Ebola hit the headlines in 2014 with an unprecedented outbreak in West Africa that has claimed nearly 9,000 lives across the three hardest-hit countries. But humans aren’t the only one affected by Ebola — the deadly disease has also wiped out a staggering one-third of gorilla and chimpanzee populations since the 1990s.
Currently, scientists say the Ebola virus is the single greatest threat to the survival of both species.
Statistics show that the virus is even more deadly to great apes than it is for humans, with mortality rates as high as 95 percent for gorillas and 77 percent for chimpanzees. Humans have around a 40 percent chance of survival with appropriate treatment, although the case fatality rate in the 2014 outbreak is estimated at 70 percent.
Meera Inglis, a PhD student in conservation policy at the University of Sheffield in the UK, highlights the grave situation this week on The Conversation, stating that Ebola is at the heart of several catastrophic declines in great ape populations.
The outbreaks are infrequent, but when they strike they can wipe out huge swathes of the animals, especially if the carcasses are left uncollected.
In 1995, an outbreak killed off 90 percent of gorillas in a national park in Gabon. In 2002-2003 another outbreak killed 5,000 gorillas in the Democratic Republic of Congo. With an estimated 100,000 gorillas left in the wild, that’s a major blow, says Inglis.
She points out that Africa’s great apes are also under attack from poaching, habitat destruction, war and other infectious diseases. The lack of habitat means that infected animals are more likely to come into contact with each other, and therefore more likely to contract the virus; it’s a vicious cycle, Inglis says.
The result of these growing challenges is that both eastern gorillas and western gorillas have been listed as endangered since 2008, with dwindling numbers of the animals making the threat of Ebola even greater.
The spread of the deadly virus could be curbed by vaccinating the animals — a safe and effective vaccine for gorillas and apes has already been developed, unlike for humans. However, trials of the vaccines haven’t yet involved testing vaccinated chimps with the live virus.
“Across much of Europe, medical research on great apes is either banned or highly restricted because of their cognitive similarity to humans. The question is whether or not we should make an exception in this case,” says Inglis .
Vaccinating the great apes could also help humans, since contact with infected animals has been found to cause secondary epidemics in humans. Efforts to restore the animals’ forest habitat could also help curb the spread of the virus, Inglis says, “as larger forested areas would reduce the chances of infected animals coming into contact with one another.”
The connection between the health of wildlife and that of humans is well documented. In the book Spillover, science writer David Quammen noted that wildlife deaths in surrounding forests are harbingers of outbreaks in human villages. Additionally, there is a long history of diseases spreading from great apes to humans, and perhaps from humans to great apes:
- HIV, the virus that causes AIDS, originated from chimps and other primates.
- Gorillas may have given humans pubic lice, or “the crabs.”
- There have been suspicions that chimps at Gombe Stream National Park in Tanzania contracted polio from humans.
- There have also been concerns that gorillas contracted yaws, a disease related to syphilis that is not sexually transmitted, from humans.
- Gorillas and chimpanzees in West Africa have been killed by outbreaks of anthrax. This may have originated from cattle herded by humans, although scientists say these may have been natural events that just exist there in the forests.