Vaccination to Protect Apes Against Ebola

Vaccination to Protect Apes Against Ebola



   
April 2007 - Outbreaks of Ebola 
virus over the past 12 years have killed roughly 25 percent of 
the world gorilla population, and now the scientists who 
documented these deaths say vaccination of wild gorillas could 
help protect those that remain. 
A study published in the May issue of the journal "The 
American Naturalist" provides hope that newly developed 
vaccines can control the devastating impact of Ebola on wild 
apes. 
The hopeful clues come from the discovery that outbreaks may 
be amplified by Ebola transmission between ape social groups. 
"It means that vaccinating one gorilla does not protect only 
that gorilla, it also protects gorillas further down the 
transmission chain," said Peter Walsh of the Max Planck 
Institute for Evolutionary Anthropology in Leipzig, Germany, 
the lead author on the study. 
"Thus, protecting remaining ape populations may not require 
vaccinating a high proportion of individuals, as many people 
naively assume," Walsh said. Scientist Peter Walsh measures
 gorilla dung in his research to 
estimate the abundance of gorillas and chimpanzees and monitor 
the effects of the Ebola virus. 
Direct encounters between gorilla or chimpanzee social groups 
are rare. So, when reports of large ape die-offs first 
surfaced in the late 1990s, outbreak amplification was assumed 
to be through spillover from some unknown reservoir host. But 
more recent research by Walsh and his colleagues suggests that 
Ebola transmission between ape groups might occur through 
routes other than direct social encounter. 
Initial spillover from a reservoir host appears to have 
triggered an epidemic that spread from gorilla social group to 
gorilla social group. 
The new study was conducted at three sites in northern 
Republic of Congo by Walsh and other researchers from the Max 
Planck Institute, David Morgan of England's Cambridge 
University, and Diane Doran of New York's Stony Brook 
University. 
They found that as many as four different gorilla groups fed 
in the same fruit tree on a single day. In this way, infective 
body fluids deposited by one group might easily be encountered 
by a subsequent group, the researchers say. 
Chimpanzees and gorillas also fed simultaneously in the same 
fruit tree at least once every seven days. 
The study also provided the first evidence that gorillas from 
one social group closely inspect the carcasses of gorillas 
from other groups. The researchers point out that contact with 
corpses at funerals is a major mechanism of Ebola transmission 
in humans. 
Together with other recent observations on patterns of gorilla 
mortality, these results make a strong case that transmission 
between ape social groups plays a central role in Ebola 
outbreak amplification. A Western lowland gorilla in the Congo Basin.  
Particularly troubling has been the concentration of Ebola 
impact on large, remote protected areas that were designed to 
be central to ape conservation efforts. 
Ebola has not made apes totally extinct from these areas but 
it has pushed once huge populations down to smaller sizes at 
which they are dramatically less resilient to illegal hunting 
and other looming threats. 
The current lack of a vaccination program is not due to a lack 
of vaccine options, as several different vaccines have now 
protected laboratory monkeys from Ebola and major vaccine labs 
are anxious to help. 
"Uncertainty about whether a large Ebola control effort was 
necessary or even possible has paralyzed large donors and 
major conservation organizations," said Walsh in December, 
announcing the results of a separate study that first showed 
that 93 percent (221 of 238) individually known gorillas at 
the Lossi Sanctuary in northwest Congo were killed by Ebola 
during outbreaks in 2002 and 2003. 
The scientists then used transect surveys to show that 95 
percent gorilla mortality rates extended over a much larger 
area of several thousand square kilometers. Chimpanzees were 
also heavily affected, with a mortality rate of 77 percent. 
"We are hoping that the starkness of our results will push 
some public or private donor to finally commit the two or 
three million dollars necessary to develop a safe and 
effective way of delivering Ebola vaccine to wild apes," said 
Walsh. 
Walsh contends that Ebola vaccination is a cost effective 
method of ape conservation. 
"People in the conservation community are intimidated by the 
up-front costs of vaccination and would prefer to instead 
spend the money on anti-poaching. What they are not factoring 
in is the fact that one year of Ebola vaccination could save 
as many apes as decades of anti-poaching," Walsh said. "We 
need to do both." 
Walsh also points out that Ebola has the potential to quickly 
destroy years of ecotourism investment. For example, a gorilla 
habituation program at Lossi was set up in the mid-1990s in 
collaboration with the European Union's Ecosystem Forestiere 
d'Afrique Centrale project to bring ecotourism revenue to 
local people. 
Ebola not only wiped out the habituated gorillas at Lossi, it 
neutralized years of ecotourism investment in neighboring 
Odzala National Park by devastating gorilla populations there.
 "We are in a period where relatively modest investments in 
both Ebola control and anti-poaching would go a very long way 
towards insuring the future of our closest relatives," said 
Walsh. "Let's not blow it." 
Walsh and his colleagues now are searching for funding to 
implement a vaccination program using one of the several 
vaccines that have successfully protected laboratory monkeys 
from Ebola. 

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