After a rabies outbreak in 1990, the largest known population of Ethiopian wolves—found in the region's Bale Mountains National Park—decreased by two-thirds within two weeks—from about 440 animals to less than 160.
"Fresh carcasses began to appear everywhere," said Dada Gottelli, a conservation geneticist at the Institute of Zoology in London.
"We were left with the lingering fear [that it] could happen again," said Gottelli, 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 conservation biologist and veterinarian 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.
Acknowledging 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."
Gottelli 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."
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