Ebola outbreaks kill 25% of world's gorillas

12 January 2007 General News

The Ebola virus, a nasty  hemorrhagic fever that causes massive organ failure  

and bleeding, is killing  thousands of endangered gorillas across Central

African forests according to new  research published in the journal Science.  

While the findings suggests that even  in strictly protected wildlife sanctuaries  

gorillas are not safe, the research  provides insight on how to control Ebola  

outbreaks among wild gorillas (Gorilla  gorilla) and chimpanzees (Pan  



The new study, led by  Magdalena Bermejo of the University of Barcelona ,  

provides strong evidence that  Ebola killed at least 5,500 at a single site -- the  

western portion of the Lossi  Sanctuary in northwest Republic of Congo -- in  

outbreaks between 2001 and 2005.  Bermejo , along with José Domingo Rodríguez  

Teijeiro ( University of Barcelona ),  Carles Vilà ( Uppsala University in

), and Peter Walsh (Max Planck  Institute for Evolutionary Anthropology) found  

extraordinarily high rates of ape  mortality caused by Ebola outbreaks in 2002

and 2003 in Lossi. Gorillas suffered  a 95 percent mortality rate, while  

chimps had 77 percent mortality rate,  according to transect surveys conducted by

the researchers. While exact numbers  aren't yet known, the team estimates

that Ebola outbreaks over the past twelve  years may have killed 25 percent of  

the world's gorilla population.  


"We  don't have a scientifically rigorous estimate of how many gorillas there  

are in  the world, much less how many have been killed by Ebola," said Dr.  

Peter Walsh,  a Group Leader in the Department of Primatology of the Max Planck  

Institute for  Evolutionary Anthropology in Leipzig . "But based on the

proportion of  prime gorilla habitat that has been affected and typical Ebola  

mortality rates,  an educated guess is that about 25% of the world gorilla

population has been  killed by Ebola in the last 12-15 years."  

The researchers say the Ebola  outbreaks are particularly troubling because

they are occurring in areas set  aside for ape conservation.


"The conservation implications are huge  because the outbreaks have been

concentrated in large, remote protected areas  that were supposed to be the

stronghold for gorilla and chimpanzee protection,"  Walsh told via

email. "Ebola is not going to drive gorillas  extinct, but it is going to push  

them onto a slippery slope which it will be  difficult to climb back up."  


The researchers say that while Ebola has  not totally extirpated apes from 

Lossi, it has reduced once large populations  down to smaller sizes at which

they are "significantly less resilient to illegal  hunting and other looming



"Although habitat loss is a huge  problem for gorillas and chimpanzees in

eastern Africa and chimpanzee  populations in west Africa, it is a very distant

third to Ebola and bushmeat  hunting in western equatorial Africa where these

Ebola outbreaks have been  occurring," Walsh told "Confinement to

small populations has not  played a role in these outbreaks. To the contrary,

these outbreaks have been in  really large, high density populations. Thus,

the story is really that it is  Ebola which is reducing western gorillas to

small populations (not habitat  loss), at which time they then become more

susceptible to factors such as  hunting."


There is also concern that Ebola appears to be spreading  towards other

protected areas in the region, but team notes that a vaccination  campaign could

reduce the impact of Ebola in these yet affected gorilla  populations. Since the

disease appears to be spread from gorilla social group to  gorilla social

group, and not from a reservoir host, targeted vaccination could  break the chain

of transmission. Further, because the research suggests that  Ebola is

progressing at a consistent state, a vaccination campaign could be  "targeted just

ahead of the advancing wave."


"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," write the researchers

in a news release.  "Rather," said Walsh, "Uncertainty about whether a large

Ebola control effort  was necessary or even possible has paralyzed large donors

and major conservation  organizations. 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."  


"The really depressing part is that, from a technical  standpoint,

vaccination is very doable," lamented Walsh. "The remaining  technical hurdles are not

trivial, but they are much lower than those already  jumped. What is holding us

back is not technical capacity but rather a failure  of imagination and of



Walsh says that the initial costs of a  vaccination campaign scare off

conservation groups.


"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. We need to do both."


"In the big  picture, the costs involved in mounting an Ebola control program

for apes are  trivial: perhaps $2-3 million to do lab tests on safety and

efficacy and field  studies on vaccine delivery, with the costs of full

implementation depending on  what delivery method (dart or bait) was used and how many animals were  vaccinated," he added. "To put things in perspective, the

government is  spending $35 million on a retirement home for 200 laboratory

chimpanzees. $35  million would not only vaccinate many thousands of wild apes it

would also pay  for decades of anti-poaching."


Walsh further notes that Ebola has set  back ecotourism development -- an

important potential source of revenue for  Republic of Congo -- by frightening

away investors and ecotourists as well as  killing gorillas in Odzala National Park and Lossi.


"The real tragedy is  that a relatively small amount of money, a few million

dollars, could make a  huge difference," Walsh said. "If we don't spend it

now, we will have to spend  ten times as much to intensively manage the small

remnant populations in the  future. Why do we always wait until it is too late?"

"When people look  back 100 years from now, most won't even remember .

One thing they will  remember is that we sat by and did nothing while our

closest relatives slipped  away. This is a case where one wealthy individual could

have an enormous impact.  He or she could quite literally save gorillas from

ecological  extinction."



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