The techniques of genetic edition have drawn a new horizon of possibilities that are just beginning to discover, as we find potential applications for this technology.
Now, a group of scientists from the University of California at San Diego has decided to explore one of these new paths by applying this technology to epidemiology. More specifically, they have carried out an experiment, published in the specialized media Current Biology , in which the CRISPR-Cas9 technique is used to reduce the ability of certain types of mosquitoes to transmit infectious diseases.
Mosquitoes blind to humans
The Aedes aegypti mosquito , commonly known as the mummy mosquito, is an important vector of tropical fevers such as dengue, yellow fever, Zika or chikungunya; diseases that together affect millions of human beings around the world each year.
Therefore, for years strategies have been sought to control their populations (which, thanks to global warming, grow and appear in places where the insect was not previously endemic, such as Spain) and protect people from their bite.
Along these lines, the authors of this research set out to modify these mosquitoes with a gene that makes it difficult for them to detect human prey and that is heritable, so that the desired mutation is spread through a specific mosquito population. If this works, not only will the bites decrease and therefore the risk for people, but a certain population should be considerably reduced as the females (who are the ones that bite us) have a new difficulty in feeding.
When hunting, Aedes aegypti females (which are diurnal active) rely on various senses, although the main ones are CO2 detection (emitted by the respiration of land animals) and vision (mosquitoes are attracted to dark areas in their field of vision). When they approach a potential victim, they also detect it by the heat it emits and the smell it gives off.
For this reason, the researchers found out which are the visual pigments present in the eyes of the female mosquito (mainly two, Op1 and Op2) and used the CRISPR technique to eliminate each one of them separately and both in conjunction.
Graph showing the effect of Op1 and Op2 elimination in Aedes aegypti mosquitoes.Graph showing the effect of Op1 and Op2 elimination in Aedes aegypti mosquitoes.Craig Montell et al. / CURRENT BIOLOGY
What they found is that mosquitoes from which one of the pigments had been removed behaved the same as those who had both, but those from which both had been removed did not target dark objects , despite continue to react (albeit in a weaker way) to some visual stimuli.
That is, the mosquitoes, without being completely blind, had lost the detection mechanism for potential prey that led them to head towards dark objects . In a way, this genetic modification could be considered to make humans (and other animals) invisible to mosquitoes.
Towards future application
The results are promising, but the application of this type of technology is something very delicate . In fact, it is not the first time that the possibility of modifying mosquitoes with RISPR-Cas9 has been investigated, but so far none of the experiments that have been carried out have been able to be put into practice outside the laboratory.
In particular, there are certain fears that the decline in the mosquito population may have effects on the ecological balance that are often very difficult to predict. For example, the males of several species of mosquitoes play an important role as pollinators, so their disappearance could have serious consequences for the plants that depend on them.
Another fear that has been formulated is the possibility that the disappearance or reduction of mosquitoes leaves an ecological niche that is filled by other species of mosquitoes, some of which could also transmit serious diseases to people.
This does not mean that there is no future for this class of technologies, but rather that it is necessary to understand their full potential and ramifications before they can be used safely in the field of epidemiology, and that this application, when the day comes, it must be carried out in the hands not only of geneticists and epidemiologists but also of ecologists and even of the residents of those areas that are going to be affected.