Researchers have completed a field trial demonstrating that the release of male Aedes aegypti mosquitoes, infected with the bacteria Wolbachia, can eradicate this important vector of dengue, Zika and chikungunya from central and southern Queensland towns.

Partly identified by their white lyre-shaped markings and their all-black proboscis, Aedes aegypti is responsible for transmitting 100s of millions of dengue cases annually across the tropical and sub-tropical world. The more severe form, dengue haemorrhagic fever leads to 25,000 deaths worldwide every year. As there are no vaccines for this virus, prevention relies almost exclusively on controlling the mosquito carriers.

An international collaboration between the University of Queensland, QIMR Berghofer, Michigan State University, James Cook University, CSIRO and Verily Life Sciences involved the release of millions of harmless male Aedes aegypti, infected with Wolbachia, across three trial sites in Northern Queensland. The trial demonstrated that the technique could dramatically suppress mosquito numbers and even eradicate this mosquito species from small Queensland towns.

The trial relied upon QIMR Berghofer’s capacity to cross Queensland mosquitoes with a Wolbachia-infected strain donated by Michigan State University. The head of QIMR Berghofer’s Mosquito Control Laboratory, Associate Professor Gregor Devine said: “We brought Wolbachia infected strain in from overseas, crossed it into our native Queensland Aedes aegypti and then demonstrated it was safe for release. Few labs have the capacity to do these types of experiments.”

Once approved for field-release the strain was shared with partners so they could implement the trial.

“When you release very large numbers of Wolbachia-infected males, almost all mating events result in no offspring. The wild population therefore crashes, sometimes to the point of local eradication,” Associate Professor Devine said.

Populations of this mosquito, uninfected with Wolbachia, occur in many small towns in central Queensland. Associate Professor Devine said, “These pose two major hazards: the possibility of local dengue outbreaks, and the transport and establishment of these mosquitoes to major urban centres like Brisbane.

The trial demonstrates that it’s a viable approach to dealing with these small, isolated populations,” he said.

“And we want to continue to share this strain,” said Associate Professor Devine, “…we have a number of low and middle income countries that we are currently working with so that they may also begin to think about implementing their own suppression or replacement strategies.”

Sources:
Queensland Health http://www.health.qld.gov.au/clinical-practice/guidelines-procedures/diseases-infection/diseases/mosquito-borne/dengue/virus-fever
World Mosquito program http://www.worldmosquitoprogram.org/en/learn/mosquito-borne-diseases/dengue
Rockhampton outbreak: https://doi.org/10.33321/cdi.2021.45.3
Trial paper: https://www.pnas.org/content/118/41/e2106828118