A CSIRO-backed plan to release genetically modified mosquitoes in Queensland to combat dengue fever has sparked concern from scientists who suggest it could interfere with successful control programs and increase the risk of insecticide resistance.
Oxitec Australia, a collaboration between a British biotechnology firm and the CSIRO, has applied to sell a GM strain of Aedes aegypti mosquito, the main culprit for transmitting dengue and other viruses.
The strain, called OX5034 A. aegypti, prevents female mosquitoes from surviving into adulthood. Only female mosquitoes bite, spreading diseases to animals in the process.
Oxitec is proposing to sell the mosquitoes for Queensland residents to release. After release, they would breed with local A. aegypti mozzies, reducing populations.
An Oxitec Australia spokesperson said the sale of the strain would “be available to protect Australian communities” and released only after it passed “stringent government and regulatory approvals and undergoes extensive community engagement and consultation”.
But mosquito experts have criticised the proposal. “We should be very concerned about this release going ahead as planned,” said Dr Perran Ross, a scientist at the University of Melbourne who worked on mosquitoes for more than a decade.
“I’m not opposed to the [GM] technology in general but I am opposed to the approach they’re using, taking a foreign mosquito strain and then releasing that straight into the wild.”
The OX5034 strain is engineered from mosquitoes originating from Mexico. Though Oxitec has conducted field trials in the United States and Brazil, where the strain is commercially available, releases have not yet been tested in Australia.
Australian mosquitoes are uniquely susceptible to insecticides such as pyrethroids, Ross said. “There’s insecticide resistance almost everywhere else in the world. If you’re releasing a mosquito strain from a different country … there’s that risk that it might introduce genes that cause insecticide resistance.”
Climate adaptation was another concern, Ross said. “If you take mosquitoes from Mexico and bring them to Australia, you might get some genes that make them more tolerant to dry climates or other conditions. We don’t really know what the effect of that is going to be, but it is a potential risk.”
There are also concerns the Oxitec mosquitoes could interfere with success of Wolbachia programs, which have virtually eliminated dengue in far north Queensland.
Since 2011 mosquitoes infected with naturally occurring Wolbachia bacteria have been released in the state’s north as part of a World Mosquito Program initiative. The Wolbachia prevents the mosquitoes from transmitting viruses.
“Wolbachia has eliminated dengue as a public health problem over the last decade there,” said Prof Cameron Simmons, executive director of global delivery at the World Mosquito Program. “I can’t see anyone spending public funds, or even really private funds, to suppress A. aegypti mosquitoes with Oxitec GMO mosquitoes in far north Queensland.”
Ross said: “My major concern is the interference with the Wolbachia approach.
“They have very different objectives: the Wolbachia approach doesn’t aim to wipe out populations, it’s only replacing them with ones that don’t spread dengue as well.
“The GM mosquitoes are going to actually compete and wipe those ones out.”
A spokesperson for Oxitec Australia said: “There is no scientific evidence to suggest that there would be any negative interaction with mosquitoes that carry Wolbachia … We are committed to applying robust and transparent scientific processes to ensure that this technology is tested and is safe for deployment.”
Oxitec Australia has applied to the Office of the Gene Technology Regulator for a licence for commercial release. Public consultation on the proposal is expected to open in March; a public petition opposing the proposal was tabled in Queensland parliament last week.
Oxitec Australia says its mosquitoes could provide “an extra level of protection against dengue” in areas where Wolbachia has not been introduced – such as the Torres Strait, where there was an outbreak late last year – and “further reduc[e] the risk of dengue in areas where Wolbachia is present.”
Addressing insecticide concerns, Oxitec says its “Aedes aegypti mosquitoes have been proven to dilute resistance to insecticides among wild mosquito populations”.
“Oxitec’s technology is also sustainable, chemical-free, highly effective, and harmless to non-target species including mosquito predators,” a spokesperson said. “It will reduce dependence on pesticide-based controls, lowering environmental impacts and therefore help to protect native mosquitoes and other insect species like pollinators.”
