Published Date: 2009-05-30 20:00:06
Subject: PRO/AH/EDR> Ebola hemorrhagic fever, fruit bat - Congo DR, 2007
Archive Number: 20090530.2014

EBOLA HEMORRHAGIC FEVER, FRUIT BAT - DEMOCRATIC REPUBLIC OF CONGO, 2007
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Date: Fri 29 May 2009
Source: allAfrica.com, ex SciDev.Net [edited]
<http://allafrica.com/stories/200905290730.html>


Central Africa: scientists find more signs of bats' role in Ebola
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Ebolavirus, a filovirus, causes fever, vomiting, diarrhoea, and sometimes
bleeding. There is no treatment or vaccine and 25-90 per cent of infected
people die. The virus is transmitted by direct contact with infected blood,
body fluids, and tissues. The new findings have emerged from data collected
in the remote Kasai-Occidental and Kasai provinces of the Democratic
Republic of Congo (DRC) which experienced a large Ebola [hemorrhagic fever]
outbreak in 2007 in which 186 people died. Some members of the research
team helped discover in 2005 that fruit bats are a natural reservoir of the
ebolavirus.

For the new study, researchers led by Eric Leroy from the International
Centre for Medical Research in Franceville, Gabon, interviewed locals about
the background of the ebolavirus infection cases. They were told that the
annual migration of the fruit bat _Hypsignathus monstrosus_ was
particularly large in 2007. Bats are an important source of protein in the
area as wild animals are in short supply. They are often shot and then sold
covered in blood.

The researchers believe the source of the 2007 outbreak was a man who
bought bats at market. He survived, experiencing only a low fever, but his
4 year old daughter died after developing a sudden fever accompanied by
vomiting. A family friend who prepared the girl's body for burial was
subsequently infected and went on to infect 11 members of her family, all
of whom died. Researchers say their study suggests infection is only
transmitted after prolonged contact with an infected person, meaning it may
be easier to contain an outbreak than was previously believed.

Jean-Jacques Muyembe, epidemiologist at the DRC's National Biomedical
Research Instituteand co-author of the study, told SciDev.Net that the team
will continue to retrace events around outbreaks and carry out ecological
studies on bats "to definitely prove that these bats are the direct vectors
of Ebola [hemorrhagic fever] to humans." Vital Mondonge, a co-author from
the infectious disease section of DRC's health ministry, says that the bat
migration should be a focus of efforts to prevent ebolavirus infection.
Chimpanzees and gorillas are also known ebolavirus vectors. Bats, however,
appear not to die from ebolavirus [infection], suggesting they play a role
in maintaining the virus in tropical forests. The research was published in
March in Vector-borne and Zoonotic diseases: Vector-Borne and Zoonotic
Diseases doi 10.1089=vbz.2008.0167 (2009).

[byline: Esther Tola and Christina Scott]

--
Communicated by:
ProMED-mail rapporteur Susan Baekeland

[This report is based on the following publication: EM Leroy, A Epelboin, V
Mondonge, X Pourrut, J-P Gonzalez, J-J Muyembe-Tamfum, et al. Human Ebola
outbreak resulting from direct exposure to fruit bats in Luebo, Democratic
Republic of Congo, 2007. Vector-borne and Zoonotic Diseases, 28 Mar 2009
<http://www.liebertonline.com/doi/abs/10.1089/vbz.2008.0167>.

Abstract: "Twelve years after the Kikwit Ebola outbreak in 1995, ebolavirus
reemerged in the Occidental Kasai province of the Democratic Republic of
Congo (DRC) between May and November 2007, affecting more than 260 humans
and causing 186 deaths. During this latter outbreak we conducted several
epidemiological investigations to identify the underlying ecological
conditions and animal sources. Qualitative social and environmental data
were collected through interviews with villagers and by direct observation.
The local populations reported no unusual morbidity or mortality among wild
or domestic animals, but they described a massive annual fruit bat
migration toward the southeast, up the Lulua River. Migrating bats settled
in the outbreak area for several weeks, between April and May, nestling in
the numerous fruit trees in Ndongo and Koumelele islands as well as in palm
trees of a largely abandoned plantation. They were massively hunted by
villagers, for whom they represented a major source of protein. By tracing
back the initial human-human transmission events, we were able to show
that, in May, the putative 1st human victim bought freshly killed bats from
hunters to eat. We were able to reconstruct the likely initial human-human
transmission events that preceded the outbreak. This study provides the
most likely sequence of events linking a human Ebola [hemorrhagic fever]
outbreak to exposure to fruit bats, a putative virus reservoir. These
findings support the suspected role of bats in the natural cycle of
ebolavirus and indicate that the massive seasonal fruit bat migrations
should be taken into account in operational Ebola [hemorrhagic fever] risk
maps and seasonal alerts in the DRC."

In their discussion the authors point out that these findings strongly
suggest that ebolavirus can be contracted by humans through direct exposure
to fruit bats, and the massive fruit bat migrations should therefore be
taken into account in operational Ebola [hemorrhagic fver] risk maps and
seasonal alerts. Specific studies of the routes and dates of fruit bat
migration are needed. However, in the short term, it may be difficult or
even impossible to halt human consumption of fruit bats, which represent a
readily available and abundant source of protein, especially as many game
species are protected or becoming rare.

The authors point out in addition that these observations raise several
questions. Firstly, why was there only one bat-to-human transmission event?
The outbreak only really started after the 3rd human case had occurred.
Transmission from the father to his daughter, then from the girl's corpse
to another person, took place in very particular circumstances and went
unnoticed. In fact, it is highly likely that several other persons were
infected by bats but the circumstances required for subsequent
human-to-human transmission were not present.

Secondly, why was only one secondary case observed among all the people who
came into contact with patient? The mild illness (isolated fever) in the
primary case suggests a low viral load. This would imply a low risk of
transmission to another person, except in certain conditions (such as,
close and long-lasting contact, with a young child, for example).

Thirdly, why was the first secondary case so rapidly fatal (4 days)? The
answer is probably that this patient, being a young child, succumbed
rapidly to untreated dehydration due to vomiting and diarrhoea.

The full text of the paper contains a map of the location of the outbreak
and an image of the fruit bat _Hypsignathus monstrosus_ identified as the
carrier of the virus:
<http://www.liebertonline.com/doi/abs/10.1089/vbz.2008.0167>. - Mod.CP]

See Also

2007
---
Ebola hemorrhagic fever - Congo DR (13) 20071121.3758
Ebola hemorrhagic fever - Congo DR (11): WHO 20071003.3270
Ebola hemorrhagic fever - Congo DR (10) 20071001.3245
Ebola hemorrhagic fever - Congo DR (09) 20071001.3245
Ebola hemorrhagic fever - Congo DR (08) 20070926.3191
Ebola hemorrhagic fever - Congo DR (07) 20070923.3156
Ebola hemorrhagic fever - Congo DR (06) 20070921.3138
Ebola hemorrhagic fever - Congo DR (05): WHO 20070920.3132
Ebola hemorrhagic fever - Congo DR (04) 20070916.3076
Ebola hemorrhagic fever - Congo DR (03): WHO 20070914.3049
Ebola hemorrhagic fever - Congo DR (02) 20070912.3026
Ebola hemorrhagic fever - Congo DR 20070910.2996
Undiagnosed illness - Congo DR (Kasai Occidental): WHO, RFI 20070901.2882
Viral hemorrhagic fever - Congo DR (Kasai Occidental): susp. 20070829.2837

....................cp/ejp/sh


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