How does rabies keep a permanent presence in Alaska? Maybe with the help of arctic foxes

Rabies is a death sentence for any animal. Experts have wondered how a virus survives when it kills all the creatures it infects.

"We don't have a really good answer to that," said the University of Alaska Fairbanks' Karsten Hueffer. "It probably has to do with the long incubation time of the virus, which can be months."

Hueffer and his colleagues, including four university undergraduate students, wrote a paper on how the state's arctic foxes might be the carrier that keeps the disease present all the time in the Western Alaska. Red foxes also get infected with rabies and pass it on, but the virus may not endure in their populations. In a future with fewer arctic foxes and more of the dominant red foxes, rabies might wane in Alaska.

[Red foxes move into arctic fox territory on North Slope – with help from people]

Scientists noted a constant presence of rabies virus in the coastal tundra home of the arctic fox. Interior forests inhabited by only the red fox seem to only have sporadic outbreaks of rabies.

The researchers did their genetic testing of arctic and red foxes across Alaska using hundreds of flesh samples from biologists, trappers and museum collectors. Analyzing the genetic makeup of both species, they found that arctic foxes were more closely linked to the virus than red foxes.

[Arctic fox likely evolved from a Himalayan ancestor, study says]

Foxes spread rabies by biting. The virus rides in their saliva and invades other animals through wounds or mucous membranes. After incubation periods that last from eight days to six months, foxes can lose their natural timidity, sometimes attacking dogs and infecting them. Dogs with the virus can spread it to people.

The rabies vaccine can save people, but it has to be taken right after infection. Animals need routine vaccinations to prevent infections. There is no good treatment for rabies and rabid animals become paralyzed and die.

Before the genetic study, scientists thought that rabies perhaps came to Alaska via infected foxes wandering over from Canada or Russia. Strains that walked over the border in foxes might have disappeared in Alaska after a while. But now they think the virus never goes away, living on within infected arctic foxes of Alaska's west coast and the Aleutians.

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Because arctic foxes are adapted to life on and around sea ice, they are facing greater changes than the larger and more dominant red fox. If a shrinking habitat and competition from the red fox greatly reduces arctic fox populations, rabies in Alaska might be reduced along with them.