Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Ebola virus: from wildlife to dogs

05.04.2005


Ebola virus infection in humans provokes a violent haemorrhagic fever. It usually flares up as intense epidemics. These kill 80 % of the people infected. Seven such outbreaks have hit Gabon and the Republic of Congo since 1994, leading to 445 cases resulting in 361 deaths. Ebola virus thus constitutes a grave public health problem in these countries. No medicine or vaccine is currently available, only prevention and rapid control of epidemics by isolation of disease victims can limit its spreading.



Since 2001, IRD research scientists and their partners (1) have been working to unravel the virus’s biological cycle, in other words the whole range of ways in which the virus circulates in its natural environment, from its natural host (or reservoir) right up to humans. They showed that strong epidemics of Ebola have decimated populations of large primates over the past several years in the border regions between Gabon and the Republic of Congo. Human infection appears to occur only in a secondary way, through contact with carcasses of dead animals (2). However, the virus’s natural cycle is not restricted just to transmission from the reservoir to the non-human primate and then to humans. It is quite possible that several reservoir species co-existent and that many other animal species can become infected, thus contributing to propagation of the virus in nature.

A serological investigation conducted from 1980 to 2000 on 790 nonhuman primates from Cameroon, Gabon and the Republic of Congo, belonging to 20 different species, hence revealed that 12.9 % of wild chimpanzees carry Ebola virus antibodies, several of the positive samples dating from before the first epidemics in these countries. These results therefore indicate that chimpanzees are regularly in contact with the animal virus reservoir and that some of them develop non-fatal infections. The presence of specific antibodies in the animals taken before the epidemics means that the Ebola virus has probably been circulating for a long time in Central African forests. The detection of such antibodies in other primate species (including 5 drills, 1 baboon and 1 mandrill) suggests that circulation of the virus involved many contamination events between distinct animal species. Thus, the multiplicity of infected species, their different susceptibilities to the virus and the great differences in their ways of life, are indicators of the complexity of Ebola virus’s circulation in its natural environment. These observations also show that an epidemic or sporadic cases can appear at any moment in the sub-region of Central Africa as a whole.


Moreover, during the latest epidemics in Gabon and the Republic of Congo, there were many cases where dogs had eaten remains of dead animals infected with the virus, nonetheless without showing visible clinical signs. In order to confirm that these dogs had indeed come into contact with the virus, the scientists looked for the presence of specific Ebola virus antibodies in their blood (3). The percentage of dogs carrying such antibodies increases linearly and significantly the closer they are found to foci of the outbreaks. From 9 % in the two large cities of Gabon, antibody prevalence goes up to 25 % in the untouched villages of the epidemic area, reaching 32 % in the villages where human cases have been attributed to an infected-animal source. These domestic animals could therefore become infected and excrete virus over a given period, thus becoming a potential source of infection for humans. This could explain certain as yet un-elucidated human infections. It now appears necessary to assess the role of dogs in Ebola fever outbreaks and take this risk into account in epidemic-control measures. These animals could furthermore be used as indicators of the presence of the virus in the regions where, besides the appearance of cases of both animal and human deaths, there is no external sign as to whether or not Ebola virus is present.

This research work as a whole indicates the progress that has been made over the past years in the understanding the ways in which the virus circulates in its natural environment. Although the reservoir has not yet been identified, investigations are under way to identify the stages which, starting from this reservoir, lead to the emergence of human epidemics. Knowledge of the reservoir animal and of the virus’s natural cycle should assist in devising suitable prevention strategies against Ebola epidemics.

(1) This research, conducted since 2001, involves a partnership between the IRD, the CIRMF (Centre International de Recherches Médicales de Franceville, Gabon), the Center for Diseases Control and Prevention of Atlanta (USA) and the Centre Pasteur of Cameroon.

(2) See Scientific news sheet n° 192 – Jabuary 2004, " Virus Ebola : les populations de grands singes menacées ". reference publication: E.M. Leroy, P. Rouquet, P. Formenty, S. Souquière, A. Kilbourne, J.M. Froment, M. Bermejo, S. Smit, W. Karesh, R. Swanepoel, S. R. Zaki, and P.E. Rollin– Multiple Ebola Virus Transmission Events and Rapid Decline of Central African Wildlife, Science, vol. 303 n° 5655, 16 January 2004.

(3) The virus which is rife in Gabon, the Republic of Congo and the Democratic Republic of Congo belongs to the most widespread and most virulent of the four known Ebola sub-groups, the Zaire sub-type, which exists in several strains.

Helene Deval | alfa
Further information:
http://www.ird.fr

More articles from Life Sciences:

nachricht Newly designed molecule binds nitrogen
23.02.2018 | Julius-Maximilians-Universität Würzburg

nachricht Atomic Design by Water
23.02.2018 | Max-Planck-Institut für Eisenforschung GmbH

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Attoseconds break into atomic interior

A newly developed laser technology has enabled physicists in the Laboratory for Attosecond Physics (jointly run by LMU Munich and the Max Planck Institute of Quantum Optics) to generate attosecond bursts of high-energy photons of unprecedented intensity. This has made it possible to observe the interaction of multiple photons in a single such pulse with electrons in the inner orbital shell of an atom.

In order to observe the ultrafast electron motion in the inner shells of atoms with short light pulses, the pulses must not only be ultrashort, but very...

Im Focus: Good vibrations feel the force

A group of researchers led by Andrea Cavalleri at the Max Planck Institute for Structure and Dynamics of Matter (MPSD) in Hamburg has demonstrated a new method enabling precise measurements of the interatomic forces that hold crystalline solids together. The paper Probing the Interatomic Potential of Solids by Strong-Field Nonlinear Phononics, published online in Nature, explains how a terahertz-frequency laser pulse can drive very large deformations of the crystal.

By measuring the highly unusual atomic trajectories under extreme electromagnetic transients, the MPSD group could reconstruct how rigid the atomic bonds are...

Im Focus: Developing reliable quantum computers

International research team makes important step on the path to solving certification problems

Quantum computers may one day solve algorithmic problems which even the biggest supercomputers today can’t manage. But how do you test a quantum computer to...

Im Focus: In best circles: First integrated circuit from self-assembled polymer

For the first time, a team of researchers at the Max-Planck Institute (MPI) for Polymer Research in Mainz, Germany, has succeeded in making an integrated circuit (IC) from just a monolayer of a semiconducting polymer via a bottom-up, self-assembly approach.

In the self-assembly process, the semiconducting polymer arranges itself into an ordered monolayer in a transistor. The transistors are binary switches used...

Im Focus: Demonstration of a single molecule piezoelectric effect

Breakthrough provides a new concept of the design of molecular motors, sensors and electricity generators at nanoscale

Researchers from the Institute of Organic Chemistry and Biochemistry of the CAS (IOCB Prague), Institute of Physics of the CAS (IP CAS) and Palacký University...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

2nd International Conference on High Temperature Shape Memory Alloys (HTSMAs)

15.02.2018 | Event News

Aachen DC Grid Summit 2018

13.02.2018 | Event News

How Global Climate Policy Can Learn from the Energy Transition

12.02.2018 | Event News

 
Latest News

Basque researchers turn light upside down

23.02.2018 | Physics and Astronomy

Finnish research group discovers a new immune system regulator

23.02.2018 | Health and Medicine

Attoseconds break into atomic interior

23.02.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>