By Evelyn Lee
December 1, 2022
UPDATED 12:00 PM EST
[Photo Credit: News-Medical.net]
Recently, there has been a breakthrough in the genetic modification of living animals, where the vector for the world's deadliest disease, malaria, has been modified to pass down a gene that codes for antimalarial properties. Malaria, which is a disease that is passed from mosquitoes through a gut plasmodium parasite within the vector (hence, the reason why not all mosquito bites lead to malaria, since it’s the parasite that’s actually causing the illness), is extremely rare in the more developed world, like the US or Australia, but is more common in lower-income countries located in places like South Asia and Africa. Malaria has been around for as long humans have been around, and it’s gotten to the point where some people have begun adapting against this blood-borne illness. For instance, some people, especially of African-descent, have something called a ‘sickle-cell trait’ that codes for malaria-resistant blood (although two copies of this gene may result in sickle cell anemia.)
Recent studies have found that by using CRISPR-Cas9, researchers were able to genetically modify mosquitoes to become more resistant to plasmodium parasites, which would prevent further spread of malaria. By using CRISPR-Cas9, the researchers inserted the antimalarial protein into the same section of genes that activate after a mosquito finishes a blood meal, that could then be passed down to the mosquito’s offspring. This concept is called a ‘gene drive,’ which artificially causes a population of organisms, whether it be mosquitoes, rats, or other disease vectors, to be more in favor of a certain trait. Although it’s still debated on whether or not these genetically-modified organisms will cause any negative effects on their environment once released into the wild, this method is more ethically conscious than other efforts. For instance, there was debate amongst scientists on whether or not the artificial sterilization of adult mosquitoes would be immoral or not. A hormone analogue called pyriproxyfen, or PPF, has been shown to sterilize adult mosquitoes on contact (or prevent juveniles from undergoing metamorphosis). However, there’s ethical concern over whether or not humans have the moral high-ground to eliminate an entire species, not to mention the countless other organisms that rely on mosquitoes as a food source and would most likely also decrease in population, causing many ecosystems to destabilize.
Although this research is still tentative, there’s a lot of promise behind it. Mosquitoes not only have the capability to spread malaria, but can also spread the Zika virus, West Nile virus, dengue, various kinds of encephalitis, or the inflammation of the brain, and etc. According to the CDC, almost half of the world’s population lives in areas at risk for malaria infections, so the potential this research has is immense.
“How Sickle Cell Protects Against Malaria.” Understanding Animal Research, www.understandinganimalresearch.org.uk/news/how-sickle-cell-protects-against-malaria-a-sticky-connection.
Lwetoijera DW, Harris C, Kiware SS, Killeen GF, Dongus S, Devine GJ, Majambere S. Comprehensive sterilization of malaria vectors using pyriproxyfen: a step closer to malaria elimination. Am J Trop Med Hyg. 2014 May;90(5):852-5. doi: 10.4269/ajtmh.13-0550. Epub 2014 Mar 17. PMID: 24639296; PMCID: PMC4015577.
“Simple Genetic Modification Aims to Stop Mosquitoes Spreading Malaria.” eLife, 13 Apr. 2021, elifesciences.org/for-the-press/042e019f/simple-genetic-modification-aims-to-stop-mosquitoes-spreading-malaria.