London School of Hygiene & Tropical Medicine

The study, led by the Oswaldo Cruz Foundation, Brazil, is the first to show the effect of mosquito infection with Wolbachia bacteria on the transmission of Zika virus, a method that has previously been shown to reduce dengue virus transmission. The researchers investigated the effects of Wolbachia in Aedes aegypti mosquitoes, the main vector for dengue and the likely vector responsible for Zika outbreaks in the Americas.

Aedes aegypti mosquitoes infected with Wolbachia were significantly less able to transmit the Zika virus than those not containing the bacteria.  The Wolbachia-harboring mosquitoes were resistant to currently circulating strains of the virus, with greatly reduced levels in their abdomens. Importantly, their saliva did not contain infectious Zika virus, suggesting that this could help to control the disease in the human population.

Wolbachia is a naturally occurring bacterium that can infect arthropods, often existing in a mutual symbiosis inside insects such as mosquitoes. Researchers have previously infected Ae. aegypti mosquitoes, the main vector species for dengue and Zika viruses, with Wolbachia; this has been shown to successfully reduce the vectors' ability to transmit dengue. Since the bacteria are passed from the female mosquito to her offspring, it is thought to be a potential low-cost, self-sustaining control method.

Dr Thomas Walker, Lecturer at the London School of Hygiene & Tropical Medicine, previously created the line of Wolbachia-harboring Ae. aegypti mosquitoes used in this study. Commenting on the research, he said:

"This recent work in Brazil showing that the wMel strain of Wolbachia inhibits Zika virus in Aedes aegypti mosquitoes under laboratory conditions adds to growing evidence that these endosymbiotic bacteria can provide strong inhibitory effects on arboviruses of public health importance. 

"Releases of Wolbachia-infected Aedes aegypti mosquitoes are ongoing in several countries to determine if these naturally occurring bacteria can impact Dengue virus transmission.  Additional recent research in Colombia showing that the wMel strain of Wolbachia can also inhibit Chikungunya virus in Aedes aegypti suggest this novel biocontrol strategy could impact transmission of multiple arboviruses."

Publication:

• Heverton Leandro Carneiro Dutra, Marcele Neves Rocha, Fernando Braga Stehling Dias, Simone Brutman Mansur, Eric Pearce Caragata, Luciano Andrade Moreira. Wolbachia Blocks Currently Circulating Zika Virus Isolates in Brazilian Aedes aegypti Mosquitoes. Cell Host and Microbe. doi:10.1016/j.chom.2016.04.021