Approval given for experimental release of 750 million mosquitoes in the US
4 September 2020 / Oxitec is planning to release 750 million mosquitoes in Florida and Texas next year. According to the application, the plan is to only release genetically engineered male insects which will mate with wild female mosquitoes and produce offspring. Only the male offspring will be capable of surviving, whereas the inserted genetic construct is supposed to kill any female offspring. This effect is intended to carry on through following generations so that the mosquito population will be vastly reduced. The trials were approved by several US authorities at the end of August but still need approval of further local authorities. The start of the releases is planned for 2021.
If the trials are successful, billions of genetically engineered insects could be released in the next few years in an effort to extensively suppress or even eradicate yellow fever mosquitoes (Aedes aegyptii) in the region. The aim, amongst others, is to combat the spread of dengue fever. The mosquitoes carry the pathogenic virus as well as other viruses, e.g. the Zika and the yellow fever virus. Oxitec belongs to an investment company and is funded, amongst others, by the Bill & Melinda Gates Foundation.
There are, however, substantial risks associated with the release of the genetically engineered mosquitoes, in particular because they can reproduce and spread in the environment. It is known that the biological characteristics of the offspring of genetically engineered organisms can differ significantly to the ones originally intended. The reasons for this are genetic effects such as hybridisation with wild populations. Furthermore, mosquitoes and their larvae are exposed to a variety of environmental impacts during their life cycle.
These factors could possibly enable the survival of female insects. The dangers of being bitten by female genetically engineered mosquitoes were however not investigated because Oxitec declared that their technology would kill 100% of female offspring. Nevertheless, this assumption could turn out to be wrong: given the high number of released mosquitoes, it cannot be ruled out that due to unintended effects, the female insects develop resistance and therefore survive.
There are similar uncertainties inherent in the evaluation of other adverse risks for people and the environment. A lot of data that would be vital for reliable risk assessment are simply missing. Against this backdrop, Testbiotech urgently advises against the planned releases.
Even if the trials were to be successful, the benefits could possibly be either negligible or non-existent. There is another species of mosquito in Florida in competition with the yellow fever mosquito; this is the Asian tiger mosquito (Aedes albopictus), which is no less dangerous and can also transmit dengue fever. If the yellow fever mosquitoes were to disappear, this could promote the spread of the Asian tiger mosquitoes.
In the past, Oxitec trial releases of genetically engineered mosquitoes in Brazil have been the subject of contentious scientific debate. Even if the offspring of the mosquitoes did not survive in the trials and their genes were not supposed to be passed on, parts of the genome of the laboratory mosquitoes were nevertheless found in natural populations after the trials. The interpretation of these data is controversial, but the findings have not been disproved.
Oxitec’s plans are just some of a number of other projects aiming for large-scale genetic change in other wild species, e.g. insects, rodents, corals and trees. So-called gene drives are being developed to accelerate the spread of synthetic genes throughout natural populations. Many such projects have turned their attention to mosquitoes that could spread much more rapidly than the genetically engineered Oxitec mosquitoes. All these projects have one thing in common – a considerable increase in adverse risks for nature, people and the environment coupled with extensive uncontrollability. These problems are also a matter of discussions on international level such as the Convention on biological Diversity (CBD) and the EU.
Christoph Then, firstname.lastname@example.org, Tel.: +49 151 54638040