Bats transmit Ebola directly to humans

Scientific bulletin n°316 - April 2009
Bats transmit Ebola directly to humans
© IRD / Éric Leroy
© IRD / Alain Epelboin
Bats are suspected
of being a natural
reservoir of Ebola
virus. They can
contaminate humans
directly, without
the intermediary of
a secondary host
such as great apes.
IRD researchers
and their partners1
recently found a
strong correlation
between the annual
migrations of fruit
bats and the 2007
Ebola fever epidemic in the Democratic Republic of the
Congo (DRC) which
killed nearly 200
people.
Their investigations
retraced the sequence of events that
could have led to
this epidemic. They
discovered how all
the conditions coincided to enable the
virus to spread in
humans.
Ebola, which induces haemorrhagic
fever, has been raging for 30 years in
Africa. Since 2001,
several epidemics
have broken out in
DRC, hitting both
humans and great
apes. This survey
points the way to
better prediction of
future epidemics.
The researchers interviewed people living in the agglomeration of Kampungu, at the epicentre of the 2007
Ebola epidemic that raged in the Democratic Republic of Congo. That year the villagers noted a particularly
massive annual migration of bats (here Hypsignathus monstrosus).
IRD researchers and their partners1
have determined the source of the
Ebola epidemic that broke out in
the Democratic Republic of Congo
(DRC) from May to November 2007.
They first retraced the itinerary of the
virus by conducting epidemiological
surveys over the area affected by the
epidemic. Enquiries carried out by
Congolese and international teams had
previously identified the person from
whom the epidemic had started: a 55
year-old woman living in Ndongo, one
of ten villages of the agglomeration of
Kampungu2, at the epidemic epicentre.
About 25 June, she developed haemorrhagic fever typical of Ebola (severe fever, sickness, diarrhoea, haemorrhages) and died one week later.
The people who had taken care of her
succumbed only days afterwards from
haemorrhagic fever. The epidemic had
begun.
But how did this person catch the disease? She had had no contact with
any dead animal or anyone ill with the
disease. In order to find out, the research team’s investigations were extended to different districts of the Kampungu agglomeration. Proceeding from
village to village, they reconstructed
the chain of events that led to infection
of the woman who was the eventual
source of the epidemic.
All the outbreak conditions were
present. At the end of April, a man from
another village went regularly to the
weekly market of Mombo Munene to
buy fresh fruit bats. These chiropterans
flood the markets every year, at the time
of their great migration, as they constitute an important protein source for
people. Repeated contact with the animals’ blood when buying them induced
mild symptoms in the man, which probably went unnoticed. He would therefore have developed only a low viral
load, as many other people frequenting
the same markets probably had. This
man had a 4 year old daughter whom he
regularly took to the market in May with
his wife to the village set in the bush3,
3 or 4 hours’ walk. The child would have
caught the virus during the long journeys in her father’s arms4. She fell ill
some days afterwards and died shortly
afterwards. According to custom, the
child’s body was washed for the funeral ceremony, by a close friend of the
family. It was the woman from Ndongo.
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You can find the IRD photos concerning this bulletin, copyright free for the press, on www.ird.fr/indigo
chers brought the first evidence for
a direct link between the chiropterans and the onset of an Ebola epidemic. Their investigation helps understand better how an epidemic can
flare up in humans and consequently
gives pointers as to the appropriate
preventive measures to take in villages
located under the bats’ migration path.
*See Scientific bulletin n°231 - Fruit
bats a reservoir for Ebola virus
Gaëlle Courcoux – DIC
Translation - Nicholas Flay
1. This study was conducted jointly with
research scientists from the Muséum National d’Histoire Naturelle in Paris, the Ministry of Health of the Democratic Republic
of Congo (DRC), the Institut National de
Recherche Bio-médicale of Kinshasa and
World Health Organization (WHO).
2. The villages of the agglomeration of
Kampungu are situated along the road
linking Mweka to Luebo, in the province
of Kasaï Occidental, in the centre of the
country.
3. Each village of the area has two districts: the village along the main road and
its “twin” village set back in the bush. In the
1960s and 1970s, the DRC authorities ordered the isolated villages to move closer
to the main lines of communication to facilitate the populations’ access to medical
centres, education, administrative services,
etc. Now the village in the forest area supplies
its twin with farm produce or animals obtained
by hunting like bats.
4. Recent studies detected the presence of Ebola virus in the body fluids like saliva or sweat.
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© IRD/ J-J Lemasson
Scientific bulletin n°316 - Avril 2009
Nobody else among the little girl’s family or friends had been contaminated. The girl was probably not ill long
CONTACT :
enough to build up a high viral load,
ÉRIC LEROY
and only prolonged contact with her
Unité mixte de recherche
body could have led to contagion.
Émergence
The bats can contaminate humans dides pathologies virales
rectly. There is a very high spatio-tem(IRD et université de la
poral correlation between the Ebola
Méditerranée)
epidemic of May to November 2007
in DRC and the fruit bats’ annual miAddress :
gration, although there is no formal
Centre international de
proof of transmission of the virus from
recherches médicales de
the chiropterans to humans. Villagers’
Franceville (CIRMF)
reports indicate that the bat migraBP 769, Franceville
tion was particularly massive in spring
Gabon
2007. Every April, tens of thousands
of them arrive in the area and break
Tel : +241 07 85 06 13
their journey, settling temporarily on
[email protected]
the islands in the River Lulua, close
to the Kampungu villages. And two
of the three species of migrating bats
REFERENCES :
observed around the agglomeration
Leroy É., Epelboin A., Mon(Hypsignathus monstrosus, Epomops
donge V., Pourrut X., Gonzafranqueti) are among the species suslez J.-P., Muyembe-Tamfum
pected of being the natural reservoir of
J.-J., Formenty P. Human
Ebola virus*.
Ebola Outbreak Resulting
Other potential vectors of Ebola appear
from Direct Exposure to
not to be implicated in this epidemic,
Fruit Bats in Luebo, Dewhich strengthens the idea that these
mocratic Republic of the
chiropterans were involved. Firstly,
Congo, 2007, Vector-borne
villagers did not observe any unusual
and zoonotic diseases, 00
morbidity or mortality in domestic or
(00), 2009
wild animals. Secondly, chimpanzees
and gorillas, which can also be victims
Doi: 10.1089/vbz.2008.0167 of the virus, do not inhabit this region of
the DRC.
Contrary to what was still thought
KEY WORDS :
fairly recently, humans could thereEbola, bats, epidemic, virus
fore contract Ebola haemorrhagic
fever directly from the animal reservoir of the virus : bats. The researFor futher information
The migrant bats (here Hypsignathus monstrosus) break their
journey beside the River Lulua, close by villages of the Kampugu agglomeration in DRC.
Gaëlle Courcoux, coordinator
Délégation à l’information et à la communication
Tél. : +33 (0)4 91 99 94 90 - fax : +33 (0)4 91 99 92 28 - [email protected]