During every recent human outbreak of the Ebola virus—which oftencauses victims to bleed to death—gorilla carcasses have turned up innearby forests, but scientists were uncertain about the extent of thedisease’s impact. New data confirm that these gorilla deaths are notisolated incidents but are part of a devastating wave of Ebolainfections afflicting nonhuman primates.
Ebola has killed as many as 5,500 gorillas in Gabon and theDemocratic Republic of the Congo since 2002, according to University ofBarcelona primatologist Magdalena Bermejo. She and her colleaguesdocumented the loss of hundreds of gorillas at their study sites.Overall, more than 90 percent of the animals surveyed died. Genetictesting of the carcasses confirmed Ebola as the culprit. Based on thesize of the affected area, a quarter of the world’s gorillas may havebeen killed by the disease in the past decade. Gorillas aren’t the onlyvictims; Bermejo estimates that the virus may have wiped out more than80 percent of the local chimpanzees too.
Some scientists had suspected that apes mostly caught Ebola from avirus-carrying reservoir species, like bats or insects. The observeddisease pattern strongly suggests the virus is also passing from ape toape through direct contact, just as it has been shown to do in humans.
Strange as it sounds, this may be good news, says Peter Walsh,ecologist at the Max Planck Institute. Ape-to-ape transmission meansthat vaccinating groups could break the chain of infection. Multiplevaccines have already been shown to protect lab monkeys, Walsh says,adding that there is no time to lose in preparing a vaccination programfor gorillas. Ebola alone may not drive the threatened giants toextinction, he says, “but it may push them onto a slippery slope thatwill be very difficult to climb back up, because other factors arepushing too.”