The insecticides that target disease-spreading mosquitoes are running into nature’s ultimate defense mechanism: evolution. Scientists reported Wednesday that mosquitoes in Cambodia and Vietnam increasingly carry a mutation that makes them resistant to a commonly deployed insecticide.
The report, in the journal Science Advances, tells the story of Aedes aegypti, a vector for dengue, yellow fever, chikungunya, Zika and other diseases. The researchers found that in Cambodia and Vietnam, 78 percent of sampled mosquitoes had a mutation that, in laboratory studies, showed resistance to permethrin, which is part of a class of insecticides known as pyrethroids.
That mutation has been seen previously, but never at such high frequency in a mosquito population. The new study also found extreme resistance to two different insecticides sprayed in the Cambodian capital, Phnom Penh, where mosquitoes had more than one mutation conferring resistance. One insecticide sprayed there killed only 10 percent of mosquitoes, while the other didn’t kill any.