Chinese scientists use intestinal bacteria to prevent mosquito-borne diseases

Chinese scientists use intestinal bacteria to prevent mosquito-borne diseases

Chinese scientists have developed a more natural strategy to prevent mosquito-borne diseases by changing the gut microbes of insects, which may be used as an alternative to controversial experiments that saw genetically modified mosquitoes released in Florida.

Mosquito-borne viruses, such as dengue and Zika, cause several fatal human viral infections. Dengue virus infects approximately 390 million annually worldwide.

Epidemic surveys over the past decade have documented frequent dengue outbreaks in Xishuangbanna and Lincang, both in Yunnan Province in southwestern China. But some have been reported in the neighboring cities of Wenshan and Pu’er.

The very different prevalence piqued the curiosity of researchers from Tsinghua University and the Yunnan Academy of Animal Science and Veterinary Science.

Gut microbes

The team’s field investigation of thousands of blood-sucking female mosquitoes revealed that mosquitoes from two different habitats carry different symbiotic bacteria in their guts, the first tissue organ that is usually infected with viruses.

Among the 55 strains isolated, a type of bacteria called Rosenbergiella_YN46 was abundant in the guts of mosquitoes in Wenshan and Pu’er, but not in Xishuangbanna and Lincang, according to a study published Friday in the journal Science.

Then, the researchers colonized the strain in the intestines of two mosquitoes that commonly carry the disease — Aedes albopictus and Aedes aegypti.

Those mosquitoes are less likely to contract dengue and Zika through blood bites, according to the study.

Further analysis suggested that an enzyme secreted by the bacteria could convert glucose into gluconic acid and rapidly acidify the intestines of blood-sucking mosquitoes. Mosquito-borne viruses will be neutralized in an acidic environment.

Intervention tactics

The team conducted experiments in the wild to breed “good mosquitoes” that did not transmit the virus. They added Rosenbergiella_YN46 bacteria to the water where mosquito eggs were laid and hatched.

Encouragingly, gut colonization proved successful at a site in Mengla District in Xishuangbanna and the colony continuously resided in the gut of Aedes mosquitoes.

The researchers also suggested another potential intervention strategy — the use of plants. Mosquito gut microbes in the wild either originate from microbes in the breeding waters, or in plant sap and nectar.

 

“We are currently collecting a large number of plant samples in Wenshan, where the bacteria were isolated, to look for plants enriched with these bacteria,” said Cheng Gong of Tsinghua, corresponding author of the paper. “Transplantation and cultivation of these plants into infected areas may interfere with the ability of mosquitoes to carry and transmit the virus.”

“If the plant is a shrub or herb, it can be planted in your yard or residential area,” Cheng added.

“Rosenbergiella_YN46 comes from the natural environment and the environmental risk potential is relatively low, and will not make mosquitoes resistant to drugs, and will not affect their survival in nature,” commented Xu Jianguo of the Chinese Center for Disease Control and Prevention, who did not take part of the study.

Meanwhile, the team is conducting research on the Leizhou Peninsula in southern China’s Guangdong Province, where the mosquito population is high but dengue is absent, to find more bacteria that can prevent the spread of the mosquito-borne virus.

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

This study has shown that the use of field mosquitoes colonized with bacteria may offer a viable biocontrol strategy to reduce virus transmission and prevalence in nature, the researchers said.