Organism grown inside mosquitoes' bodies stops development of infectious parasite

Chinese scientists may have found a way to stop mosquitoes from spreading malaria, which kills one child every two minutes according to the World Health Organization.

Malaria affects between 200 and 300 million people worldwide every year according to the WHO. Infection is caused by Plasmodium, a parasite that is transmitted through mosquito bites.

A symbiotic bacterium that grows inside the bodies of mosquitoes was discovered by a team at the Institute of Plant Physiology and Ecology in Shanghai, and was genetically modified to carry anti-malaria genes that arrest the development of the parasites in the insects' intestinal tracts.

"The bacteria proliferate rapidly in the intestinal tracts of mosquitoes after they take in human blood and thus the ability to inhibit the development of the parasites will increase dramatically," said Wang Sibao, head of the research team at the institute, a branch of the Shanghai Institutes for Biological Sciences.

More important, the bacteria can be spread among mosquitoes quickly and widely during mating, and can be passed on to the next generation.

"When mosquitoes with such bacteria lay eggs in water, bacteria stuck to the surface of their eggs will propagate in the water and be ingested by the hatched larvae of the other mosquitoes, meaning that the capability of inhibiting the spread of the disease can be passed to other mosquitoes rapidly," Wang said.

A paper about the research team's findings was published on the website of Science, an international journal, on Friday.

The authors demonstrated that introducing 5 percent of male or female mosquitoes colonized with the symbiotic bacteria was sufficient for the bacteria to spread through the population and colonize 100 percent of mosquitoes for three subsequent generations, according to one peer review.

Another peer review said: "One of the bottlenecks of paratransgenesis has been the inability to maintain the bacteria in the insect for a prolonged period of time and, importantly, to spread the bacteria to the offspring. In this work, Wang showed that a specific bacterium found in mosquitoes can stay in the insect for a long period of time and be easily propagated to other mosquitoes."

Wang said laboratory tests have been completed, and the team will conduct field experiments in some African countries.

The research may bring new insight to approaches for inhibiting the spread of other infectious diseases, such as dengue fever, which is also spread by mosquitoes, according to the institute.

According to the National Health and Family Planning Commission, 3,189 Chinese citizens contracted malaria last year. It is increasingly difficult to prevent and fight the disease due to globalization. Only three of the cases last year were contracted locally.

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(China Daily 10/09/2017 page5)