- Bites from tiny bats cause almost all cases of rabies
in people in the US, according to a new analysis. The infected bats can
weigh just ten grams and their bite can easily be mistaken for a thorn
prick or bee sting.
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- "Worldwide, bat transmission of rabies is the tip
of the iceberg. But in the US human cases of rabies are very rare now,
which is why we're interested in this route," says Robert Gibbons
of the Walter Reed Army Institute of Research in Silver Spring, US.
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- Gibbons reviewed the 26 human deaths from rabies acquired
in the US over the past decade. Blood tests revealed that 24 of these were
from a subtype of the virus that infects bats. But only two of these people
reported being bitten by a bat.
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- "People thought perhaps it spread through the air,
or a bat bit a cat and the person caught rabies from the cat," Gibbons
says. But a closer examination of the cases revealed that direct contact
with a bat was probably responsible for each transmission.
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- For example, an engineer who visited caves in the US
to evaluate their suitability for guano mining denied any bat bites after
he developed symptoms of rabies. But his case history reveals that he did
have a bleeding lesion on his face when leaving the cave, Gibbons says.
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- Swarming mites
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- Indigenous rabid bats have been reported in every mainland
US state, except Hawaii. The most common bats in the US, the silver-haired
and eastern pipistrelle bats, weigh up to about ten grams and have jaws
less than one centimetre across. These bats are often found alone in trees,
foliage and crevices in wood and rock.
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- Rabies prophylaxis is 100 per cent effective if given
before symptoms appear. "But symptoms are generally a death sentence,"
Gibbins says. Only about one per cent of US bats are probably infected
with rabies, but anyone bitten by a bat should seek immediate vaccine treatment,
he says.
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- Worldwide, about 50,000 people die from rabies each year.
Most of these deaths are in Africa and Asia, where canine rabies is common
and the majority of deaths follow bites from infected dogs.
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- Gregory Moran at the Division of Infectious Diseases
at the Olive View-UCLA Medical Center in California, says: "Many issues
related to rabies transmission from bats need further study." But
direct research in bat caves is unpleasant, he adds. "Few researchers
would be willing to brave the rain of bat urine, pools of guano and swarming
mites."
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- Journal reference: Annals of Emergency Medicine (vol
39, p 528)
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- http://www.newscientist.com/news/news.jsp?id=ns99992243
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