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Health News
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Rabies
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Rabies
(from Latin rabere; to rage) is an acute infectious
disease of the central nervous system caused by a Rhabdo
virus. It generally persists in nature as a salivary gland
infection of carnivorous animals. The virus is usually
transmitted from animal to animal and from animal to man
by a bite (exposure). It is also possible, but quite rare,
that people may get rabies if infectious material from
a rabid animal, such as saliva, gets into their eyes,
nose, mouth, or a wound. The vast majority of rabies cases
reported to the Centers for Disease Control and Prevention
(CDC) each year occur in wild animals like raccoons, skunks,
bats, and foxes. Domestic animals account for less than
10% of the reported cases, with cats, cattle, and dogs
most often reported rabid. However, all warm-blooded animals
are susceptible.
Rabies virus infects the
central nervous system, causing encephalopathy and ultimately
death. Symptoms of rabies in humans are initially nonspecific,
consisting of fever, headache, and general malaise. As
the disease progresses, neurological symptoms appear and
may include insomnia, anxiety, confusion, slight or partial
paralysis, excitation, hallucinations, agitation, hypersalivation,
difficulty swallowing and hydrophobia (fear of water).
Death usually occurs within days of the onset of symptoms.
Rabies has been identified
in the contiguous United States, Alaska, the District
of Columbia and Puerto Rico. In 1997, (the most recent
nationwide data) rabies was reported in all states except
Hawaii. In 1997, 93% of the rabies cases that occurred
were in wild animals (7,899 animals). Rabies was recorded
in 13 species of terrestrial wildlife and in insectivorous
bats. Cases in the major wildlife hosts (raccoons 51%,
skunks 24%, bats 11%, and foxes 5%) accounted for 91%
of all reported rabies cases.
In the U.S., rabies in
terrestrial mammals can be linked to distinct virus strains.
Each strain is maintained primarily by intraspecies (within
species) transmission although spillover infection of
other species may occur. Nationwide there is one strain
in raccoons that has been identified in 19 states and
the District of Columbia; 3 skunk-strains; 4 fox-strains
and 1 coyote-strain in Texas. Bat rabies has had distinct
strains identified but geographic boundaries cannot be
defined.
Small rodents (e.g., squirrels,
hamsters, guinea pigs, gerbils, chipmunks, rats, and mice)
and lagomorphs (including rabbits and hares) are almost
never found to be infected with rabies and have not been
known to transmit rabies to humans. Bites by these animals
are usually not considered a risk of rabies unless the
animal was sick or behaving in any unusual manner and
rabies is widespread in your area. From 1990 through 1996,
in areas of the country where raccoon rabies was widespread,
woodchucks accounted for 93% of the cases of rabies among
rodents reported.
From numerous studies conducted
on rabid dogs, cats, and ferrets, we know that rabies
virus inoculated into a muscle travels from the site of
the inoculation to the brain by moving within nerves.
The animal does not appear ill during this time, which
is called the incubation period and which may last for
weeks to months. A bite by the animal during the incubation
period does not carry a risk of rabies because the virus
is not in saliva. Only late in the disease, after the
virus has reached the brain and multiplied there to cause
encephalitis (or inflammation of the brain), does the
virus move from the brain to the salivary glands and saliva.
Also at this time, after the virus has multiplied in the
brain, almost all animals begin to show the first sign
of rabies. Most of these signs are obvious to even an
untrained observer, but within a short period of time,
usually within 3 to 5 days, the virus has caused enough
damage to the brain that the animal begins to show unmistakable
signs of rabies.
An important consideration
in reaching a clinical (direct observation) diagnosis
of rabies in animals, especially wild ones, is that no
sign (or series of signs) is typical or characteristic.
Signs of other diseases such as distemper, hepatitis,
listeriosis, tetanus, botulism and some parasitic diseases
are similar to those of rabies. Plant or chemical toxins
can also cause encephalitic syndromes. These clinical
signs are so varied and overlapping that limited confidence
should be placed on a clinical diagnosis of rabies. The
only sure way to diagnose rabies is with laboratory tests.
People usually get exposed
to rabies through the bite of a rabid animal. It is also
possible, but quite rare, that people may get rabies if
infectious material from a rabid animal, such as saliva,
gets into their eyes, nose, mouth, or a wound. Direct
exposure to scratches, abrasions, open wounds, or mucous
membranes contaminated with saliva or other potentially
infectious material (such as brain tissue) from a rabid
animal constitute a nonbite exposure and should be considered
potentially infectious. Any person or animal bitten or
scratched by either a wild, carnivorous mammal or a bat
that is not available for testing should be regarded as
having been exposed to rabies.
Prevention and Control
There is no treatment for
rabies after symptoms of the disease appears. At this
point the disease is considered fatal. However, two decades
ago scientists developed an extremely effective new rabies
vaccine regimen that provides immunity to rabies when
administered after an exposure (postexposure prophylaxis)
or for protection before an exposure occurs (preexposure
prophylaxis). Although rabies among humans is rare in
the United States, every year an estimated 18,000 people
receive rabies preexposure prophylaxis and an additional
40,000 receive postexposure proprophylaxis.
Preexposure prophylaxis
Preexposure vaccination
is recommended for persons in high-risk groups, such as
veterinarians, animal handlers, and certain laboratory
workers. Other persons whose activities bring them into
frequent contact with rabies virus or potentially rabid
bats, raccoons, skunks, cats, dogs, or other species at
risk of having rabies should also be considered for preexposure
prophylaxis.
Preexposure prophylaxis
is given for several reasons. First, although preexposure
vaccination does not eliminate the need for additional
medical attention after a rabies exposure, it simplifies
therapy by eliminating the need for human rabies globulin
(HRIG) and decreasing the number of vaccine doses needed.
Second, it may enhance immunity in persons whose postexposure
therapy might be delayed. Finally, it may provide protection
to persons with inapparent exposures to rabies.
Preexposure booster doses
of vaccine should be administered on a periodic basis.
High-risk groups such as people who work in research facilities
should have a serum sample tested for rabies antibody
every 6 months. The frequent-risk category includes other
laboratory workers, spelunkers, (taxidermists), veterinarians
and staff, and wildlife officers in areas where rabies
is enzootic (constantly present). Person in this group
should have a serum sample tested for rabies antibody
every 2 years.
Postexposure prophylaxis
Postexposure prophylaxis
(PEP) is indicated for persons possibly exposed to a rabid
animal. Possible exposures include animal bites, or mucus
membrane contamination with infectious tissue, such as
saliva. PEP should begin as soon as possible after an
exposure. There have been no vaccine failures in the United
States when PEP was given promptly and appropriately after
an exposure.
Administration of rabies
PEP is a medical urgency, not a medical emergency. Physicians
should evaluate each possible exposure to rabies and as
necessary consult with local or state public health officials
regarding the need for rabies prophylaxis.
In the United States, PEP
consists of a regimen of one dose of immune globulin and
five doses of rabies vaccine over a 28-day period. Rabies
immune globulin and the first dose of rabies vaccine should
be given as soon as possible after exposure. Current vaccines
are relatively painless and are given in your arm, like
a flu or tetanus vaccine.
What to do after a possible exposure
If you are exposed to a
potentially rabid animal, wash the wound thoroughly with
soap and water, and seek medical attention immediately.
What can be done in the taxidermy studio to prevent
exposure
The most obvious way is
to wear gloves. Non-sterile examination gloves come in
a variety of sizes, are waterproof, and relatively cheap.
They are thin enough that you can "feel" through them
well enough to perform almost every task. Gloves will
minimize the chance that potentially infected animal tissue,
body fluids, and with rabies, saliva from touching cuts
we all have on our hands most of the time.
Washing your hand after
working on an animal, even if you wear gloves, is a good
practice to follow. Plain soap and warm water is adequate
for this purpose. If you wish, you could use an iodine-containing
soap or any other bactericidal or bacteristatic soaps.
One of the easiest rules
to follow is to never put anything in your mouth in the
work area. This includes food, drinks, cigarettes, tools,
or your fingers.
Each day after work, you
should clean your work area, tools and instruments with
a bactericidal solution such as Clorox and water. The
solution should be left on the tabletop and your instruments
for several minutes before wiping clean.
Other than examination
gloves, two more protective devices you may consider using,
depending upon what job you are performing, are glasses
and a surgical type mask. Remember two ways for rabies
or other infectious diseases to enter your system are
through your eyes and the respiratory system.
In areas where rabies is
common or epidemic, it would be a good precautionary measure
for taxidermists to get a pre-exposure vaccine. It is
simple to do and can ease your mind and make life much
easier if you do encounter a potential exposure later.
The biggest thing to remember
when dealing with potentially rabid animals is to treat
them as being potentially rabid. Use common sense, don't
take careless chances and if a potential exposure occurs
take immediate appropriate action. Remember, when you
show signs of rabies it is too late to do anything. It
is your health, take care of it. |
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