Rabies
What is it?
Rabies is a viral infection of the central
nervous system, which means it affects the brain,
spinal cord, and their surrounding membranes. A
person with rabies has difficulty drinking because
the salivary glands are also affected. For this
reason, rabies is sometimes referred to as
hydrophobia, which means fear of water.
Who gets it?
Anyone who is bitten by an animal infected with
the rabies virus can get rabies. People whose work
involves frequent contact with wildlife or
domestic animals that are not immunized are at a
greater risk for getting rabies. These include
veterinarians, animal trainers, animal
exterminators, farm workers, ranchers, forest
rangers, and cave explorers.
What causes it?
Rabies is caused by the rod- or bullet-shaped
Rhabdoviridae. People are infected with this virus
when bitten by an infected animal. The virus
spreads from the saliva of the animal, along the
nerves, to the spinal cord and brain (the central
nervous system). It multiplies in the central
nervous system, and then travels down nerves to
the salivary glands and into the saliva. While
most cases of rabies are transmitted by a bite
from an infected animal, it can also be
transmitted if the infected animal licks you
around an open wound, or mucous membranes such as
the eyes, nose, or mouth. It is also believed that
the virus can be gotten by breathing the infected
air in a bat-infested cave. Because of the
widespread use of the rabies vaccine for pets in
the United States, today most cases of rabies are
transmitted by wild animals such as bats, foxes,
raccoons, skunks, coyotes, and wolves.
What are the symptoms?
The rabies virus can cause no symptoms for
weeks to months after infection as the virus works
its way to the brain. Symptoms usually begin
within 30 to 50 days after infection. Early
symptoms are similar to a cold or flu, and include
muscle pain, headache, fever, nausea and vomiting,
diarrhea, and restlessness. However, as brain
function is affected, the symptoms quickly worsen
to include uncontrollable excitement; loss of
muscle control and other bodily functions; muscle
spasms or paralysis, usually beginning in the
lower legs; agitation and irritability;
depression; and confusion. When the virus affects
the nerves of the salivary glands, it causes
painful spasms of the throat and voice box. Trying
to take a drink of water can trigger these spasms,
so a person with rabies may not be able to drink.
The infected salivary glands also produce too much
saliva, which causes the appearance of foaming
around the mouth that is characteristic of rabies.
Severe symptoms are followed by coma and death,
usually within 3 to 20 days of the onset of these
symptoms.
How is it diagnosed?
Because rabies must be treated before the
infection reaches the brain, a time during which
the patient is symptom-free, it's important to act
quickly to make a diagnosis and begin treatment.
So, any time a person is bitten by a wild or
domestic animal, the first step is to find the
animal that caused the bite. If the animal is a
pet that has had rabies shots, the animal is
observed by a veterinarian or other specialist in
animal control for signs of rabies for 10 days. If
the animal is a pet that has not had rabies shots,
the pet is confined to a cage by itself
(quarantined) and observed for signs of rabies. If
you have been bitten by a pet or wild animal that
is showing signs of rabies, the animal is killed
so its brain tissue can be examined for the rabies
virus. Once symptoms begin, your doctor can
perform blood tests and a test of your
cerebrospinal fluid (CSF), called a lumbar
puncture, to rule out any other causes of your
symptoms. A lumbar puncture involves inserting a
needle into the area around the spinal cord to
withdraw a sample of CSF. The area is first numbed
so you feel as little discomfort as possible.
Rabies can be diagnosed after symptoms have begun
with a test called a fluorescent antibody test.
This test involves taking a sample of skin (called
a biopsy), usually from the back of the neck, and
treating it with a fluorescent dye. The dye binds
with the antibodies produced by the body in
response to the rabies virus, making the virus
visible under a microscope. The virus can also be
seen by testing the infected patient's saliva, or
by testing the fluid around the cornea of the eye
for the virus.
What is the treatment?
If the rabies virus is treated immediately, it
can be killed before it infects the brain and
causes any symptoms. Whenever a person is bitten
by an animal, wild or domestic, you should
thoroughly wash the bite and the area around it
with antibiotic soap and water and seek medical
treatment. Your doctor may give you a tetanus shot
and antibiotics, to prevent infection, and will
file a complete report on the animal that bit you.
If you were bitten by an animal that is up-to-date
with rabies shots, and there is no illness
observed in the animal, you will need no
additional treatment. If the animal that bit you
is suspected of having rabies; has not been found,
but is likely to have rabies; or has been
diagnosed with rabies, you will be treated with
injections of the rabies vaccine, called RIG
(rabies immune globulin). Half of this dose is
given at the location of the bite and the other
half is injected into a muscle, usually around the
hip.
A series of five shots are given over a period
of 28 days. The first shot is given the day you
are determined to be at risk for the rabies virus,
and the remaining shots are given on days 3, 7,
14, and 28. If, during that time, it is found that
the animal does not have rabies, the shots can be
stopped. Once the virus has reached the brain,
however, treatment centers around keeping the
patient comfortable by relieving pain from muscle
spasms, preventing seizures, and relieving
anxiety. As symptoms progress, life supporting
measures may need to be taken. However, once the
virus has infected the central nervous system,
there is no cure and the infection is usually
fatal.
Self-care tips
Preventing rabies is easy. Make sure any pets
receive their rabies shots on a regular basis and
report any stray animals around your house. Avoid
getting close to unknown stray animals, as well as
wild animals. Make sure all your windows and doors
are screened to prevent animals from entering your
home. Not all animals with rabies have the
telltale signs of rabies (aggressive behavior,
obvious confusion, foaming at the mouth). When
animals that are normally nocturnal, which are
those that sleep during the day and come out at
night, are active during the day, you should be
suspicious. Nocturnal animals that are more likely
to carry rabies include raccoons, bats, skunks,
wolves, and foxes. If you think you may have been
exposed to rabies by a bite or lick from an
infected animal, seek medical attention
immediately. There is time to prevent a fatal
infection if you are treated as soon as possible.
If your job puts you at risk for rabies, ask your
doctor about a vaccine that will help prevent the
infection in case you are bitten. If your pet has
contact with an animal that might be infected,
wear rubber gloves when handling your pet and call
your veterinarian. Rabies is more common in some
countries, such as parts of Mexico, El Salvador,
Colombia, the Philippines, Vietnam, and India. If
you are traveling in such a country, you may want
to consider rabies vaccination before you travel.
This information has been designed as a comprehensive and quick reference
guide written by our health care reviewers. The health information written
by our authors is intended to be a supplement to the care provided by your
physician. It is not intended nor implied to be a substitute for
professional medical advice.
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