Ebola Killing Thousands of Gorillas, Study Says

Kate Ravilious
for National Geographic News
December 7, 2006
The Ebola virus is marching steadily across western and central Africa,
wiping out more than 90 percent of the gorillas in its path and
threatening the species with extinction, a new study says.

About 5,000 gorillas were killed by the virus in one study area alone, according to results to be published in tomorrow's issue of the journal Science.

Ebola causes a hemorrhagic fever, resulting in massive internal and external bleeding that kills within two weeks of symptoms appearing. There is no known cure, and in humans the mortality rate is around 80 percent.

The virus is named after the Ebola River in the Democratic Republic of the Congo, near where the first known outbreak occurred in 1976.

Ebola is moving at a rate of around 31 miles (50 kilometers) per year in western and central Africa, experts say. Most of the area's remaining gorillas live within about 124 miles (200 kilometers) of the current outbreak.

"[Ebola] has already swept through two of the largest gorilla reserves and three or four of the smaller ones," said study team member Peter Walsh of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany.

"The outlook is pretty bleak."

Not Just Humans

Scientists have long known that apes were susceptible to Ebola. But until now they had no easy way to judge how serious the problem was.

But the new research, led by Magdalena Bermejo from the University of Barcelona in Spain, clearly lays out the devastating effects of Ebola on gorillas.

Bermejo's team has been monitoring gorilla populations in the Lossi Sanctuary in the northwest of the Republic of the Congo since 1995.

In October 2002 they began to find gorilla carcasses inside the sanctuary. Tests revealed that the gorillas had died from the Ebola virus.

Within a four-month period 130 of the 143 gorillas the researchers were following had died.

Since then the scientists have followed gorilla populations throughout 1,500 square miles (4,000 square kilometers) of the surrounding area.

Bermejo and colleagues estimate that more than 5,000 gorillas died in the area from the disease, with each Ebola outbreak resulting in greater than 90 percent mortality.

"A quarter of the gorillas in the world have died from Ebola in the last 12 years," Walsh told the Reuters news service. "It's huge."

Vaccine Hope

It is not yet clear how the virus remains hidden between outbreaks or spreads, Walsh said. But there are some indications that fruit bats may be the culprits. (Related: "Fruit Bats Likely Hosts of Deadly Ebola Virus" [November 30, 2005].)

"Add commercial hunting to the mix, and we have a recipe for rapid ecological extinction," the authors write in Science. "Ape species that were abundant and widely distributed a decade ago are rapidly being reduced to tiny remnant populations."

There is a glimmer of hope, however, Walsh added—a newly developed vaccine that has been shown to be effective at protecting laboratory monkeys from the Ebola virus.

"If we can develop this vaccine for gorillas, then I think it is feasible to carry out a vaccination program," Walsh said.

He estimates that it would cost around two million U.S. dollars to develop the vaccine and around five million dollars to vaccinate a sufficient number of gorillas.

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