Media exaggerated threat of rabies strain that jumped species, epidemiologist says
Bat rabies strikes foxes and skunks in Arizona
June 10, 2009 (published)
The threat from the new-variant rabies virus that has infected foxes and skunks in the area surrounding Flagstaff, Ariz., appears to have been greatly exaggerated.
There is a very serious outbreak of rabies in Arizona, however.
In early May, National Geographic News reported that a new rabies virus was spreading fast across Arizona, and worst of all, animals seemed to be “able to pass the virus on to their kin — not just through biting and scratching but through simple socializing, as humans might spread a flu."
That report prompted a slew of frantic phone calls to the state’s Department of Health Services. People wanted to know if the virus was going to be spreading from person to person in the ambient air or by handshakes.
None of that is true, according to Craig Levy, an epidemiologist and program manager with the Department’s Vector-Borne and Zoonotic Disease Program.
The new variant originated with big brown bats. The virus initially was noted in another species, a skunk, in 2001. Now the virus has crossed to, and infected, a number of other mammalian species, and what is remarkable is that it has mutated so that those species can pass it among themselves. Historically, as rabies virus variants adapt to specific host species, passage to a different species, such as from a bat to a mammal such as a fox or skunk, is a dead-end transmission. That is, the likelihood of the fox or skunk transmitting the virus to other mammals in a sustained manner is low. The variants now occurring in foxes and skunks in Arizona, however, have evolved relatively rapidly to allow continued transmission among these animal species.
Such a development has researchers giddy because this kind of evolution in a rabies virus has never before occurred in the era of surveillance and molecular biology, under the watchful eye of science.
But the virus is no more transmissible or virulent than any other rabies variant, Levy says.
“It seems one media story begets another,” he says. The virus “is not more infectious or transmissible.”
The notion that this variant virus might travel in the wind appears to have arisen when a state official said it can be passed by “casual contact." The official meant that the virus could be passed on without a scratch or a bite, or rather if a rabid fox or skunk licked another on its nose or some other mucous membrane, Levy explains.
That's true for any rabies strain.
Arizona does appear to be headed toward a record number of rabies cases this year. At the end of May, the number of rabies cases identified totaled 130, compared to only 76 cases tallied during the same time last year. Infections were confirmed in 69 skunks, 36 foxes and 15 bats.
But the increase has nothing to do with the variant strain. Rather, it probably is related to wild animal populations, Levy says. The virus now appears to be spreading through the area's fox population. In addition, Flagstaff’s growth in recent years has also impacted the spread by actually facilitating congregation of bats, skunks and foxes in these habitats. These species live close to people, and spread to humans is a concern. However, this variant is no more contagious than any other rabies virus — it still requires contact with infected saliva. The unique aspect of this variant is its relative rapid adaptation to new host species.
So far the cases of variant virus have been located only around Flagstaff and Coconino County, in the northern part of the state. But Coconino is not the county with the most cases this year. Pima County, nearly 300 miles south, reports 47 cases of rabies in animals while Coconino has had 22 cases.
Officials say public distress has been fueled, in part, by a number of wild and outlandish incidents, starting with the March 2008 attack by a rabid mountain lion on a 10-year-old boy in a campsite north of Phoenix.
Last November, an encounter with a rabid fox garnered national headlines and a trip to the Late Show with David Letterman for the woman involved. Michelle Felicetta was jogging on a trail in Prescott when she encountered a fox standing in her way. As she backed up slowly, the fox attacked and bit her on her toe. She grabbed the fox by the neck before it could bite her on the knee, but the fox thrashed and latched down on her arm and would not let go.
Felicetta surmised that the fox was rabid, so she decided she could not let it get away and cooly ran a mile back to her car, with the fox still clinging to her arm. Then she threw the fox, still alive but more docile, into the trunk and drove to an emergency room.
In March, three patrons left the Chaparral, a neighborhood bar in Cottonwood. Seconds later they all scampered back in, followed by a ferocious bobcat. Pandemonium ensued, with customers scrambling up on tables and stools. Two customers were bitten or scratched. The bobcat departed and later was shot in a parking lot by police.
Earlier, the same bobcat had scratched a woman who thought she had hit it with her car. It also menaced a Pizza Hut employee outside the restaurant.
The bobcat did have rabies, but not the big-brown-bat variant, Levy says.
The increase in the number of new rabies cases is expected to calm eventually, Levy says. In the meantime Coconino County has imposed a rabies quarantine that requires owners to keep cats inside and dogs on leashes, or risk having their pets impounded.
Many residents are nervous.
“I live at the foot of Mt. Elden,” says Zoe Senese, a receptionist at the Coconino Animal Hospital. “I used to go hiking up there all the time. Now I don’t go at all.”
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