The benefits of releasing billions of genetically engineered mosquitoes into the environment has been exaggerated and the risks have been downplayed.
The results of its main experiments to date, conducted in Brazil, have not been published. Results from trials in the Cayman Islands show limited success. Computer modelling of the findings shows that 2.8 million genetically engineered adult male mosquitoes would need to be released per week to suppress a wild population of only 20,000 mosquitoes: impractical on any scale. There is no evidence of any reduction in the risk of dengue fever, which can continue even if the number of mosquitoes is reduced.
In Brazil, planned commercial releases are stalled whilst the health authority considers the limited evidence of efficacy and the broader risks. One concern is that releasing genetically engineered mosquitoes could even make the dengue situation worse, perhaps by reducing immunity to the more serious form of the disease.
Malaysia has abandoned mosquito trials and expects to roll out a new dengue vaccine later this year.
In Florida, dengue is not endemic and there have been no recent cases. To make a fully informed decision, local people need to be informed about the risks.
Panamanian researchers have warned that a competitor species, the Asian tiger mosquito, which also transmits dengue and chikungunya, could move in and be harder to eradicate. Disease transmission by this species might increase in the future.
Researchers in Germany have highlighted that some biting female genetically engineered mosquitoes will be released, and that Oxitec has not provided sufficient evidence that been bitten by, or swallowing, these mosquitoes will be safe.
Oxitec uses tetracycline as a chemical switch for the genetic killing mechanism in its genetically engineered mosquitoes. Survival rates of next-generation genetically engineered mosquitoes increase from 3 percent up to 18 percent when fed on industrially farmed meat, which is contaminated with the common antibiotic tetracycline. Tetracycline will be present in release areas in discarded takeaways, pet food and in some mosquito breeding sites such as septic tanks.
The use of tetracycline to feed genetically engineered mosquitoes in Oxitec’s mosquito factory risks spreading antibiotic resistant bacteria into the environment, posing a risk to human health. The non-veterinary use of tetracycline is being phased out in the United States and is already banned in many countries.
The regulatory process being followed by the Food and Drug Administration remains unclear. Company press releases should not replace the need for detailed evidence and public consultation on the risk assessment.