One of the most reviled pest species on the planet continues to outwit the ways humans try to get rid of them.
“Super” mosquitoes have evolved to resist insecticides, according to new research, with the most “sobering” finding being the high rate at which a species known to transmit disease has developed mutations.
Researchers from Japan’s National Institute of Infectious Diseases studied mosquitoes in dengue-endemic areas in Vietnam and Cambodia and found that they harbor mutations that give them 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 the samples collected from Aedes aegypti, one of the most infamous mosquito species and a major vector of dengue, yellow fever and Zika virus, according to the study.
The development of resistant pyrethroids often occurs when mutations appear in the Vgsc gene, which encodes the molecular target of pyrethroids, the article states. The researchers discovered 10 new substrains of Ae. aegypti and noted 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 showed “extreme” levels of pyrethroid resistance, the researchers said.
The L982W mutation has not been detected outside of Vietnam and Cambodia, but the researchers believe it could 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.
Many health initiatives rely on pyrethroids and other insecticides to control mosquito-borne infections, especially for those without a vaccine, such as dengue.
“It’s important to note that the insecticides we normally use may not be effective against mosquitoes,” Shinji Kasai, study author and senior research scientist in NIID’s Department of Medical Entomology, told ABC News.
It will be necessary to continue monitoring these mutant alleles, especially in Southeast Asia, to take appropriate countermeasures before they spread globally, Kasai said. Also, rotating different groups of insecticides is sometimes effective, Kasai added.
“Government health officials should choose appropriate and more effective insecticides to control mosquitoes,” he said.
Mosquitoes seem to be evolving both physically and instinctively to avoid human attempts to eradicate their presence.
In February, scientists published research that mosquitoes are learning to avoid 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.