Ebola Epidemics Decimate Central African Apes

PARIS, France, January 19, 2004 (ENS) - The Ebola virus, which kills 80 percent of its human victims within days, has also been wiping out populations of gorillas, chimpanzees and duikers, according to a new study of the Central African disease by an international scientific team. Researchers say that for the first time they have found that animals can also be victims of Ebola epidemics.

The animal Ebola epidemics lead to human epidemics, scientists have found. Ebola hemorrhagic fever in humans appears to result from two successive waves of contamination between species.

The animals contract the virus from the as yet unidentified reservoir, and they die. Then humans who handle their carcasses become infected, spreading the virus in the human population.

Gorillas in Central Africa are at risk of the Ebola virus. (Photo by Dennis DeMello courtesy Wildlife Conservation Society)

The Ebola virus, identified for the first time in 1976 in the Democratic Republic of Congo, formerly Zaire, has caused several deadly epidemics in Central Africa, occurring simultaneously in the Republic of Congo and Gabon.

These outbreaks result from multiple simultaneous transmission events that have triggered the "drastic decline in great ape populations which has been observed in these areas of Africa," the scientists say.

Data obtained during human epidemics that occurred between 1976 and 2001 shows that each of these epidemics developed from a single animal source, then spread from person to person.

However, in the study undertaken between 2001 and 2003, epidemiological findings suggest, on the contrary, that several different and concomitant epidemic chains exist, each stemming from a different single animal source.

Gene sequencing analyses of the virus performed on patients' blood samples confirmed these observations, and also showed that these chains do not result from a common transmitted viral strain but from several strains.

Outbreaks among the great apes seem to hit mainly at times of seasonal changes.

But the exact environmental conditions that foster their emergence are not known. Neither is the host, the natural reservoir of the virus, which contaminates the animals. Research is under way to identify the factors involved.

Beginning in late 2002 and continuing into 2003, the Ebola virus hit humans and wildlife in the northwest section in the Republic of Congo. As of mid-March 2003, at least 100 people had died in the villages of Kelle and Mbomo, according to the Wildlife Conservation Society (WCS), a research organization based at the Bronx Zoo in New York.

Scientist wears protective gloves to examine a gorilla carcass in the Republic of Congo, 2000. (Photo courtesy WCS)

In response to this outbreak, an emergency workshop was held in Brazzaville, Republic of Congo, March 4 to 6, 2003. It brought together government authorities, conservation and human medicine nongovernmental organizations, and virology experts who tried to come up with immediate and long-term action plans to address the Ebola virus.

The workshop was sanctioned by the Congolese Ministry of Health and the Ministry of Forests, with additional participants from the Ministry of Agriculture. Experts and representatives from the Democratic Republic of Congo, and Gabon also participated to provide insights from the previous outbreaks in those countries.

Representatives from the U.S. Centers for Disease Control and Prevention, the World Health Organization, Doctors Without Borders, WWF, and the Wildlife Conservation Society also participated. The workshop was organized by ECOFAC, a regional conservation program supported by the European Community, under the auspices of the Congolese government.

These organizations and agencies contributed data to the IRD study published in "Science" this week.

In an attempt to stem Ebola epidemics, health workers and scientists are teaching forest peoples not to consume the flesh of apes, including those found weakened, sick or dead in forest. But the challenge for conservation of the world's endangered great apes has intensified with the discovery that apes are susceptible to Ebola epidemics.

Conservationists can fight against hunting and habitat destruction; they can create national parks and sanctuaries, but fighting a virus with no understanding of where it originates is much more difficult.

Gorillas and chimpanzees could be pushed to the brink of extinction during the next decade without immediate protective measures, scientists warn.

"If chimpanzees and gorillas are in trouble in Gabon, an area known for its pristine, unbroken forests, than we have a species wide crisis on our hands when it comes to saving these animals," said WCS conservationist Dr. Lee White, who has worked in Gabon for the past 10 years.

Confirmed cases of Ebola hemorrhagic fever have been reported in the Democratic Republic of the Congo, Gabon, Sudan, the Ivory Coast, Uganda, and the Republic of the Congo.