Rabies vaccine may save rarest wolf from extinction

One of the rarest animals in the world might be saved from imminent extinction with the help of a rabies vaccine targeted at the most vulnerable members of the species.

There are no more than about 500 Ethiopian wolves left alive and up to three-quarters of the population were wiped out in a rabies outbreak in 2003. This led scientists to experiment with a targeted vaccination campaign that they believe could save the species from dying out completely in any future rabies outbreaks.

A computer model of the vaccination following the 2003 epidemic suggests that the campaign has worked and that the short-term future of the wolf now looks more secure, according to a study published in the journal Nature. "Ethiopian wolves are the rarest carnivores in the world, restricted to a few mountain enclaves in the Ethiopian highlands," said Claudio Sillero-Zubiri, of Oxford University's Wildlife Conservation Research Unit.

The wolf is a specialist carnivore feeding on the rodents that live in the high alpine pastures. There are six breeding populations living in the Ethiopian highlands and all of them are susceptible to infections introduced by the domestic dogs of local shepherds. "Canid diseases, such as rabies and distemper transmitted from domestic dogs, pose the most immediate threat to their persistence, and targeted vaccination intervention presents a useful tool to protect the remaining small wolf populations from extinction," Dr Sillero-Zubiri said.

Ethiopian wolves live in some of most inaccessible mountain enclaves of the world and it is difficult to reach some of the remoter packs and capture all their members, he said. As a result it was thought that it would be impossible to carry out the sort of blanket vaccination that was deemed necessary for an effective campaign against the rabies virus.

But the study showed that instead of vaccinating almost every animal, the scientists could get away with inoculating just 30 per cent of the population under the greatest threat of coming into contact with domestic dogs. The modelling study demonstrated that even if rabies outbreaks became more frequent, fewer wolves would need to be vaccinated than under a wholesale vaccine programme in order to virtually eliminate the extinction threat posed by such outbreaks, Dr Sillero-Zubiri said.

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

In the study, 80 wolves were captured and vaccinated. They formed part of the largest breedinggroup of 350 wolves in the Bale Mountains, in the south-east Ethiopian highlands. Dr Sillero-Zubiri said that the wolf still faces long-term threats from climate change and habitat loss, which is driving the remaining populations to higher altitudes. The Oxford team has been working on the preservation of the Ethiopian wolf for 20 years and the scientists work closely with local people and the government.

Karen Laurenson, a member of the research team from Edinburgh University, said: "The vaccination of wildlife, when appropriate and strategically used, is a safe, direct and effective method of reducing extinction threats."

It is hoped that the further development of oral rabies vaccines that can be given in food will in future make it easier to vaccinate the remote wolf populations.