Use of transgenic Aedes aegypti in Brazil: risk perception and assessment.

Introduction In April 2014, Brazil's National Technical Commission on Biosafety--the agency officially responsible for the assessment of the risks posed by genetically modified organisms in Brazil--assessed the potential risks of the release in Brazil of the transgenic OX513A strain of Aedes aegypti and concluded that such a release would be safe. (1) At that point, Brazil became the first country to approve the unconstrained release of a genetically modified mosquito. Two years later, however, the Zika epidemic had added to the general public's concerns over the release of mosquitoes and we therefore decided to re-investigate the perceived risks and update the commission's risk assessment. Control of arbovirus vectors Several arboviruses--for example chikungunya virus, dengue viruses and, more recently, Zika virus--cause much human suffering in Brazil. (2,3) In 2015, for example, there were more than 1.5 million suspected cases of dengue fever in the country. (2) While attempts to create effective or cost-effective vaccines continue, control of the mosquito vectors remains of the utmost importance. (4) Brazil has had some success in controlling mosquitoes, even early in the 20th century when no effective insecticides were available. (5) Mosquito control, by residents, health workers and other municipal workers supported by a heterogeneous and broad set of collaborators, remains the focus of the National Dengue Control Programme. (6) However, the failure of this programme to reduce vector populations to levels that could interrupt dengue transmission (7) has spurred Brazilian interest in dengue vaccines (8) and novel approaches to vector control such as the sterile insect technique. (9-13) The International Atomic Energy Agency describes the sterile insect technique as "a type of birth control in which wild female insects of the pest population do not reproduce when they are inseminated by released, radiation-sterilized males". (14) Although sequential releases of large numbers of the sterilized males should lead to a reduction in the size of the pest population, the irradiation used can reduce the released insects' competitiveness--and this appears to be a particular problem when the insects involved are mosquitoes. (15) Over the last decade, as an alternative to the sterile male technique, the genetic modification of mosquitoes, with the production of large numbers of males and females that carry a self-limiting transgene, has been investigated. (16) Once released in the environment, the male insects carrying the transgene--which have to be produced in the presence of a selective agent that blocks the transgene's expression--should, potentially, compete on equal terms with the wild males. (17-20) The OX513 A strain of Ae. aegypti, which was developed by the British company Oxitec, expresses a self-limiting dominant transgene that is able to kill, at larval stage, the mosquitoes in which it is expressed (Fig, 1). (21) In the presence of tetracycline, the transgene is either not expressed or is only expressed at a very low and non-lethal level. Once released in the environment, most males carrying the transgene die after about two days. (21) [FIGURE 1 OMITTED] Risk perceptions and assessments In almost all countries, any living modified organism derived from modern biotechnology is very strictly regulated and subjected to a long and detailed risk assessment. (22) In Brazil, which is a Party to the Cartagena Protocol on Biosafety to the Convention on Biological Diversity, such risk assessment is the sole responsibility of National Technical Commission on Biosafety. (23) The commission consists of 27 members and an equal number of surrogates--chosen by various federal government agencies and civil organizations--including highly qualified scientists from across the country. As stipulated in the Cartagena Protocol, any risk assessment of a genetically modified product has to be supported with so-called hard data and preferably with hard data collected in the country that intends to use the product. …