September 20, 2019, by Brigitte Nerlich

The GM/gene drive communication confusion

The other day, I was at the airport waiting for a plane back to the UK, when I noticed on twitter that there was some kerfuffle going on about a field trial in Brazil intended to eliminate disease carrying mosquitoes, which had had, it seems, some unintended consequences (see study).

Here is a short summary: “A field experiment in Brazil that deployed genetically modified mosquitoes to control wild populations of the pest may be having unintended consequences. According to a genetic analysis of mosquitoes in the area, it appears the engineered stock has bred with wild mosquitoes and created viable, hybrid insects, scientists reported in Scientific Reports last week (September 10).”

Reading various tweets about the matter (especially this one), I immediately thought of ‘gene drive’ (a topic that I have covered before on this blog).

It turned out I was wrong, and if I had read the title of the study that people were tweeting about, I might have realised that, as it contains the word ‘transgenic’. Once back home and reading stuff properly, I started to think about why I got confused (jumped to conclusions) and why this might be important for science communication/gene drive communication. But first some background.

Diseases and mosquitoes

At the moment nearly 700 million people get a mosquito-borne illness each year resulting in over one million deaths. Mosquito-borne illnesses are diseases caused by bacteria, viruses or parasites transmitted by mosquitoes. Diseases transmitted by mosquitoes include malariadengueWest Nile viruschikungunyayellow fever, Zika and much more (Wikipedia). In the past, mosquitoes, and the diseases they spread, were confined to specific regions of our planet. However, international travel and global warming contribute to mosquitos, people and diseases globally.

Many efforts are being made to reduce the population of mosquitoes and to protect human populations from their bites.

Dealing with mosquitoes through genetic modification

Measures to deal with this health threat include sprays, nets but also genetically modifying mosquitoes. This can be done in two ways:

“The first is ‘population replacement’ in which a mosquito population biologically able to transmit pathogens is ‘replaced’ by one that is unable to transmit pathogens. This approach generally relies on a concept known as ‘gene drive’ to spread the anti-pathogen genes. In gene drive, a genetic trait – a gene or group of genes – relies on a quirk on inheritance to spread to more than half of a mosquito’s offspring, boosting the frequency of the trait in the population.

The second approach is called ‘population suppression’. This strategy reduces mosquito populations so that there are fewer mosquitoes to pass on the pathogen.”

(A good definition of gene drive can be found here Weiss, 2019; and more info here)

Unintended consequences

What about the genetic modification used in the case I read about at the airport? The insects created by the firm Oxitec and released in Jacobina, Brazil, are genetically modified to be sterile, but do not contain a gene-drive – so we are dealing, it seems, with population suppression. I had been wrong to jump to the gene drive conclusion (population replacement) when I first read about this case at the airport. As one article points out:

“Oxitec, a UK-based biotechnology company, has been testing whether genetically modified (GM) mosquitoes can suppress a population of non-modified mosquitoes since 2009. The strategy: deploy (non-biting) sterile male Aedes aegypti mosquitoes bearing a lethal gene that is passed onto the offspring and, as a result, will see the population plummet.”

The word ‘lethal’ is important here, and seems to be important to Oxitec, too. They used it prominently on a webpage in 2016 (now defunct) (see Nerlich and McLeod, 2016). On that webpage cells were metaphorically framed as machines. And…machines can be controlled! This means the ‘lethal’ (gene) can control the ‘deadly’ (diseases). In theory.

However, the study I read about seems to have shown that there were some problems (unintended consequences) with this ‘control’, namely that the transgenic or genetically modified mosquitoes transferred genes into the natural population – it seems. A widely reported article had the headline: “Failed GM mosquito control experiment may have strengthened wild bugs”.

This caused quite a lot of disquiet and started a conversation about risks relating to the release of GM mosquitoes, be they modified in conventional ways or through gene drive. As Kat Arney said in a twitter exchange about this experiment and gene drive: “yes, not a gene drive but a dominant lethal gene. interesting to ponder whether a gene drive would have behaved in the same way…”.

Lessons for science communication?

I won’t go into the disputes and discussions following the publication of the study, which are really interesting and deserve a separate and more thorough study. However, as somebody interested in how people communicate about gene drive, I think there are some lessons to be learned from this episode and some questions that need to be asked in terms of science communication.

Before I come to these lessons, let me just say that I don’t know whether the paper published in Nature Scientific Reports is overhyped or not. It may be. It has inevitably led to some overhyped headlines, talking for example about a mosquito apocalypse, about super-mosquitoes and mutants. That’s to be expected, however dangerous it may be.

When reading such reports, I came to realise how little I actually know about GM and gene drive mosquitoes. The question is: Would that matter if I was confronted with a choice of having mosquitoes in my locality managed using GM and/or gene drive methods?

And if I knew more, would I prefer one method over the other? The straight GM one, modifying genes and genomes, or the gene drive one, modifying ways of genetic inheritance (and one leading to suppression of insect populations and the other to replacement?). And what about the word ‘lethal’ used in communicating the first?

Beyond that, is it important to make clear that all gene drives are genetic engineering/modification but that not all genetic engineering/modification is gene drive? It is certainly important to point out that ‘gene drives’ are not the same as ‘genetically modified mosquitoes’, despite the fact that some genetically modified mosquitoes have been genetically modified using gene drive technology.

And finally, what would be the impact of such knowledge or lack of knowledge be on conversations about risk and about rejecting or accepting such technologies of insect and disease control in particular circumstances?

Added October, 2019 – some literature on the disputed study (this is just a list; it does not mean I endorse the opinions expressed in these articles)

Scare stories of mutant GM mosquitoes aren’t true, but have some truth

Dissent splits authors of provocative transgenic mosquito study

Study claimed a GMO trial went horrifically wrong. The study’s authors disagree 

Genetically modifying mosquitoes to control the spread of disease carries unknown risks

Oxitec’s GMO mosquitoes spread their genes in the wild? Separating science from hype after controversial new study

GM mosquitoes for insect population control: when speculative conclusions meet hyped journalism

(I would like to thank Aleksandra Stelmach for her helpful comments on this post)

Image: Mosquitoes, Pixabay


Posted in GMOsHypeinfectious diseasespublic engagement with sciencerisksynthetic biology