Malaria might be making a comeback soon.
You know, the leading killer of children
under 5 years old in parts of Africa
and that nearly half of humanity is still at risk for?
Yeah Malaria is serious stuff.
And don’t get me wrong.
We’ve been taking it seriously for decades.
Bed nets and insecticides have saved many lives.
But progress has stalled as the mosquitoes
that spread malaria have adapted their own tool set.
They’re developing a resistance to our insecticides.
Which means we’re going to need some new ways
to prevent this disease.
Here’s how scientists are fighting
the latest generation of super mosquitoes.
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Malaria continues to be widespread,
but it’s not for lack of trying to kick the disease’s butt.
Nets and insecticides, among other interventions,
have made incredible progress over the years.
The World Health Organization reports
that annual deaths from malaria
went from about 897,000 in 2000 to 568,000 in 2019.
But since then,
the numbers have actually gone up.
And it’s not like we stopped using the nets and insecticides.
They just don’t have the same effect they used to.
We haven’t changed.
The mosquitoes have.
Malaria’s version of “it’s not you, it’s me.”
The mosquitoes that infect us with the parasite
that causes malaria are developing resistance to almost all insecticides.
And that includes common ones like pyrethroids,
AKA what most malaria control depends on.
This doesn’t mean we need to stop using insecticides altogether,
because they still work to an extent.
But it’s a lesser extent than it used to be.
Some mosquitoes are getting really good
at fighting off these toxins.
In one study,
only 3.8% of the insects died after exposure to pyrethroids.
And if you’re wondering,
here’s how they manage to pull that off:
There’s a certain family of enzymes called cytochromes
that help detoxify stuff.
Those enzymes may be partially to blame
for the rise of the mosquito resistance.
In particular, the group of enzymes
called cytochrome P450 monooxygenases,
or P450s for short,
seem to operate differently in mosquitoes
that show insecticide resistance.
The difference means the mosquitoes
can fight off insecticides pretty well.
Now, we usually have no beef with P450s,
because they help almost all living things break down toxins,
including us!
But when our friend starts helping our enemy too,
that’s when we take issue with it.
And that’s led us to a few ideas for dealing with this problem.
Since the insecticide-resistant mosquitoes
with different P450 enzymes aren’t yet resistant to all insecticides,
we can still rely on the few
that they’re not currently resistant to.
For example,
the synthetic insecticide Actellic remains fairly effective.
But what we don’t want to do is let mosquitoes develop resistance to
that too and end up in the exact same place a few years from now.
To keep that from happening, there are management techniques
like rotating different insecticides to keep things fresh.
Instead of relying on Actellic for an extended period of time,
we could regularly swap it out for other insecticides
so the mosquitoes in a particular area don’t become familiar enough
with any one toxin to develop resistance.
So that’s one way forward.
But an interesting new option is a chemical called piperonyl butoxide,
or PBO.
It’s not an insecticide at all,
but it prevents P450s from doing their job.
As the mosquitoes break down the PBO,
bits and pieces of the molecule bind to the P450 enzymes,
blocking them from detoxifying insecticides.
Sprayed in combination with pyrethroids,
it brings the super mosquitoes back to square one
where they’re vulnerable again.
In a recent study in Ghana,
this combo showed encouraging results.
Depending on where the sample group of mosquitoes was collected from,
the PBO and pyrethroids
were anywhere from 43.8% to 100% effective.
So we have some really promising avenues
for continued insecticide use,
even in the face of insecticide-resistant mosquitoes.
And they might lead us back in the direction
we were headed before: the eventual complete elimination of malaria.
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