The Grapevine

Wolbachia Bacteria May Be Key To Preventing Mosquitoes From Transmitting Zika Virus

aedes aegypti
Aedes aegypti mosquitos that are infected with Wolbachia bacteria are released into the wild in order to combat the dengue virus. Gutemberg Brito IOC Fiocruz

A certain bacterium known as Wolbachia may be incredibly useful in building a new line of defense against the spread of Zika virus, according to a new study published in Cell Host & Microbe. Though Wolbachia has been studied in the past as an effective control agent for dengue virus and even malaria, this is the first time that scientists have found it might play a role in stopping Zika virus replication in Aedes aegypti mosquitoes.

In 2005, researchers first discovered that Wolbachia bacteria could fight mosquito-borne infections by significantly curbing the mosquitos’ transmission of viruses like dengue and chikungunya. Mosquitoes infected with the bacteria can’t replicate these viruses, and are thus unable to transmit it to other mosquitoes or humans. Historically, scientists have used this method as a way to prevent transmission of dengue virus, which lies in the same viral family as Zika.

The only issue, however, lies in the fact that Wolbachia don’t naturally infect A. aegypti mosquitoes. The trick has always been to inject A. aegypti mosquitoes with Wolbachia in the lab, then release them into the wild, hoping they’ll mate with others and spread this dengue “immunity.”

With the new study, the researchers argue that employing a similar method to A. aegypti mosquitoes may work as protection against Zika virus. “The idea has been to release Aedes mosquitoes with Wolbachia in the field over a period of a few months, so they mate with Aedes mosquitoes without Wolbachia living in the place and, over time, replace the mosquito population,” said Luciano Moreira of the Oswaldo Cruz Foundation, an author of the study, in a statement. “Zika and dengue belong in the same family of viruses, so with the outbreak in Brazil, the logical idea was to test the mosquitoes carrying Wolbachia by challenging them with Zika virus and see what would happen.”

The researchers examined non-infected Brazilian field mosquitoes as well as mosquitoes infected with Wolbachia as they were given Zika virus. Two weeks later, the infected mosquitoes had fewer viruses in their bodies and saliva compared to those that weren’t infected with Wolbachia. They were also deemed unable to transmit whatever viruses were left in their saliva, as the viruses were not active.

Earlier this year, the World Health Organization released a report encouraging scientists and health care workers to consider as many new ways of fighting the virus as possible. Attacking the outbreak at its source — the mosquitoes that carry it — is at the top of the agenda. Whether releasing mosquitoes back into the wild to carry Wolbachia through the generations will actually wipe out these viruses has yet to be seen.

Wolbachia showed to be as effective on Zika as the most important Dengue experiments we did,” Moreira said in the statement. “We know that there will not be only one solution for Zika — we have to do this alongside different approaches, like vaccines or insecticides, besides the public measures to control Aedes breeding sites.”

Source: Dutra H, Rocha M, Dias F, Mansur S, Caragata E, Moreira L. Wolbachia Blocks Currently Circulating Zika Virus Isolates in Brazilian Aedes aegypti Mosquitoes. Cell Host & Microbe. 2016.