Hyperresistant mosquitoes in Asia pose growing threat: study

Mosquitoes that carry dengue and other viruses are evolving to become more resistant to pesticides in parts of Asia, and new ways to control them are desperately needed, new study warns are doing.

Health officials typically blanket mosquito-infested areas with pesticide clouds, and resistance has long been a concern, but the scale of the problem was poorly understood.

Japanese scientist Shinji Kasai and his team examined mosquitoes not only in Ghana but also in several Asian countries, and found that a series of mutations made them resistant to common pyrethroid-based chemicals like permethrin. We discovered that it is virtually impermeable.

“In Cambodia, more than 90% of Aedes aegypti mosquito It has a combination of mutations that confer very high levels of resistance,” Kasai told AFP.

He found that some mosquito strains were 1,000 times more resistant, compared to the 100 times previously seen.

This means that an insecticide level that normally kills nearly 100% of the mosquitoes in the sample only killed about 7% of the insects.

Even a dose ten times stronger killed only 30% of the hyperresistant mosquitoes.

“The mosquito resistance levels found in Cambodia and Vietnam are completely different,” said Kasai, head of the entomology department at Japan’s National Institute of Infectious Diseases.

dengue fever can cause hemorrhagic fever According to the World Health Organization, more than 80% of infections are mild or asymptomatic, but an estimated 100-400 million people are infected annually.

Several dengue vaccines have been developed, and researchers are also using mosquito-killing bacteria to combat the virus.

However, neither option is close to eradicating dengue, and Aedes aegypti carries other diseases such as Zika and Zika. yellow fever.

need new formula

Resistance was also detected in another mosquito species, Aedes aegypti, but at lower levels. This is probably because they tend to forage outdoors, often eating animals, and may be less exposed to pesticides than the human-loving Aedes aegypti.

The study found that several genetic alterations are associated with resistance, two occurring near parts of the mosquito targeted by pyrethroids and several other insecticides.

Resistance levels vary, with some mosquitoes in Ghana, Indonesia and Taiwan being relatively sensitive to existing chemicals, especially high dose.

However, the study shows that “commonly employed strategies may no longer be effective.”

“There is growing evidence that the current location may not exist Insecticide It’s a formulation for controlling populations of major mosquito pests,” Webb told AFP.

He said new chemicals are needed, but officials and researchers should also consider other ways to protect communities, including vaccines.

“We have to think about pesticide rotation … different target sites,” Kasai added, whose study was published last month in the journal scientific progress.

“The problem is that there aren’t that many varieties available.”

Other options include more efforts to remove breeding grounds.

While it remains a mystery when and where the resistant strains emerged, Kasai is now expanding his research to other parts of Asia, looking at recent samples from Cambodia and Vietnam, and the 2016-2019 study. We are looking to see if anything has changed since then.

“I worry that mosquitoes with the mutations found in this study will spread worldwide in the near future,” he said.

“Before that, we have to come up with a solution.”

© 2023 AFP