of Science’s Proiding. Malaria is essentially eradicated in the United States, but more effective pesticides could be a blessing in areas like sub-Saharan Africa, where the disease is a major public health problem.

Kahr’s team increased the effectiveness of the commercial deltamethrin dust spray by simply melting a small bottle – either heating it to 150 degrees Celsius in an oil bath for five minutes or dipping it in a 700 watt microwave at the same time. While the microscopic deltamethrin crystals in the original spray have a random structure that resembles a mass of inconsistent flakes, the molten deltamethrin crystals solidify into a star shape when cooled to room temperature.
The chemical bonds between the deltamethrin molecules in the star shaped crystals are not as strong as in the original microcrystalline structure. “The molecules are really less fun or repaired,” Kahr said. When a mosquito lands on a star-shaped crystal dust, the deltamethrin molecule should be more easily absorbed into the insect’s body through its feet.

Researchers tested the most effective version of deltamethrin in laboratory-grown mosquitoes of two species: Anopheles quadrimaculatus, which can spread malaria, and Aedes aegypti, which can transmit other life-threatening diseases such as Zika and dengue fever. (SN: 1/8) / 19). Forty mosquitoes of each species were released in Petri dishes coated with the original deltamethrin dust spray and 40 more in a dish coated with a new form of insecticide.
This modified version of deltamethrin kills about half of mosquitoes exposed to A. quadrimaculatus in 24 minutes. In contrast, it took about five hours for the original spray to kill half of the exposed Anopheles – about twelve times as long. Also, it only took 21 minutes for the new spray to match the half of A. aegypti exposed, while the original spray lasted for over three hours.

Although A. quadrimaculatus can carry the parasite caused by malaria, this species of mosquito is native to North America, where the disease is not a major public health crisis. To make sure the new type of deltamethrin is effective in malaria hotspots around the world, “we need to conduct these experiments on species called Gambiae and Funestus, which are African Anopheles mosquitoes,” Kahr said. . and the six major malaria species Distribution of Anopheles species in South Asia.

Heat treating deltamethrin sprays “may increase their toxicity, but there are some obvious experiments we will have to do before we even consider adding it to the production system,” said Janet Hemingway of the Liverpool School of Tropical Medicine. in England. Who studies the resistance of insecticidal mosquitoes.

First, researchers need to test the new version of the insecticide against mosquito-resistant pesticides. Mosquito resistance to deltamethrin, along with other chemicals in the synthetic pesticide class known as pyrethroids, is a growing problem (SN: 6/29/12). “I guess … [the bugs] are extremely resistant to both forms,” ​​Hemingway said.
Specialists additionally need to ensure that the more harmful type of deltamethrin is alright for people, says Hemingway, who was not associated with the examination. “End – fascinating perception, however a long way from everything that could possibly be executed.”

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