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Can Great Apes Be Saved From Ebola?

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Science  13 Jun 2003:
Vol. 300, Issue 5626, pp. 1645
DOI: 10.1126/science.300.5626.1645

Desperate times have some researchers proposing desperate measures, but others argue that the plans would be a possibly dangerous misuse of resources

Ongoing Ebola outbreaks in central Africa are taking a gruesome toll on both humans and great apes. Conservationists, primatologists, and disease experts agree on that much, but in an increasingly heated debate, they are arguing over whether they can or should do anything to limit the spread of the disease.

The outbreaks, which have so far killed more than 150 people and thousands of apes, are spreading ominously toward Congo's Odzala National Park, which shelters one of the world's largest populations of gorillas and chimpanzees. Some researchers argue that drastic measures should be taken to protect the region's great apes. Proposals include transporting hundreds of apes to safe areas and clearing rivers of debris to divide infected from uninfected populations. Anything that slows the current outbreak would be worthwhile, says ecologist Peter Walsh of Princeton University. “We need to knock this thing down right now and give ourselves time for developing things like vaccines” that could confer longer lasting protection, he argues.

But others say such plans are logistical nightmares that might have little or no effect on the spread of the virus. “We may just be stuck at the scene of an accident and there's nothing we can do but watch,” says Les Real, a disease ecologist at Emory University in Atlanta.

Key to settling the debate, Real says, is understanding more about how the virus spreads. Some think the geographic pattern of outbreaks suggests that apes are catching the disease primarily from other apes. Others argue that an unidentified reservoir is an important source of new infections. If the virus is spreading from one ape to another, then attempts to keep infected and uninfected animals apart might make a difference. But if bats or rodents are carrying the virus over long distances, then such measures would be in vain.

Last fall, as word of the epidemic's scale began to emerge, primatologist Christophe Boesch of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, set off an ongoing e-mail discussion among primatologists and conservation organizations working in the region, urging the community to discuss possible interventions. “I don't know the answer,” he says. “I just thought this should be discussed very seriously by people in the field so we can see what is to be gained. There are tens of thousands of great ape and hundreds of human lives at stake” in this remote region.

Dire straits.

Ebola outbreaks are moving toward Congo's Odzala National Park, home to one of the world's largest gorilla populations.


Walsh, who recently published an analysis in Nature of the effects of Ebola and hunting on ape populations (Science, 11 April, p. 232), argues for immediate action. He believes the sporadic human outbreaks—thought to arise mainly from people butchering infected apes—over the last decade in Gabon and Congo are all part of one large epidemic spreading primarily from ape to ape. If that is the case, he says, erecting barriers between infected and uninfected populations could help protect apes that haven't been exposed. Like an army trying to slow an invader's advance, he says, workers could clear rivers of natural bridges that allow infected gorillas and chimps to cross into unexposed areas. “I would at least like to have people out there trying to see if it would work” on an experimental scale, he says, and he has spoken with several potential donors willing to finance such a project.

But clearing rivers on any large scale “would be a Herculean task,” says Conrad Aveling of the European Union conservation organization ECOFAC in Libreville, Gabon. “On a purely practical and logistical level, it's impossible. … We clear 100 kilometers of river for tourists in Odzala National Park, and that is a never-ending job.” Constructing an effective barrier would mean clearing thousands of kilometers of rivers, Aveling says. Another proposal—transporting animals to uninfected areas—would be an unprecedented undertaking that could end up killing more apes than it saves, he says. Even if donors are willing to support such efforts, “we could perhaps better use those dollars to make sure the gorillas survive after the passage of Ebola.”

And if, as other researchers suspect, the virus spreads through other animals, the work could be in vain. “We know there have been human outbreaks in areas without great apes, so clearly there is something else at play,” says William Karesh of the Wildlife Conservation Society in New York City.

Those on both sides of the debate agree that there is no time to waste in tracking down the answers. This week, Karesh, Eric Leroy of the International Center for Medical Research in Franceville, Gabon, and their colleagues arrived in the Lossi gorilla sanctuary in Congo, site of a recent outbreak. They will spend a month tracking and anesthetizing gorillas to collect blood samples that will reveal how many of the animals have been exposed to Ebola.

In the meantime, there is one surefire way to help protect the besieged populations, Karesh says: fight poaching through increased patrols and education programs. “One of the things we can do right now is reduce the hunting pressure. Let's take what we do know—that people can get this disease from eating infected primates—and use that to do something we know will protect great apes.”

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