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What if you could use genetic engineering to stop humanity's most
dangerous predator, the deadliest animal on the planet responsible for the death
of billions, the mighty mosquito? Along with other diseases it plays host to
Malaria, one of the cruelest parasites on Earth
possibly the single biggest killer of humans in history.
In 2015 alone
hundreds of millions were infected and almost half a million people died.
A new technology could help us eradicate Malaria forever, but to do so we need to
engineer a whole animal population.
This is not a hypothetical problem, the modified mosquitoes already exist in a lab.
Should we use the technology, and is malaria bad enough to risk it?
(Intro Music)
Malaria is caused by a group of microorganisms: Plasmodia, very weird
microorganisms that consists of just a single-cell, they're parasites that
completely rely on mosquitoes. Malaria always starts with an insect bite.
In it's salivary glands, thousands of sporozoites wait until the insect penetrates your
skin, immediately after invading you they head for the liver where they quietly
enter big cells and hide from the immune system. For up to a month they stay here
in stealth mode consuming the cells alive and changing into their next form:
small drop like merozoites, they multiply generating thousands of themselves and
then burst out of the cells. So thousands of parasites head into the bloodstream
to look for their next victims, Red blood cells, to stay unnoticed, they wrap
themselves in the membranes of the cells they killed. Imagine that! Killing someone
from the inside and then taking their skin as camouflage, brutal!
They now violently attack red blood cells, multiplying inside them until they burst
then finding more red blood cells and this cycle repeats over and over.
Pieces of dead cells spread lots of toxic waste material, which activates a powerful
immune response causing flu-like symptoms, among the symptoms are high
fever, sweats and chills, convulsions, headaches and sometimes vomiting and
diarrhea. If malaria breaches the blood-brain barrier it can cause coma,
neurological damage or death. The parasites are ready for evacuation now.
When another mosquito bites the infected human they get a ride, the cycle can
start over.
In 2015, the Zika virus, which causes horrible birth defects if it
infects pregnant women, spread rapidly into new areas around the globe. It too
is carried by a mosquito. The mosquito is the perfect carrier for human diseases
they've been around for at least 200 million years. There are trillions of
them and a single one can lay up to 300 eggs at a time. They are practically
impossible to eradicate and the perfect parasite taxi. But today we have a new
revolutionary technology, that could enable us to finally win the war
against them; CRISPR. For the first time in human history, we have the tools to
make fast, large-scale changes to entire species, changing their genetic
information as we please.
So instead of attacking isolated groups of insects, why not just change the
types that transmit diseases?
Using genetic engineering, scientists
successfully created a strain of mosquitoes that are immune to the
malaria parasite by adding a new antibody gene that specifically targets
plasmodium. These mosquitoes will never spread malaria. But just changing genetic
information is not enough. The edits would only be inherited by half the
offspring because most genes have two versions inside the genome as a
fail-safe. So after just two generations, at most only half of the offspring would
carry the engineered gene. In a population of billions of mosquitoes they would
hardly make a difference.
A genetic engineering method called the gene drive
solves this problem.
It forces the new gene to become dominant in the following generations
overpowering the old gene almost completely.
Thanks to this twist, 99.5% of all the engineered mosquitoes offspring will
carry the anti-malaria edit. If we were to release enough engineered mosquitoes
into the wild to mate with normal mosquitoes, the malaria blocking gene would spread
extremely quickly.
As the new gene becomes a permanent feature of the
mosquito population, Plasmodium would lose its home base.
Scientists hope that the change would be so fast that they could not adapt to it quickly enough.
Malaria could virtually disappear.
If you take into account that
maybe half a million children are killed by it every year, about five have died
since this video started. Some scientists argue that we should use the technology
sooner, rather than later.
The mosquitoes themselves would probably only profit from this, they don't have
anything to gain from carrying parasites and this might only be the first step
Malaria might just be the beginning.
Different mosquitoes also carry Dengue
fever and Zika, ticks transmit Lyme disease, flies transmit sleeping sickness
fleas transmit the plague. We could save millions of lives and prevent suffering
on an unbelievable scale. So, why haven't we done this yet?
For one, CRISPR editing is
barely four years old, so until very recently we just couldn't do it as fast
and easily. And there are valid concerns.
Never before have humans consciously changed the genetic code of a free-living
organism on this scale.
Once we do it,
there is no going back. So it has to be done right, because there could be
unwanted consequences if we set out to edit nature.
In this specific case of malaria though, the risk might be acceptable
since the genetic modification doesn't make a big change in the overall genome.
It only changes a very specific part.
The worst-case scenario here, is probably
that it might not work or that the parasite adapts in a negative way.
There is still much debate.
Technology as powerful as gene drive, needs to be
handled with a lot of care but at some point we have to ask ourselves: Is it
unethical to not use this technology, when every day 1,000 children die.
Humanity has to decide how to act on this in the next few years.
The public discussion is way behind the technology in this case.
What do you think?
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do so here. We really appreciate it. If you want to learn more about the topic
of genetic engineering, we have another video about CRISPR and GMOs, and in case
that's too much biology for you, here's a space playlist.