One of the most maligned pest species on the planet continues to elude the ways in which humans try to get rid of them.
“Super” mosquitoes have evolved to resist insecticides, according to new research – and the most “sensible” finding is the high rate at which a species known to transmit disease has developed mutations.
Researchers at Japan’s National Institute of Infectious Diseases studied mosquitoes in dengue-endemic areas in Vietnam and Cambodia and found that they harbor mutations that confer strong resistance to common insecticides, according to a study published in Science Advances on Wednesday.
One of the most worrisome mutations appeared in about 78% of specimens collected from Aedes aegypti – one of the most infamous species of mosquito and a major vector of dengue, yellow fever and Zika virus, according to the study.
A municipal employee sprays mosquito repellent chemicals during a fumigation operation against Aedes Aegypti and Aedes Albopictus mosquitoes, responsible for transmitting Dengue, Zika and Chikungunya, on April 27, 2022 in San Salvador, El Salvador.
Afotografia/Getty Images, FILE
The development of pyrethroid resistance usually occurs when mutations appear in the Vgsc gene, which encodes the molecular target of pyrethroids, the article states. The researchers discovered 10 new sub-strains of Ae. aegypti and noticed that a Vgsc mutation – called L982W – endowed mosquitoes with high resistance to the pyrethroid insecticide permethrin in the laboratory.
This mutation appeared with a frequency of more than 79% in mosquitoes collected in Vietnam, and mosquitoes in Cambodia harbored combinations of L982W and other Vgsc mutations that exhibited “extreme” levels of pyrethroid resistance, the researchers said.
The L982W mutation has not been detected outside of Vietnam and Cambodia, but researchers believe it may be slowly spreading to other parts of Asia.
The findings could pose a serious threat to infectious disease control and eradication programs, as the mutation is one of the highest insecticide resistances seen in a field mosquito population, the researchers said.
Male Culicidae, carrier of tropical diseases, mosquito commonly called “dengue mosquito” in Brazil, is vector of chikungunya, yellow fever and dengue.
João Paulo Burini/Getty Images, FILE
Many health initiatives rely on pyrethroids and other insecticides to control mosquito-borne infections, especially for those that have no vaccine, such as dengue fever.
“It’s important to be aware that the insecticides we normally use may not be effective against mosquitoes,” Shinji Kasai, study author and senior investigator in the NIID’s Department of Medical Entomology, told ABC News.
It will be necessary to continue monitoring these mutated alleles, especially in Southeast Asia, to take appropriate measures before they spread globally, Kasai said. Also, rotating different groups of insecticides is sometimes effective, Kasai added.
“Government health officials should choose appropriate and most effective insecticides to control mosquitoes,” he said.
Mosquitoes seem to be evolving physically and instinctively to avoid human attempts to eradicate their presence.
In February, scientists published research that mosquitoes are learning to avoid the pesticides used to kill them.
Scientists who studied two species of mosquitoes – Aedes aegypti and Culex quinquefasciatus – found that females learned to avoid pesticides after a single non-lethal exposure.