'Super' mosquitoes have now mutated to withstand insecticides, scientists say
One of the most vilified pest species on the planet continues to outsmart the ways in which humans attempt to get rid of them.
"Super" mosquitoes have evolved to withstand insecticides, according to new research -- and the most "sobering" finding is the high rate in which a species known for carrying disease has developed mutations.
Researchers at the National Institute of Infectious Diseases in Japan studied mosquitoes in dengue-endemic areas in Vietnam and Cambodia and found that they harbor mutations that endow them with strong resistance to common insecticides, according to a study published in Science Advances on Wednesday.
One of the most concerning mutations appeared in about 78% in collected specimens of 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.
Developing resistance pyrethroids often occurs when mutations appear in the Vgsc gene, which encodes the molecular target of pyrethroids, the paper states. The researchers discovered 10 new sub-strains of Ae. aegypti and noticed that one Vgsc mutation -- called L982W -- endowed mosquitoes with high resistance to the pyrethroid insecticide permethrin in the lab.
This mutation appeared with a frequency of more than 79% in mosquitoes collected from Vietnam, and mosquitoes in Cambodia harbored combinations of L982W and other Vgsc mutations that displayed “extreme” levels of pyrethroid resistance, the researchers said.
The L982W mutation has not been detected outside of Vietnam and Cambodia, but the researchers believe that it could be slowly spreading to other parts of the Asia.
The findings could pose a serious threat to infectious disease control and eradication programs, as the mutation is some of the highest insecticide resistance seen in a field population of mosquitoes, the researchers said.
Many health initiatives rely on pyrethroids and other insecticides to control mosquito-borne infections, especially for those that don’t have a vaccine, like dengue.
"It is important to be aware that the insecticides we normally use may not be effective against mosquitoes," Shinji Kasai, author of the study and senior research scientist of NIID's Department of Medical Entomology, told ABC News.
It will be necessary to continue to monitor these mutant alleles, especially in southeast Asia, to in order to take appropriate countermeasures before they spread globally, Kasai said. In addition, rotation of different insecticide group is sometimes effective, Kasai added.
"Governmental health officers should chose appropriate, more effective insecticide for controlling mosquitoes," he said.
Mosquitoes appear 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 the females learned to avoid pesticides after a single non-lethal exposure.
