Mosquitoes belong to the Order Diptera of Class Insecta
Up to what extremes are we willing to take in order to ensure the survival of our species? Mosquitoes may be tiny and insignificant. But, they are one of the deadliest ectoparasites that ever lived. They do not just feed on our blood. They could even leave us with a gift – like a “Pandora’s box” of dreadful diseases. Thus, we took a long stride. We armed ourselves with various weapons against these obnoxious flying “blood–suckers“. And recently, researchers from Imperial College London came up with a novel strategy aimed at destroying them at their molecular level — by hacking their DNA with CRISPR technology.
Mosquitoes are winged insects that belong to the Order Diptera. Their name means “little fly“. They have slender bodies, a pair of wings, three pairs of legs, a proboscis, and a pair of feathery antennae. Their life stages include egg, larva, pupa, and adult. Gravid female lays eggs on the water surface. Larvae hatch from the eggs and grow into pupae. Pupae, also called wrigglers, develop further and then emerge from the water as adults. Adult males feed on nectar whereas adult females feed on blood. The females have specialized proboscis that they use to puncture the skin of their host and to suck blood.
Female mosquitoes feed on the blood because they need nutrients from the blood when they produce eggs. Blood does not coagulate in their proboscis because of the presence of anticoagulants in their saliva. They inject saliva into the skin of the host. Inopportunely, the saliva also serves as the main route by which mosquitoes introduce pathogens into the host’s bloodstream. Some of the mosquito-borne diseases include yellow fever, dengue fever, chikungunya, malaria, lymphatic filariasis, tularemia, and Zika disease.
CRISPR, the game changer
Scientists from Imperial College London had a breakthrough when they used CRISPR technology for a gene drive to completely wipe out a population of mosquitoes grown inside the lab.1
Short for clustered regularly interspaced short palindromic repeats, CRISPR is a gene-editing tool that scientists use to splice specific DNA targets and then replace them with a DNA that would yield the desired outcome.2
The researchers used CRISPR–Cas9 gene drive to suppress the population of caged Anopheles gambiae mosquitoes (human malarial vector). They modified the gene responsible for determining sex in male mosquitoes and turned the male gene dominant. Then, they added these “hacked’ mosquitoes to a caged population of unaltered male and female mosquitoes. The next generations of females could no longer lay eggs and could not bite. And by the eight generation, the population had no longer had females.3
Wiping out mosquitoes
Not all species of mosquitoes act as our straight foes. Thousands of mosquito species do not serve as vectors of diseases. Only a few hundreds (about 200) of them transmit human pathogens (e.g. Aedes aegypti, Anopheles spp.). Unfortunately, these few hundreds carry viruses, bacteria, protozoans, and helminthes that can cause serious, even fatal, diseases. Furthermore, current methods to eradicate them, e.g. spraying or fogging using insecticides, proved less ineffective since they developed resistance to such insecticides. Thus, the CRISPR technology could prove useful in this regard. However, the question remains: What will happen when these mosquitoes are completely eradicated from the face of the earth?
Obviously, humans reap directly the benefit of eradicating mosquito-borne diseases. However, it might also lead to an irrevocable ecological impact we could regret. Particularly in the food chain, loss of certain mosquito species could lead to the insufficiency of food for insectivores, such as birds and fish. And over time, humans might eventually suffer as well from this jarring food-chain disturbance.
Mosquitoes have lived for so many million years. Do we have the right intent and purpose to deny them the right to live side by side with us? Could it be that we are in the verge of desperation? Definitely, we possess a powerful tool in our hands by the advent of CRISPR technology. However, what good of a purpose would it be if we use it solely for our own good?
— written by Maria Victoria Gonzaga
1 Kyrou, K., Hammond, A. M., Galizi, R., Kranjc, N., Burt, A., Beaghton, A.K., Nolan, T. & Crisanti, A. (2018). A CRISPR–Cas9 gene drive targeting doublesex causes complete population suppression in caged Anopheles gambiae mosquitoes. Nature Biotechnology. Retrieved from this LINK
2 Gonzaga, M. V. (2018). CRISPR caused gene damage? Rise and pitfall of the gene-editor. biologyonline.com. Retrieved from this
3 Houser, K. (2018 Sept. 25). SCIENTISTS WIPED OUT A MOSQUITO POPULATION BY HACKING THEIR DNA WITH CRISPR. Futurism.com. Retrieved from this LINK