ADVANCES
18 Scientific American, August 2020
T E C H
Mosquito
Rush Hour
Lidar advances help to detect
mosquito movements
During a 2016 solar eclipse, a team led
by researchers at Sweden’s Lund Universi-
ty projected a beam of infrared laser light
into the darkened Tanzanian sky to measure
how insects responded to the unusual twi-
light. Afterward, the group continued mon-
itoring for another five nights and four days.
The laser-based system used, known as
lidar, detected more than 300,000 insects
during this time.
Many of these bugs were the world’s
deadliest: the mosquito, one genus of which
can carry the parasite that causes half a mil-
lion malaria deaths every year. During the
mosquitoes’ morning and evening “rush
hour,” the researchers measured high num-
bers of the insects taking flight at nearly the
exact same times each day. The eclipse, they
found, also summoned a large cloud of mos-
quitoes. The result suggests that in nature,
light levels, rather than circadian rhythms,
dictate mosquitoes’ activity. Crucially, the
study, published in May in Science Advances,
also illustrates lidar’s potential to assess
malaria risk and prevention measures—and
to help collect entomological data.
The study marks “the first time that
you can classify multiple different types of
insects over the field in their natural set-
tings,” says lead author and Lund physicist
Mikkel Brydegaard.
The study tested an entomological lidar
type Brydegaard invented, which is used
around the world. In his system, each
insect flying through a lidar beam reflects
light back into a telescope. The light, called
backscatter, can be analyzed to find the fre-
quency of wingbeats, which lets research-
ers determine the numbers and species of
insects passing through. The team wasable to identify mosquitoes, moths, flies
and midges—and could even differentiate
between male and female mosquitoes.
Scientists fighting malaria often use
physical traps to catch mosquitoes at vari-
ous life stages, then analyze them and
their genes in a laboratory. But this meth-
od is time-consuming and expensive, and
it does not let scientists assess populations
over time or evaluate the efficacy of spray-
ing or other control measures in the field.
“With this type of lidar, they’re demon-
strating with the eclipse and in general that
you can actually track the population with
much higher accuracy,” says New Jersey
Institute of Technology physicist Benjamin
Thomas, who was not involved in the study
but is among a growing number of ento-
mology researchers experimenting with
lidar. “You can observe thousands and thou-
sands of insects, finally opening the door to
us being able to monitor those populations.”
The scientists say lidar installations
could raise malaria risk alerts, as a weather
station can warn of impending storms.
And tracking mosquitoes is just one appli-
cation of the technology; it could also be
used to detect pollinator diversity and
monitor pests on farms or in protected
areas, Brydegaard says. — Susan CosierMEDICINE
Snakebite Pill
A preexisting drug could buy
time for treatment
A drug that treats poisoning from heavy
metals may also offer a fighting chance at
surviving a venomous snakebite. In a study
published in May in Science Translational
Medicine, researchers show that oral doses
of the medication can reduce viper ven-
om’s effects in mice.
Saw-scaled or carpet vipers are a group
of aggressive venomous snake species
found in Asia and Africa, including some
densely populated regions with limited
access to modern medical facilities. “They
arguably cause more bites and deaths than
any other snake in the world,” says Abdul-
razaq Habib, an infectious and tropical dis-
ease physician at Nigeria’s Bayero Univer-
sity Kano, who was not involved in the
study. The vipers’ venom destroys tissue
around the bite site and sometimes leads
to loss of digits, limbs or lives, Habib adds.
This venom contains toxic enzymes
called metalloproteinases, which rely on
zinc ions to function and can cause tissue
damage and internal bleeding. “We hypoth-
esized that capturing these ions may inhibit
the toxin’s activity and neutralize its harmful
effects,” says Laura-Oana Albulescu, a bio-
chemist at the Liverpool School of Tropical
Medicine (LSTM) in England and lead
author on the new study. She and her
col leagues investigated treatments for poi-
soning from heavy metals that use com-
pounds to clamp onto loose metal ions.
“We hope our study will highlight the prom-
ise of repurposing oral treatments as first-
line interventions for snakebite—an idea
that has been tinkered with before ... but
was never fully developed,” Albulescu says.
The researchers’ laboratory tests
showed that a family of three promising
drugs could inhibit the toxin’s activity in
venoms from multiple species of saw-
scaled vipers. Next they tested each drugin mice injected with a typically lethal dose
of venom from a West African carpet viper.
One drug, unithiol, saved all mice when
given 15 minutes after venom injection and
followed an hour after injection by an anti-
venom dose. Neither the drug nor antiven-
om alone was sufficient to save all the
envenomated mice, Albulescu says. The
results suggest unithiol might work as an
early snakebite intervention, buying more
time to reach a hospital for treatment.
“The findings reported are very promising,
and the investigators have explored differ-
ent practical scenarios,” Habib says.
The drug costs much less than antiven-
om and is already designated safe for other
uses, says Nicholas Casewell, a study co-
author and venom expert at LSTM. The
researchers plan to begin clinical trials in
humans early next year to verify the drug’s
safety and tolerability in African popula-
tions, who bear the brunt of viper attacks.
Their hope is that within a couple of years
unithiol might become the world’s first
“snakebite pill.” — Harini Barath© 2020 Scientific American