Malaria is one of the oldest diseases in human history, dating back to ancient civilizations
in Greece and China.
It has even been attributed to aiding the fall of the Roman Empire.
So if we’ve been fighting malaria for so long, why haven’t we been able to stop it?
The name “malaria” comes from “mal aria” or "bad air," because early interpretations of
the disease came before we could connect the undesirable symptoms of malaria with a mosquito
bite. And later with a tricky little parasite known as Plasmodium falciparum.
My name is Karine Le Roch.
I'm a professor at the University of California Riverside in the department of molecular,
cell, and systems biology.
And my lab is working on the human malaria parasite.
So, trying to identify a new way to combat the disease.
I always find that the parasite are extremely clever.
Not to mention impressive, taking down the Roman Empire is pretty big feat for a tiny parasite.
But it had a bit of help from its notorious host, the mosquito.
Though not every mosquito has the ability to carry or spread the malaria parasite.
There is only a very small percentage of mosquitoes that can get infected and can transmit the disease.
These mosquitoes are anopheles and only a small proportion are anopheles and only female
because mosquitoes are usually vegetarian.
And the reason they stop being vegetarian is that females need the proteins in blood
to produce and lay eggs. So an infected mosquito bites a human, it injects sporozoites, these
sporozoites are going to be injected to the blood and reach the liver.
The parasite wants to get into a cell fast to avoid the patrolling immune cells.
It heads to the liver first, wrapping itself in an invisibility cloak of sorts -
the liver cell membrane.
Since our body doesn’t yet know the parasite is there, there won’t be any resulting symptoms.
The parasite replicates in the liver cells until it bursts out, setting its sights now
on the red blood cells.
These red blood cells are another good place to take shelter from the immune system and
are perfectly suited to the parasite’s need to replicate.
As soon as the parasite is inside, it starts to drastically alter the makeup of the cell.
When they get inside the red blood cell, they will take some time to maybe feel comfortable,
to settle down, and then they will start their differentiation and reproduction processes.
As it replicates, the parasite will snack on hemoglobin in the red blood cells and,
by this point, the human immune system knows that something sketchy is going on.
For one thing, this red blood cell looks nothing like it used to - it’s stiffer, stickier,
and is no longer smooth on the outside.
So as soon as the parasite gets in, the host immune system realize that the red blood cells
are transformed and that there is strange things going on inside and the host immune
system is going to try to directly target the infected red blood cells.
When a red blood cell is infected, the immune system will recognize it based on the parasite
proteins exported on the outside and destroy it, but in this case the parasite has found
a way to escape this by repeatedly changing the proteins it expresses.
It becomes, essentially, a cat and mouse game where the immune system simply can’t keep up.
As soon as it knows what to destroy, the parasite puts on a new protein mask on its host cell and
gets away unscathed.
While its evading detection it uses human cells to replicate and eventually differentiate
into male and female versions of itself, something that can only happen in the human host.
Then it needs to be picked back up by a mosquito in order for those versions to reproduce,
which can only happen in the mosquito host.
This cycle...
I mean you really need an infected human to infect mosquitoes and you need an infected
mosquito to infect a human.
And as if that weren’t enough, when the red blood cells burst, they release toxins
into the blood.
The major symptoms of malaria; a nasty fever, chills, headache, vomiting, are caused in
part by these toxins.
These can actually cause the patient to get into coma and and stop the oxygen exchange
between your blood and your brain.
So how do you treat or vaccinate against a parasite that is constantly on the move and
changing what it looks like?
So that's that's a big issue.
A lot of money and research lab are working on trying to define a vaccine against malaria.
Right now we have a vaccine that can protect 30 to 40 percent against the strongest side
effect of the disease but it's not protection as we are familiar with.
The goal of my lab is really to try to stop the parasite in its intensive replication
steps or to make sure we just inhibit replication and division of the parasite inside the human host.
And as we come up with new treatments, the parasite itself is always evolving and evading
us in new ways.
In order to eradicate the disease we really have to become more clever than they are.
The CDC, center for controlled disease, was actually built to fight malaria and we've
been they've been they have developed an eradication campaign that have been extremely successful
after the second World War where malaria was eradicated from the US and Europe.
The success was really intense because of the use of DDT to actually kill mosquitoes.
Of course, dumping DDT on 6 million homes isn’t really a viable solution these days
so we’re going to need to find to find a better weapon to combat the disease.