Trials of Wolbachia-carrying mosquitoes scaled up in South America

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. 

A cross-section of an Anopheles mosquito that has been injected with Wolbachia.
A cross-section of Anopheles mosquito DNA that has been injected with Wolbachia (red). Researchers can now transfer the bacteria into Aedes mosquitoes, which reduces their capacity to transmit viruses to humans.
Credit: Penn State

Funding to the Eliminate Dengue Programme (EDP) from Wellcome, the Gates Foundation, USAID and the UK 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% 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 Wolbachia and 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 Wolbachia method in large urban areas, where these kinds of outbreaks can have such a devastating impact."

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