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福建省福州市2020届高三上学期英语期末考试试卷
They still bite, but new research shows lab-grown mosquitoes are fighting dengue fever — a dangerous disease that they normally would spread. Dengue infections appear to be dropping fast in communities in Indonesia, Vietnam, Brazil and Australia that are filled with the specially grown mosquitoes.
Researchers first injected (注射)mosquito eggs with Wolbachia bacteria that's common in insects and harmless to people in a lab. Infected females then pass the bacteria on through their eggs. Releasing enough Wolbachia carriers, both the females that bite and the males that don't, allows mating(交配)to spread the bacteria through a local mosquito population.
Rather than using chemicals to wipe out pests, "this is really about transforming the mosquito," said Cameron Simmons of the nonprofit World Mosquito Program, which is conducting the research.
The first success came from Australia. Mosquitoes carrying Wolbachia were released in parts of North Queensland starting in 2011, and gradually spread through the local mosquito population. Dengue is spread when a mosquito bites someone who is infected, and then bites another person, but somehow Wolbachia blocks that — and local spread has nearly disappeared in those North Queensland Communities, Simmons said.
The studies are continuing in other countries. But the findings, presented at a meeting of the American Society for Tropical Medicine and Hygiene, suggest it's possible to turn at least some mosquitoes from a public health threat into annoying biters.
The work marks "exciting progress," said Michigan State University professor Zhiyong Xi, who wasn't involved with the project but has long studied how Wolbachia can turn mosquitoes against themselves.
More research is needed, specialists cautioned. "The results are pretty exciting — strong levels of reductions — but there clearly are going to be things to be learned from the areas where the reductions are not as great," said Penn State University professor Elizabeth McGraw.
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