Is Ebola Driving Gorilla Extinction?

A year into West Africa's Ebola epidemic, the WHO has reported more than 7,500 deaths and nearly 20,000 confirmed cases among humans. And while it's understandable why the media has focused on these tragic numbers, some researchers are saying that we're missing something equally tragic: nearly a third of the world's gorillas and chimpanzees have died from Ebola since the 1990s.

Ebola isn't exactly a virus that needs an introduction*. It has been causing complete disarray in West Africa for the greater part of the last 12 months, jumping from Guinea's most remote regions to its capital, and on to Liberia, Sierra Leone, and other bordering countries. Symptoms include severe fever, vomiting, diarrhea, and horrific bleeding from the eyes, ears, mouth, and rectum.

And while that sounds bad enough for human cases, it's so much worse for great apes (gorillas, chimps, etc.) that boast a mortality rate ranging from 77 to 95 percent. Among humans, the virus is known to kill only half its victims, and that statistic is expected to improve as healthcare facilities become more practiced in responding to and treating an infection, according to the World Health Organization (WHO).

Meera Inglis, a conservation policy expert at the University of Sheffield, recently made the case in The Conversation that the rush for finding and distributing an effective Ebola vaccine should also be aimed at helping great apes too.

After all, the IUCN has listed the Eastern Gorilla (Gorilla beringei) as endangered and the Western Gorilla (Gorilla gorilla) as critically endangered. Both of these populations have heavily suffered from Ebola outbreaks in the recent past.

Inglis reported how in 1995, an outbreak killed more than 90 percent of the gorillas in Minkébé Park in northern Gabon. Also, in 2002 and 2003, a year-long outbreak of ZEBOV (the Zaire strain of Ebola) in the Democratic Republic of Congo killed an estimated 5,000 Western gorillas.

"It's hard to accurately count such elusive creatures but the WWF estimates there are up to 100,000 left in the wild - so a single Ebola outbreak wiped out a considerable chunk of the world's gorilla population," she explained.

Inglis is not alone in her concern, either. Sadi Ryan, from the SUNY College for of Environmental Science and Forestry, Syracuse, and Peter D. Walsh from the University of Cambridge published a study back in 2011 that details how a single Ebola outbreak - one just a fraction of the size of the epidemic that West Africa is experiencing - could set ape populations back so far that it would take several lifetimes for them to recover. This would only be exacerbated by other threats to gorillas and chimps more commonly heard about, such as poaching, deforestation, and pollution. (Scroll to read on...)

A study published last year in the Journal of Animal Ecology adds a bit of context to these concerns, finding evidence that Ebola disrupts gorillas in a very unique way.

Investigators detailed how, once gorillas become aware of an Ebola threat, they begin to purposely isolate themselves, no longer interacting with neighboring populations and only rarely breeding. The result? The virus quickly runs out of hosts, disappearing from shrinking populations entirely in the course of a few months.

However, this also leads to reduced birth rates and disrupted social dynamics among normally very communal animals. Researchers worry that it could take generations for gorilla groups to move back and repopulate a region.

"At this moment in time Ebola is the single greatest threat to the survival of gorillas and chimpanzees," Inglis argues. "If we do not act fast, these may prove to be the last decades in which apes can continue to live in their natural habitat."

So what can be done?

"As a short-term strategy, vaccination could prove enormously useful in tackling the Ebola crisis in apes," Inglis wrote.

Vaccines are often tested on primates first before being prepared for human trials. Adding a stage that also specializes a vaccine for apes, she argues, shouldn't be too hard. However, many nations have banned medical experimentation on great apes specifically because of how cognitively similar they are to humans - an ethical argument of personhood.

"The question," Inglis presses, "is whether or not we should make an exception in this case."

*Explore the history of Ebola here.

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