Dengue protection by changing the mosquito’s microbiome?

Chinese scientists have developed a new strategy to prevent mosquito-borne diseases by changing insects’ gut microbes, as an alternative to experiments that see genetically-modified mosquitoes released in Florida.

Mosquito-borne viruses, such as dengue and Zika, cause several potentially fatal human viral infections. Dengue viruses infect approximately 390 million each year globally. In China, an epidemic survey over the past decade documented frequent dengue outbreaks in Xishuangbanna and Lincang, both in southwest China’s Yunnan Province. But few have been reported in neighboring cities of Wenshan and Pu’er.

The very different prevalence stimulated the curiosity of researchers from Tsinghua University and Yunnan Academy of Animal Science and Veterinary Sciences. Investigation on thousands of blood-sucking female mosquitoes revealed that mosquitoes from the two different habitats carry different symbiotic bacteria in their guts, the first tissue organ usually infected by viruses. Among the 55 strains isolated, a kind of bacterium called Rosenbergiella_YN46 was abundant in mosquito guts in Wenshan and Pu’er, but not in Xishuangbanna and Lincang.

Then, the researchers colonized the strain in the intestines of two common disease-transmitting mosquitoes — Aedes albopictus and Aedes aegypti. Those mosquitoes did become less likely to be infected with dengue and Zika via blood bites, according to the study. Further analysis suggested that glucose oxidase secreted by the bacteria can convert glucose into gluconic acid and rapidly acidifies the intestines of blood-sucking mosquitoes, rapidly neutralising the mosquito-borne viruses in acid environment.

As a consequence, the team tried to breed “good mosquitoes” that do not transmit viruses, by adding Rosenbergiella_YN46 bacteria to the water where mosquitoes eggs were laid and hatched. Encouragingly, the intestinal colonization proved a success at a site in Mengla County of Xishuangbanna and the colony persistently resided in the guts of Aedes mosquitoes.

The researchers also proposed another potential intervention strategy — the use of plants. Mosquito’s gut microbes in the wild are either derived from microbes in breeding waters, or in the sap and nectar of plants. They collected a large number of plant samples in Wenshan, where the bacterium was isolated, in order to find plants that are enriched with this bacterium. Transplanting and cultivating this plant to the infected area might intervene in the ability of mosquitoes to carry and transmit the virus. If those plants were shrub or herbaceous plants, they could even be grown in backyards or residential compounds.

This study has shown that the use of bacteria-colonized field mosquitoes could offer a feasible biocontrol strategy for reducing virus transmission and prevalence in nature.

Dengue protection by changing the mosquito’s microbiome?
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