1178 13 MARCH 2020 • VOL 367 ISSUE 6483 sciencemag.org SCIENCEPHOTO: JULIE POMERANTZ AND LUKE DOLLARNEWS | IN DEPTH
Varvara Mouchtouri of the University of
Thessaly scrutinized 114 scientific papers
and reports on screening for infections,
including Ebola, severe acute respiratory
syndrome (SARS), and pandemic influenza.
Between August 2014 and January 2016, they
found, not a single Ebola case was detected
among 300,000 passengers screened before
boarding flights in Guinea, Liberia, and Si-
erra Leone, the three countries hit hard by
the West African Ebola epidemic. Yet at least
four infected passengers slipped through
exit screening because they didn’t have
symptoms yet, and flew to their destinations.
Screening of arriving passengers did no
better. During the same epidemic, five coun-
tries asked incoming travelers about symp-
toms and possible exposure and checked for
fevers. They didn’t find cases either, but two
Ebola-infected passengers slipped through,
one in the United States and one in the
United Kingdom. (The other two flew to des-
tinations without entry screening.) During
the H1N1 flu pandemic of 2009, the research-
ers found, China and Japan intercepted
only tiny fractions of infected travelers, and
both had significant outbreaks anyway. The
duo doesn’t expect airport screening for
COVID-19 to be more effective.
Yet screening programs are costly: Canada
spent an estimated $5.7 million on a fruit-
less SARS entry screening program in 2003
and Australia spent $50,000 per detected
H1N1 case in 2009, Hadjichristodoulou
and Mouchtouri say.
It’s not entirely wasted money. By imple-
menting exit screening for Ebola, the West
African countries hit by the outbreak may
have helped head off more draconian travel
restrictions by other countries. And simply
knowing that screening is in place may de-
ter some infected or exposed people from
trying to travel.
The World Health Organization (WHO)
has detailed guidelines for countries that
do want to screen travelers. Exit screening
should start with temperature and symp-
tom checks and interviews of passengers for
potential exposure to high-risk contacts, for
instance. Symptomatic travelers should be
given further medical examination and test-
ing, and confirmed cases should be moved
to isolation and treatment. Entry screen-
ing is also an opportunity to gather contact
information—useful in case passengers be-
come infected during a flight—and to give
travelers guidance, WHO says.
But even when done well, screening
mostly serves to show governments are
doing something, says epidemiologist Ben
Cowling of the University of Hong Kong. At
best, he says, “Measures aimed at catching
infections in travelers will only delay a local
epidemic and not prevent it.” j
Madagascar’s mysterious,
murderous cats identified
Ancestors of large cats likely hopped off Arabian trading
ships more than 1000 years ago
CONSERVATION BIOLOGYO
n the trail floor that day in 2009 lay
the sprawled body of a white-furred
sifaka, a kind of lemur. “I touched
the bottom of his foot,” said Michelle
Sauther, a biological anthropologist
at the University of Colorado, Boul-
der. “It was still warm.” Then she heard a
rustle. Looking up, she caught a glimpse of
a tiger-striped feline dissolving back into the
forest—one of Madagascar’s “forest cats.”
Cats didn’t evolve on the island, and the
history of these elusive felines—twice the
size of house cats—has long been a mystery.
Now, researchers have revealed the cats’ ori-
gin story: They descend from domestic kitties
that hopped off Arabian trading ships per-
haps more than 1000 years
ago. By pinpointing them
as a separate population
that has spent centuries
adapting to Madagascar,
the work may offer a first
step toward limiting the
toll these relentless hunt-
ers take on the island’s
rich biodiversity.
With males averag-
ing more than 0.6 me-
ters long, the forest cats
have striped tabby coats,
straight tails, and a voracious appetite for
native birds, snakes, rodents, and lemurs.
They also compete with endemic carnivores
like mongooses, said Zachary Farris, a bio-
logist at Appalachian State University who was
unaffiliated with the research team.
The felines could be the feral descendants
of the domestic cat Felis catus brought to the
island several hundred years ago by Europe-
ans; if so, controlling domestic village cats
might limit the population in the forest. Or
they might be descendants of small wildcats
“that had somehow gotten over here from
mainland Africa,” Sauther says.
But Sauther’s team uncovered a different
story when it sampled DNA from the blood
of forest cats trapped using live mice or beef
parts as bait. Leslie Lyons, an expert in cat
genomics at the University of Missouri, Co-
lumbia, helped compare the forest cat ge-nomes with those of cats around the world.
The closest match: domestics from Arabian
Sea locales such as Kuwait and Oman, the
researchers reported at the end of February
in the journal Conservation Genetics. Like
other domestic cats that went wild, including
Maine coons and feral cats in Australia, the
Middle Eastern cats swelled in size in their
new home, Lyons notes.
The Arabian origin “makes sense,” said
Asia Murphy, a Ph.D. student at Pennsylva-
nia State University, University Park, who
studies the fossa, an endemic carnivore
that competes with forest cats. “Madagas-
car is a pretty special place when it comes
to cultural mixing.”
Linguistic and cultural evidence attests
to Arabic influence on the island, linked to
Indian Ocean trade routes
that stretched from Ara-
bian ports to Madagascar
starting in the second
millennium B.C.E. Cats
employed as mousers on
those ships could have de-
serted at port.
Another invasive spe-
cies supports that sce-
nario. Arabian ships also
transported Indian civ-
ets to the island around
900 C.E. for the oil pro-
duced in their anal glands, which was used
in perfumes. “Boats transporting civets
[likely] were also carrying cats,” Farris said.
More genomics work could tighten the
timeline of when the cats arrived or tell the
story of another forest cat variety, called
the fitoaty, that researchers haven’t yet
sampled. And knowing the cats aren’t just
recent runaways suggests trapping in the
forest, rather than simply neutering village
cats, might be the quickest way to control
them, Murphy said.
For Lyons, this record of Arabian Sea
cats sailing to Madagascar adds to the
global story of cat dispersal. “People think
about dogs all the time,” she says, “but
the cat has been a very silent partner in
our migration.” jJoshua Sokol is a journalist in Boston.By Joshua SokolA camera trap caught this image of a
Madagascar forest cat on its home turf.Published by AAAS