Most-Endangered Wolves May Be Saved By Vaccine
John Pickrell
for National Geographic News
September 27, 2002
The Ethiopian wolf (Canis simensis) is the most endangered species in the
group of animals known as canids. The biggest threat comes from rabies and
other diseases carried by dogs in the wolves’ mountainous habitat, but
researchers now think it may be possible to develop a vaccine that could
dramatically help the species’ survival.
Based on a complex computer model, the scientists say it might be
possible to prevent the wolf’s extinction by vaccinating only 20 percent
to 40 percent of the known populations.
The elegant and long-legged animal with reddish-orange fur lives in the
alpine regions of Ethiopia, 10,000 feet (3,000 meters) or so above sea
level. It is also known as the Simien jackal or the Abyssinian wolf.
The Ethiopian wolf has become so rare that any rescue plan must be
implemented soon, researchers argue.
Claudio Sillero-Zubiri, a zoologist at the University of Oxford in
England, said only seven populations of the wolf remain, totalling less
than 500 adults. That figure “makes the species rarer than gorillas,
pandas, tigers, cheetahs, rhinos, and most other large mammals,” he noted.
Dwindling Numbers
The Ethiopian wolf has declined slowly in population since the end of the
last ice age, when the world warmed and cooler alpine habitats receded
across much of Africa.
Today, habitat destruction and hybridization with domestic dogs have
helped push the species toward extinction.
“The Ethiopian wolf is teetering on the brink,” said James Malcolm, a
biologist at the University of Redlands in California. “The species has
persisted in pockets of habitat which…are now being encroached by people
eking out a living,” he added. In some areas, the wolves are killed by
Ethiopian farmers who blame them for killing sheep and goats. Many of the
animals were also killed indiscriminately during periods of civil war in
the past two decades.
The most serious threat, however, comes from diseases such as rabies, or
canine distemper, carried by dogs from human settlements.
After a rabies outbreak in 1990, the largest known population of
Ethiopian wolves—found in the region’s Bale Mountains—decreased by
two-thirds within two weeks—from about 440 animals to less than 160.
“Fresh carcasses began to appear everywhere,” said Dada Gotelli, a
conservation geneticist at the Institute of Zoology in London.
“We were left with the lingering fear [that it] could happen again,”
said Gotelli, who believes prompt action should be taken to control
further outbreaks of infectious diseases that could wipe out the
Ethiopian wolf.
Toward a Vaccine
Since 1996, Karen Laurenson, a veterinary biologist at the University of
Edinburgh in Scotland and a colleague of Sillero-Zubiri, has been studying
the possibility of vaccinating dogs against rabies as a way of indirectly
protecting the Ethiopian wolf. Her results suggested that up to 70 percent
of all dogs in the region would have to receive the vaccine to have a
positive effect on the wolf populations.
Now, Sillero-Zubiri, Laurenson, and another co-worker, Daniel Heydon at
the University of Guelph in Ontario, are considering direct vaccination of
the wolves.
In a study reported in the October issue of Conservation Biology, the
researchers used complex computer models to test the likelihood of
extinction among wolves that would be vaccinated—if an effective vaccine
were developed—compared with non-vaccinated wolves.
The results suggested that small populations of Ethiopian wolves,
perhaps as few as 25 to 50, were not likely to become extinct in the
next 50 years if they remained rabies-free.
At current levels of rabies, however, most or all remaining populations of
the wolf are highly susceptible to extinction, the researchers concluded.
Previous research has shown that when some wolves in a population become
infected, up to 90 percent of their pack is likely to also develop the
disease.
Malcolm said the finding that only 20 percent to 40 percent of the
wolves would need to be vaccinated is encouraging.
“The bad news is that we have no way of doing it,” because a vaccine to
prevent rabies in the Ethiopian wolf has not yet been invented, he pointed
out.
Yet Sillero-Zubiri is optimistic, arguing that effective oral vaccines
have been developed for foxes, racoons, and skunks in Europe and America.
Such a vaccine could be administered to the wolves in the wild by
delivering the dosages with bait, he said.
Acknowleding that much careful research lies ahead, he said:
“Vaccinating wolves would seem a good idea, but we need to be satisfied
that there will be no side effects.”
Gotelli agreed that the task of vaccine development is urgent. “The
small isolated nature of the remaining wolf populations, together with the
increase of human density in a country streaked by poverty…is like a time
bomb,” she said. “If science doesn’t try to prevent the explosion, the
Ethiopian wolf will be facing its last days.”