Science 13Mar2020

1178 13 MARCH 2020 • VOL 367 ISSUE 6483 sciencemag.org SCIENCE

PHOTO: JULIE POMERANTZ AND LUKE DOLLAR

NEWS | 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 BIOLOGY

O

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.” j

Joshua Sokol is a journalist in Boston.

By Joshua Sokol

A camera trap caught this image of a

Madagascar forest cat on its home turf.

Published by AAAS