Succeeded in eradicating mosquitoes with the parasitic bacterium 'Volvakia'
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Mosquitoes not only cause unpleasant itching, but in recent years there has been a concern about the transmission of dengue fever by mosquitoes in Japan, and countermeasures against mosquitoes are urgently needed from the viewpoint of epidemic prevention. Under the circumstances, a paper that almost completely eradicated mosquitoes was published in the academic journal Nature due to the bacteria that control the breeding of mosquitoes.
Incompatible and sterile insect techniques combined combine mosquitoes | Nature
https://www.nature.com/articles/s41586-019-1407-9
World's most invasive mosquito nearby nearly two islands in China
https://www.nature.com/articles/d41586-019-02160-z
Parasite brings down mosquito numbers in parts of Guangzhou | New Scientist
https://www.newscientist.com/article/2210190-parasite-brings-down-mosquito-numbers-in-parts-of-guangzhou/
As a method of controlling mosquitoes, a method using a large amount of insecticide has been taken so far, and a method of releasing male mosquitoes sterilized by radiation has been studied. However, the use of insecticides has a large impact on the environment, and radiation causes sterilization of male mosquitoes to lose fertility, resulting in poor efficiency, and no remarkable effects were obtained.
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Under these circumstances, a research group of Professor Zhiyong Xi and others who are studying mosquito-borne infections at Michigan State University has succeeded in reducing mosquitoes by as much as 94% using certain bacteria widely distributed in nature. . The bacteria used in the experiment by the research group are the symbiotic bacteria named Bolbachia , which exist with high probability in arthropods including mosquitoes.
Professor Xi and others focused on this Bolbachia because it has the ability that 'Pervakia infected with males inhibits the reproduction of females not infected with the same strain as oneself'. It is speculated that Bolbachia, which transmits maternally like mitochondria, proliferates in an advantageous manner by preventing female pregnancy that is not infected with the same strain as the self.
In the figure below, the white gender mark means an individual who has not been infected with Wolbachia, and the red gender mark means an individual who is infected with Wolbachia. In the example at the top, it is natural for non-infected males and females to produce non-infectious offspring, but in the non-infected female and infected male cases there is no offspring. I understand.
by Stephen L. Dobson
Because the small island mosquitoes in Guangzhou, China, where the experiment was conducted, had already been infected with two types of Wolbachia, the research group infected male mosquitoes with the third Volbachia strain not present in the area. And released 160,000 animals per hectare. This means that we have succeeded in reducing Aedes albopictus in the area by 94%.
There is no new way to use Bolvakia, and in Brazil, in order to reduce the infection with dengue fever, in 2014, an attempt was made to release Aedes aegypti infected with Volvakia.
Succeeded in experiment to reduce population by more than 80% by depriving mosquitoes that transmit infectious diseases-GIGAZINE
However, this method has a problem that if the female that is infected with Wolbachia is mixed with the releasing mosquitoes, the infection of Wolbachia spreads, and the mechanism for preventing reproduction breaks down. It is said that 99% can be removed mechanically because female sanagi is larger than male sanagi, but the remaining 1% has to rely on human vision, which increases costs There was an issue called.
However, the research team succeeded in removing only female mosquitoes while maintaining almost the male reproductive ability by irradiating a low dose of radiation. 'This has made it possible to produce a large number of male mosquitoes infected with Wolbachia reliably and at low cost,' says Xi.
Stephen Dobson, a professor of entomology at the University of Kentucky and founder of MosquitoMate, a pest control company that has already adopted the control method by Wolbachia, said, “How to use pesticides and the water that mosquitoes laid eggs. It is no longer possible to get rid of mosquitoes by throwing it away. ' The reason is that mosquitoes are already resistant to common insecticides and can also reproduce in places where human eyes can not reach them.
“The method using Bolbachia is large-scale, as it is conditional on the fact that mosquitoes in a certain area are not infected with a specific strain of Volvakia,” said Gordona Rasic, a molecular ecologist at the Queensland Institute of Medical Sciences in Australia. 'This is not suitable for public health measures,' said the study as promising as a preventive measure to reduce the risk of mosquito-borne infections.
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