Ebola has wiped out a third of the world's chimpanzee and gorilla populations and could threaten the survival of these already endangered great apes, conservationists have warned.

The current Ebola epidemic in west Africa is the worst known among humans, killing 8641 people, according to the World Health Organisation.

But outbreaks have taken place sporadically in central Africa since the first known case in 1976 and the virus is considered a major threat to gorillas and chimpanzees. In an article for the Jane Goodall Institute, Ria Ghai, an ecologist, wrote that a third of the world's chimpanzees and gorillas have died from Ebola since the 1990s.

"Unlike human epidemics, wild ape epidemics tend to go unnoticed for months or even years," she wrote.


Some of the previous Ebola outbreaks among humans are believed to have stemmed from infected gorillas and chimpanzees, found dead in the forest and butchered for food. Conservationists have called for greater resources to develop a vaccine to help save the animals from extinction. But there are concerns that it could be seen as competing with human research. According to the conservation group WWF, the Ebola mortality rate is estimated at 95 per cent in gorillas and 77 per cent in chimpanzees.

Long-awaited studies of two possible Ebola vaccines are set to begin in West Africa in a couple of weeks, starting in Liberia, US officials said.

The first study will compare the two experimental vaccines with dummy shots in hopes of proving whether either really protects against the Ebola virus, which has devastated Liberia, Guinea and Sierra Leone over the past year.

A second study of one of the vaccines is being planned for Sierra Leone.

New infections are falling, which can make it harder to tell if a vaccine is effective. But clusters of cases continue and Dr Anthony Fauci of the National Institutes of Health said the vaccines could still be useful if there's a rebound, as well as for what he called inevitable future outbreaks of Ebola.

"Unless you extinguish the very last case, it's not over 'til it's over," said Fauci, director of the National Institute of Allergy and Infectious Diseases.

Fauci said up to 27,000 people could ultimately be enrolled in the larger Liberian study, starting with about 600 in the first phase. The study could last as long as a year. The second study could enrol about 6000 people.

- Telegraph Group Ltd, AP