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"World's Rarest Dog" Could Be Saved With Rabies Vaccine

Sean Markey
for National Geographic News
October 12, 2006
 
Close monitoring and rapid, targeted vaccinations may be the best way to protect the Ethiopian wolf, the world's rarest canine, against extinction.

In today's issue of the journal Nature, U.K. scientists suggest that immunizing just 30 percent of the wolf population at the first sign of an outbreak is sufficient to safeguard the endangered species from major outbreaks of rabies and other deadly diseases.

Only about 500 Ethiopian wolves remain in the wild, and the species has been ravaged by rabies epidemics at least twice in the recent past. But completely immunizing all of those animals is too time-consuming, given current technology.

The new study shows that even limited immunizations of wild canine species such as the Ethiopian wolf against rabies is "safe and effective," said lead author Dan Haydon, an ecologist and epidemiologist at the University of Glasgow in Scotland.

(Related: "Most-Endangered Wolves May Be Saved By Vaccine" [September 27, 2002].)

"[That is] something that's not always been agreed upon in the conservation community," Haydon added.

Rarest Dog

Listed as critically endangered by the World Conservation Union, Ethiopian wolves roam the isolated mountain enclaves of the Ethiopian highlands (Ethiopia map).

The rust-colored canine, closely related to the gray wolf, lives in small, social packs that meet three times a day and occupy territories that span just a few miles. (Get wolf pictures, profiles, and more.)

Unlike other wolves, the species hunts alone, with individuals leaving their groups in the late morning and early afternoon in search of giant mole rats and grass rats.

Although it is protected, the wolf faces two major threats to its long-term survival: fatal disease epidemics introduced by domestic dogs and habitat degraded by livestock grazing.

In Bale Mountain National Park, home to some 350 wolves, for example, large rabies outbreaks in 1993 and 2003 wiped out 75 and 76 percent respectively of the wolf population, including entire packs.

Rabies Vaccine

The long-term problem of habitation degradation will be difficult to solve, according to Haydon.

"Population pressures in these areas are only going to get worse," he said. "Livestock graze higher and in ever greater numbers, and the effect of livestock grazing on the wolf's food supply, the rodents, is largely unexplored at the moment. But it's likely to be serious."

Fatal canid diseases present a more immediate—and more addressable—threat to the wolves.

Wildlife managers have effective rabies vaccines that can address the problem, but there are complications.

Ethiopian wildlife officials have yet to approve the use of oral rabies vaccines, which are cheap, effective, and widely used in Europe and the United States, Haydon says.

As a result, wildlife managers must trap and sedate Ethiopian wolves individually and vaccinate them by hand during rabies outbreaks—an expensive and time-consuming process.

"Practical" Strategy

A further consideration is what immunization strategy to employ. Blanket coverage—immunizing most vulnerable individuals—aims to stamp out a disease entirely.

But the approach is just not practical for Ethiopian wolves, according to the study authors.

"Theoreticians have devoted a lot of effort to working out how to vaccinate populations in ways that prevent epidemics getting started, but this requires coverage that is impractical in wild populations," Haydon said in a press statement.

During the 2003 rabies outbreak, staff with the Ethiopian Wolf Conservation Program and the Frankfurt Zoological Society launched a more targeted vaccination program: Wolves in adjacent mountain valleys were immunized to slow the spread of the disease from infected wolf packs.

The study team plugged extensive population data—some of it gathered during the 1993 and 2003 rabies outbreaks—into ecological and epidemiological models. The researchers' analysis led them to conclude that such targeted immunizations can prevent major die-offs in wild Ethiopian wolves.

"We've looked at vaccination studies that don't prevent all outbreaks but do reduce the chances of really big outbreaks—ones that could push an endangered population over the extinction threshold," Haydon said.

"These strategies turn out to be effective and a lot more practical."

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