Ethical dilemma: Should we get rid of mosquitoes? - Talya Hackett
Because of the pathogens they carry,
mosquitoes are responsible for more human
deaths every year than any other animal,
including other humans.
But very few of the 3,500 mosquito species
actually transmit deadly diseases
to humans.
So what if we could get rid
of the most lethal mosquitoes?
Over the last two decades,
scientists have begun conducting
experiments using engineered technologies
called “gene drives” that could
theoretically do just that.
So, should we?
To begin grappling with this question,
we have to get a sense of how
the technology works.
In the usual process of inheritance,
the genomes of each parent
recombine randomly.
So their offspring end up with the DNA
that’s a rough 50/50 mix
from their parents.
But gene drives thwart this process
and ensure they're passed on.
Gene drives are found in nature but,
using new gene-editing technology,
scientists have also begun engineering
them in contained labs.
For example, in a 2018 study,
researchers injected a gene drive
into mosquito eggs
that made females sterile when they had
two copies of the modified gene.
Such a modification would usually
disappear quickly.
But it spread.
The modified mosquitoes passed the
gene drive onto some of their offspring.
The gene drive, which they inherited
on one chromosome,
copied itself onto the other chromosome
in the offspring’s sperm and egg cells,
ensuring it was passed
on to their offspring,
regardless of which chromosome
they received.
This process repeated as all
males that carried the gene
and all females that had one copy of it,
continued reproducing,
spreading the gene drive.
As they did, they produced more females
that had two copies of the gene—
and would therefore sterile.
With a near 100% inheritance rate,
the gene spread through the population
and within 12 generations almost
all females were sterile,
and the populations crashed.
In 2020, the same team achieved
a similar result
with a gene drive that made
populations male-only.
Gene drives have proven
powerful in the lab.
So, implementing them in the wild
is a big decision—
one that’s being considered
because of how the fight
against mosquito-borne diseases is going.
Existing mosquito control measures,
like insecticide-treated bed nets,
helped reduce the number of deaths
from malaria,
the deadliest mosquito-borne disease,
between 2000 and 2019.
But fatalities have begun rising again.
Many mosquitoes have developed
insecticide resistance—
and insecticides kill more
than just mosquitoes.
In addition to the first-ever
malaria vaccine,
approved in October of 2021,
many see promise in gene drives.
Experts are researching what it would
look like to specifically target
the deadliest mosquito populations
with this technology.
Like Anopheles gambiae, for instance:
the species overwhelmingly responsible for
spreading malaria in Equatorial Africa,
which experiences the vast majority
of mosquito-related fatalities.
The idea is that,
when a gene-drive-affected population
of Anopheles gambiae drops low enough,
it would break the malaria
transmission cycle.
But before gene drive mosquitoes are
actually released into the wild,
some big questions need answers.
Like, could gene drives cross into and
cause the collapse of non-target species?
It doesn’t seem that many
mosquito species interbreed,
making this unlikely,
but scientists are conducting
research to be certain.
And how might a mosquito population’s
collapse affect ecosystems?
One team is examining the feces
and stomach contents
of insectivores in Ghana to gauge the role
of Anopheles gambiae in local food webs.
And researchers are investigating
whether suppressing populations could
make other insects more vulnerable
or leave a niche open that a harmful
species could occupy.
Scientists are also exploring alternatives
to population collapse,
like gene drives that instead
make mosquitoes resistant
to the malaria parasite.
And others are developing countermeasures
to reverse
the effects of gene drives if needed.
Meanwhile, some people have called
for gene drive research to halt
out of concern
for the possible consequences.
This raises another question: who should
decide whether to release gene drives?
It’s essential that communities,
scientists, regulators,
and governments of the countries most
affected by mosquito-borne diseases
be highly involved in the research
and decision-making processes.
Conversations are currently underway
at all levels
to establish a system to manage
this new area of research—
and the ethical questions it carries.
