Malaria. A lethal disease that kills millions every year, the largest killer of children. Mosquito, or in the malaria-carrying case, anopheles stephensi.
Not only one, but the number one carrier of malaria. So the question is how to prevent the immense amounts of unneeded suffering, especially when every year 300-600 million are infected. Well, two technologies by the name of CRISPR and gene drive just might have finally found the final solution to this puzzle. First, or in order to fully understand the problem and solution at hand, we need to see what malaria is and what mosquitoes have to do with it. So, malaria. It all starts off with the mosquito, or more specifically the parasites that lie within.
A type of single-celled organism, and a type of parasite that is called plasmodia. This sporozite makes itself a temporary home in the mosquito’s salivary glands, just waiting for the time when the mosquito takes a bite. Malaria always starts off as an insect bite. While mosquito is biting you, the sporozoites enter your bloodstream. From there they immediately go to the liver, where they hide from the immune system in cells.
Then they multiply, turning into merozoites (all inside the liver cell), and consume the cell alive. Finally, they burst out of the cell, killing it. And then they do something even worse. They cover themselves with the “corpse” of the dead cell to hide from the immune system as they begin there final, and lethal act. They enter the bloodstream yet again and invade the red blood cells.
As the invading is happening they multiply within the red blood cells, kill it and then move onto the next. All of this repeats itself over and over again until it reaches the blood-brain barrier. If the merozoites proceed into the brain you may suffer neurological damage, coma, and at worst death. So, in conclusion, we don’t need to get rid of the mosquitoes, but instead get rid of their capability to temporarily harbour the plasmodia. And this is where CRISPR and gene drive come into play.
However, the combination of CRISPR and gene drive is something that scientists are looking forward to in the future, but haven’t yet affected the mosquitoes of the wild. Currently, malaria is being treated and prevented very differently and has quite a dark side to it. Nowadays when people travel in places with a high risk of malaria they take antimalarials, such as atovaquone plus proguanil, but such drugs only work for some strains of malaria, and may have quite extreme side effects. Antimalarials such as mefloquine, used in the Canadian army according to cbc.ca, has side effects that are not only extreme while taking it, but its effects last long after, even years after one has taken the drug. These side-effects include but are not limited to: panic attacks, hallucinations, dizziness, vivid dream, insomnia etc. There also is no current vaccine for malaria.
So, clearly, these meds might partially work, but don’t prove to be the best solution to the problem at hand.Now, the exciting part. What is CRISPR and gene drive and how can we use it to aid us in our fight against malaria? Well, let’s start with CRISPR. CRISPR stands for clustered regularly interspaced short palindromic repeats.
These repeats came from the original CRISPR, found in an ancient bacteria, used for defence against viruses trying to invade it. There is a certain enzyme in these bacteria call Cas9. Now, when the viruses try to invade the bacteria, the first time the bacteria are helpless and most of the time they die, but if by some miracle they don’t, they incorporate some of the viruses DNA into their own, making them immune to further attacks.
Cas9 is the enzyme that goes along and finds a certain part of the DNA and cuts it out. If we want to use this to change a certain part of the DNA, scientists create something called a guide RNA, which essentially is combined with the Cas9. Once it is combined the guide RNA tells the Cas9 where to stop and then Cas9 begins to cut the DNA. When the DNA is cut, it is replaced with the RNA and put back together with the cells natural healing system. But there is a catch, this modification is only valid for the certain mosquito that the CRISPR edits, and this is where gene drive comes into play. When CRISPR comes to cut the DNA and replace it with the RNA, the RNA is equipped with its own CRISPR, and this RNA equipped with CRISPR is what scientists call gene drive.
That way when two genes meet during sexual reproduction, the CRISPR of the modified gene starts cutting the wild gene. The cell of the damaged DNA uses the other (modified) DNA as an example for rebuilding the DNA, and thus you are left with two exact copies of the gene. This creates a modified organism, which then will go on to mate with the next, and their offspring will do the same. This means that soon the wild population will be wiped out and the modified population will take over. We can use this in the case of mosquitoes, cutting out their “malaria-carrying” gene and replace it with a gene drive and a piece of RNA that doesn’t have the capability to carry malaria.
Gene drive sounds like a miracle! Why aren’t we using it now, especially when so many lives are at stake? Well, it is true that these mosquitoes do exist, but just in laboratories. Scientists have never genetically altered a whole entire population, and are still sceptical about releasing these mosquitoes into the wild. The biggest concern is that it will only take a few modified mosquitoes to change the whole species of that mosquito.
It would be a very aggressive approach, to say the least. Another concern would be that if these mosquitoes are released into the wild of one country, other countries and even continents will have to participate, whether they like it or not, due to the wildfire-like spread of these modified mosquitoes. But overall the risks aren’t that plentiful, and some scientists say that the biggest risk would be that it just doesn’t work, and we are left with a bunch of mosquitoes just like how we started. The immense good it would do for the world, and for the millions of people suffering from malaria.
To put it in perspective It would take the average adult approximately 4 minutes to read this essay (at 300 words per minute) and one child dies of malaria every 30 seconds, so if one does the math that would mean that 8 children died while someone was reading this essay. If that doesn’t make a person convinced of just giving the CRISPR-gene drive pair a shot, what will?In conclusion, malaria is a deadly disease, and there is a way to help prevent it. There are also many other things scientists can do with this technology if it proves to be successful. For example, they could engineer ticks so that they don’t carry Lyme disease, or fleas to stop carrying the plague. These would all be drastic changes to the world, but it’s most likely that we can all agree the world would do good with even a bit of change. And as Jimmy Dean said, “I can not change the direction of the wind, but I can adjust my sails to always reach my destination.”