Gut bacteria in the fight against mosquito-borne diseases

Chinese scientists have developed a more natural strategy to prevent mosquito-borne diseases by altering the insects’ gut microbes, which could be used as an alternative to controversial experiments releasing genetically modified mosquitoes in Florida, Sihnua writes.

Mosquito-borne viruses such as dengue and Zika cause several potentially fatal viral infections in humans. Dengue viruses infect approximately 390 million people worldwide each year.

Epidemic research over the past decade has documented frequent dengue outbreaks in Xishuangbanna and Linkang, in southwestern China’s Yunnan Province. But there were few applicants in the neighboring towns of Wenshan and Puer.

The vastly different distribution piqued the curiosity of researchers from Tsinghua University and the Yunnan Academy of Animal and Veterinary Sciences.

The team’s field research on thousands of female blood-sucking mosquitoes found that mosquitoes from two different habitats carry different symbiotic bacteria in their guts, the first tissue organ commonly infected by viruses.

Among the 55 strains isolated, a type of bacteria called Rosenbergiella_IN46 was abundant in the guts of mosquitoes in Wenshan and Puer, but not in Xishuangbanna and Lincang, according to a study published April 19 in the journal Science.

The researchers then colonized the strain in the guts of two common disease-carrying mosquitoes – Aedes albopictus and Aedes aegypti.

According to the study, those mosquitoes were less likely to contract dengue or zika through the blood during the bite.

Further analysis showed that an enzyme secreted by the bacteria can convert glucose into gluconic acid and rapidly acidify the guts of blood-sucking mosquitoes. Viruses carried by mosquitoes will be neutralized in the acidic environment.

The team set up an experiment in the wild to breed “good mosquitoes” that don’t transmit viruses. They added the bacterium Rosenbergiella_IN46 to water in which mosquito eggs were laid and which hatched.

Encouragingly, gut colonization has been shown to be successful in Mengla County, Xishuangbanna, and the colony has persistently resided in the guts of Aedes mosquitoes.

The researchers also suggested another potential intervention strategy – the use of plants. The gut microbes of mosquitoes in the wild come either from microbes in the breeding waters, or from the sap and nectar of plants.

“We are collecting a large number of plant samples in Wenshan, where the bacterium was isolated, to find plants that are enriched with this bacterium,” said Cheng Gong of Tsinghua, co-author of the paper. “Transplanting and cultivating this plant in an infected area can affect the ability of mosquitoes to carry and transmit the virus,” he added.

“If those plants are shrubs or herbaceous plants, they can be grown in your yard or residential area,” Cheng added.

“Rosenbergiella_YN46 originates from the natural environment and its potential risk to the environment is relatively low and will not make mosquitoes resistant to the drug, nor will it affect their survival in the wild,” commented Su Jianguo of the Chinese Center for Disease Control and Prevention, who was not involved in the study.

Meanwhile, the team is conducting a study on the Leizhou Peninsula in southern China’s Guangdong province, where the mosquito population is high but dengue is free, to find more bacteria that could inhibit the spread of the mosquito-borne virus.

“The spread of Zika and epidemic encephalitis B could be contained if more bacteria are found,” Cheng said.

This study showed that the use of field mosquitoes colonized with the bacteria could offer a feasible biocontrol strategy to reduce virus transmission and prevalence in nature, the researchers said, Xinhua reported.