Can GMO insects be used to fight insects carrying dangerous pathogens that can harm and kill people?
Mosquitoes spread some of the most dangerous diseases on the planet that together kill hundreds of thousands of people every year. This includes malaria, dengue fever, West Nile virus, and yellow fever. According to WHO, there are 212 million cases of malaria and 429 000 of them die per year.
The traditional methods that are used to combat this includes harmful pesticides. However, these methods have limited effectiveness due to emergence and buildup of resistance. There are also concerns about the environment.
Thus, there is a need to develop other methods for vector control that does not rely on pesticides.
Before GMO insects, there was SIT
Another method that has been used is called Sterile Insect Technique (SIT). This involves the release of mosquitoes that have been sterilized with radiation into the wild. These will then mate with the wild type mosquitoes which reduce the reproduction of wild mosquitoes. This is because fewer proportion of matings will result in a viable offspring. In other words, mosquitoes will waste more time and energy on matings that do not produce new mosquitoes.
This method, however, is not without limitations. The major downside with radiation sterilization is that you have to do it continuously. Otherwise, population can recover after you stop. On the other hand, this can be seen as a benefit as the intervention is reversible.
There are ways to leverage genetic engineering methods to accomplish the same thing. This can be done in ways that is reversible (self-limiting), but also done in ways that is much more permanent (called self-sustaining).
But what about potential harms to the environment? Since each disease is only carried by a small number of insect species, they can be replaced or suppressed permanently without harm to the environment or the ecosystem. This is because many other species of mosquitoes or other insects can fill that ecological niche.
What about other downsides? The main limitations with this second approach is higher development costs and less post-release control. In contrast, sterile insect technique is relatively cheap and it is reversible by just stopping the release of those sterilized insects. The comparable benefit is that it can be done permanently.
Five Things to Know about Genetically Modified (GM) Insects for Vector Control is a paper written by Luke and Nina Alphey from the University of Oxford and published in PLoS Pathogens in 2014. It covers five basic questions when it comes to the prospect of GM insects: why researchers and public health experts would like to do it, how it is done using the tools of molecular biology, recent advances in cage and fields trials with GM mosquitoes, efficient methods for rearing high-quality mosquitoes and regulations, as well as how to find good target pests.
How are GMO insects made?
So how are GMO insects that can help fight disease vectors made? DNA is inserted into the genome of the insect with a transposon-based system. This means that the DNA is placed inside a transposon that is placed inside a plasmid. This is then injected into insect embryos with an enzyme called transposase. This helps the transposon move to the genome of the insect itself.
There are very many places in the genome that the transposon can be inserted, but it is more or less random. Because the transposon itself does not contain the gene for a transposase, the gene is stable inside the genome. This system typically also include a marker gene that can produce a protein that fluorescence under certain wavelengths of light so that the insects that have had a gene successfully integrated into the genome.
Currently, there are field trials with self-limiting genetic systems that have been shown to be successful. More invasive methods that would have more permanent effects are under development.
There are still many issues that remain. How can researches rear high-quality insects in sufficient numbers? How can quality in the field even be measured? Do we know enough about how the vector works and spread?
The researchers point out that this is not a magic bullet approach that will solve all problems, but a powerful technique with specific benefits and limitations that should be explored. In other words, multiple methods will need to be employed and that no single method should exclusively be relied on. This is needed to ensure that researchers deliver an approach that is safe for humans and the environment, that is highly effective against the vectors and is sustainable over time.
Will people accept GMO insects?
Can successful applications of GMO insects that target harmful vectors and reduce incidence of these terrible diseases overcome the resistance to biotechnology applications that involve genetic modification? Since there is so much fearmongering and nonsense being spread about GM crops (including many people wrongly insisting that they would never eat food with DNA in it), it is not a given that these GMO insects will be accepted, let alone embraced.
Perhaps the turn will happen when we see substantial drops in the incidence of these diseases. However, it is probably a good bet to predict that anti-GMO activists will oppose GMO insects, insist that they are harmful and attribute the disease incidence reduction on other factors. In a program that involves multiple methods, this may appear to be persuasive.