Do mosquitos actually bite some people more than others? - Maria Elena De Obaldia
Some swear they’re cursed to be hunted
by mosquitoes
while their close-by companions
are regularly left unscathed.
But is this an illusion?
If it's not, what's going on?
And what can we do about it?
It all comes down to how— and why—
mosquitoes find us.
While male mosquitoes stick
to nectar for sustenance,
females also seek out blood to provide
the nutrients they need for their eggs.
Different mosquito species evolved
to feed on different animals.
And, probably within the last
10,000 years,
multiple mosquito lineages independently
evolved a predilection for people.
As human settlements became
more permanent,
they provided plenty of standing water,
even through intense dry seasons,
which supported mosquito
reproduction year-round.
Female mosquitoes are equipped with
antennae covered in hair-like appendages
that contain odor-sensing
receptors and neurons.
These pick up on the signals
of their preferred hosts,
And over thousands of years,
the mosquitoes that target humans have
gotten extremely good at tracking us down.
They also target parts of our bodies
where we’re less likely to notice them.
And they’re sensitive to visual
cues and changes in airflow,
so when we try to defend ourselves,
they can make swift escapes.
They even learn to avoid particularly
defensive people altogether.
But before these close encounters happen,
several factors alert mosquitoes
to people's presence.
Female mosquitoes can pick up on the
carbon dioxide humans constantly exhale
from about 10 meters away.
Once they’ve gotten the CO2 cue,
they become especially interested
in dark, high-contrast objects
and the hues found in human skin.
As they follow the carbon dioxide plume
to its source,
they eventually sense body heat and odors.
These smells are generated by the many
microorganisms that live on our skin.
They break down the secretions our bodies
produce, like sweat and sebum.
In doing so, our skin microbes create
smaller organic compounds
that can vaporize
and get picked up as smells—
smells that human-homing mosquitoes
are especially attuned to.
Getting extra sweaty can temporarily make
people more attractive to mosquitoes—
as can ingesting alcohol
or being pregnant.
And the Plasmodium parasite
that causes malaria
makes the people it infects more appealing
to mosquitoes by increasing
the amounts of certain fruit-smelling
aldehyde compounds on their skin.
This is extremely helpful to the parasite
because it depends on both humans
and mosquitoes to reproduce.
But in addition to these
temporary factors,
about 20% of people are thought to be
naturally high attractors,
or mosquito magnets,
who are disproportionately targeted
year after year.
If you’re one of them,
you’re probably well aware.
Sorry about that.
Why this is seems to come down to some
skin-specific characteristics.
While carbon dioxide exhalations and
body heat consistently signal the presence
of warm-blooded animals,
human body odor is more distinctive.
And everyone hosts different microbial
communities on their skin,
which contribute to unique body odors
that likewise vary from person to person.
Researchers reveal that the receptors
mosquitoes use to detect acidic compounds
are especially important in helping
them navigate towards humans.
And, indeed, humans with more abundant
skin acids
prove to be consistently more attractive
to mosquitoes.
Because it’s such a persistent trait,
certain genes may play a role,
perhaps by helping determine
the skin’s microbial composition.
Scientists have observed that mosquitoes
demonstrate similar levels of attraction
among identical twins while responding
more variably to fraternal twins,
which supports that there may be
some genetic basis at play.
But beyond confirming that mosquitoes
are, in fact,
conspiring against some
of us specifically,
understanding what makes people
mosquito-magnets
has serious, large-scale implications.
Every year, hundreds of thousands of
people die from mosquito-borne diseases.
And resources aren’t reaching
those who need them most.
This knowledge can help inspire solutions,
like more effective insect repellents
that manipulate the skin's
microbiome and odors.
And knowing that some people are
especially strong mosquito attractors
could also help efforts
to get them resources
like repellents, bed nets, vaccines,
tests, and treatments.
The results could not only be less itchy,
they could break transmission cycles
and save countless lives.
