Zika virusBacteria-infected mosquitoes to combat Zika spread in South America

Published 27 October 2016

Mosquitoes infected with naturally occurring Wolbachia bacteria will be released in large urban areas in Colombia and Brazil. The new field trials will assess the effectiveness of the method for reducing new cases of Zika and other mosquito-borne diseases. Transferring the bacteria into Aedes mosquitoes reduces their capacity to transmit viruses to humans.

A cross-section of Anopheles mosquito DNA that has been injected with Wolbachia will be used in an effort to combat the spread of the Zika virus. Researchers can now transfer the bacteria into Aedes mosquitoes, which reduces their capacity to transmit viruses to humans.

The mosquitoes infected with naturally occurring Wolbachia bacteria will be released in large urban areas in Colombia and Brazil. The new field trials will assess the effectiveness of the method for reducing new cases of Zika and other mosquito-borne diseases.

The Wellcome Trust says that funding to the Eliminate Dengue Program (EDP) from Wellcome, the Gates Foundation, USAID, and the U.K. Department for International Development will be used to scale-up decades of research into this innovative infection control method.

Researchers from EDP have already conducted small-scale deployments of Wolbachia-carrying mosquitos in Australia, Vietnam, Indonesia, Colombia, and Brazil. The trials showed that where there are a lot of Wolbachia-carrying mosquitos in the area, there is no local transmission of the viruses. The new funding will allow large-scale trials to take place in sprawling urban areas, including Rio de Janeiro.

Wolbachia is a naturally occurring bacterium that is present in 60 percent of insect species worldwide. It significantly reduces the capacity of mosquitoes to transmit viruses to humans. Wolbachia is not, however, naturally present in Aedes aegypti mosquitoes, the primary vector for Zika, dengue, and chikungunya viruses. EDP researchers have pioneered a way to transfer the bacteria into Aedes mosquitoes.

When mosquitoes with Wolbachia are released into an area, they breed with local mosquitoes and pass the bacteria to their offspring. Within a few months, the majority of mosquitoes carry Wolbachiaand the effect is self-sustaining, without the need for further releases.

Dr. Mike Turner, Acting Director of Science and Head of Infection and Immunobiology at Wellcome, said: “This research is essential as it will help measure the health impact of the Wolbachiamethod in large urban areas, where these kinds of outbreaks can have such a devastating impact.”

“Wolbachia could be a revolutionary form of protection against mosquito-borne disease. It’s affordable, sustainable, and appears to provide protection against Zika, dengue, and a host of other viruses. We’re eager to study its impact and how it can help countries,” said Dr. Trevor Mundel, president of the global health division of the Bill and Melinda Gates Foundation.

“Zika and other diseases spread by [the Aedes aegypti mosquito] are really not controllable with current technologies,” said CDC director Dr. Thomas Frieden. “We will see this become endemic in the hemisphere.”

WHO data show that more than fifty countries have experienced an outbreak of Zika virus infections since 2015, and there have been nearly 2,200 cases of microcephaly – babies with brain damage – associated with Zika, twenty-eight of which have been reported in the United States. The vast majority of cases – 2,033 – were reported in Brazil.