They find a high number of mosquitoes with a mutation that resists insecticides

Commentary

Insecticides that target disease-spreading mosquitoes run up against nature’s latest defense mechanism: evolution. Scientists reported Wednesday that mosquitoes in Cambodia and Vietnam are increasingly carrying a mutation that makes them resistant to a commonly used insecticide.

The reportin the journal Science Advances, tells the story of temples of the egyptians, vector of dengue, yellow fever, chikungunya, zika and other diseases. The researchers found that in Cambodia and Vietnam, 78 percent of the mosquitoes sampled had a mutation that, in laboratory studies, showed resistance to permethrin, which is part of a class of insecticides known as pyrethroids.

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That mutation has been seen before, but never with such a 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 that conferred resistance. One insecticide sprayed there killed only 10 percent of the mosquitoes, while the other killed none.

Insecticide resistance in mosquitoes is increasingly a public health problemparticularly as populations of temples of the egyptians and other species are growing and expanding their geographic range as a result of climate change, urbanization, and globalization.

The new study is a sobering reminder that efforts to combat mosquitoes will need to be as adaptable as the insects themselves.

The research also carries an echo of the pandemic and the evolution of SARS-CoV-2. The coronavirus it has repeatedly mutated in ways that improve its transmissibility and allow it to evade antibodies produced by vaccination or previous infection.

“I think our work will help us understand that evolution is a powerful force,” Shinji Kasai, lead author of the study and director of the department of medical entomology at the National Institute of Infectious Diseases of Japan, in an email.

Although this mutation in mosquitoes is still limited to Southeast Asia, temples of the egyptians he is a hardy traveler. It lays eggs that can survive for months in dry conditions and is potentially capable of spreading through global trade routes, Kasai said.

“Aedes mosquitoes can live anywhere. They like artificial water containers, including jars, used tires, plastic cups, basins, and pods,” he said. “I think it’s impossible to remove those water containers.”

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The report notes that although the mutation has not been detected anywhere in Southeast Asia except Vietnam and Cambodia, it may be spreading to other areas of Asia, where it could become an “unprecedented serious threat to human control.” of dengue fever” and others. mosquito-borne diseases.

Dengue infections have increased 30-fold in the past half century, with modelers estimating 390 million infections per year, according to the report by Kasai and 26 co-authors.

kasai noted that mosquitoes with this mutation are unlikely to thrive in areas that do not use pyrethroid insecticides. And he offered an overview of the long war between humans and mosquitoes, one that doesn’t assume that the insects will somehow be completely eradicated

“All organisms live as cogs on this planet and may be needed to sustain the planet,” he said in the email. “I think the most desirable world is one in which mosquitoes can be controlled to the extent that people do not have to feel the risk of contracting mosquito-borne diseases.”

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