Table of Contents
Introduction
 The
history of rabies goes back to 2000 B.C. Aristotle recognized
that dogs were able to transmit the infection to other dogs
through bites. When a 9-year-old boy was bitten by a rabid
dog in 1885, Louis Pasteur treated him with a rabid spinal
cord vaccine, becoming the first human being successfully
immunized, as the boy did not develop rabies.
Rabies is a virus that ranks 10th in causes of mortality
in the world. There are approximately 55,000 deaths annually.
The vast majority of these are clearly in Third World countries.
Rabies Virus
The rabies virus contains 5 proteins. The virus is almost
always transmitted by the bite of an infected animal, most
commonly wild and domestic carnivores. There are some activities,
especially cave explorers, who are more likely to come in
contact with the virus, actually breathing in the virus in
the dark, humid cave environment where a large number of infected
bats are found. The virus is able to survive outside the host.
Carnivorous animals can acquire rabies by eating infected
prey and skunks have been able to transmit rabies to their
young transplacentally, and there is one reported human case,
where the mother was dying of rabies, and transmitted rabies
to her unborn child.
Rabies is primarily a disease of animals. Infected dogs account
for less than 5% of all rabies cases. However in other countries
where canine rabies has not been controlled, it accounts for
90% or more of cases of rabies. In North America, especially
on the east coast, an increasing number of infected raccoons
are being seen. In the Midwest, skunks and bats more commonly
carry rabies.
Wild animals generally account for about 93% of rabies, raccoons
about 40% of that, skunks 30%, and foxes 6%.
It should be noted that the following animals have rarely
been found to carry rabies, and almost never require post-exposure
prophylaxis injections. These are squirrels, hamsters, guinea
pigs, gerbils, chipmunks, rats, mice, domesticated rabbits
and other small rodents.
Rabies is considered to be uniformly fatal. However, there
have been some cases of spontaneous recovery, although very
rare.
Rabies Symptoms
When an individual is first bitten by a rabid animal, the
symptoms are first seen in the skeletal muscle. It travels
along the neuromuscular spindles and on the peripheral nerves
to the central nervous system. An average incubation period,
from the time of the bite to the time symptoms present, is
about 60 days. That is specifically a bite that was obtained
on the foot. A bite on the face only takes about 30 days.
It should be noted that approximately half of untreated individuals
bitten by rabid dogs are going to develop rabies. This seems
to be a combination of a couple factors, the bite location,
and the amount of inoculum or saliva that is contaminated.
So the incubation period can vary, anywhere from 9 days up
to a year, although both 9-days and a year are rare. Again,
it depends on the bite site and the amount of inoculum. The
vast majority of the cases are being 2 weeks and 3 months.
Symptoms are usually vague and include fatigue, muscle aches,
anxiety, irritability, agitation, insomnia, headache, nausea,
vomiting and abdominal pain. One of the true early symptoms
is pain and itchiness as well as numbness at the bite site,
which occurs in about 55-60% of patients. It is not uncommon
for humans to have what is called furious rabies, and these
individuals have episodes of agitation. They can have seizures,
can thrash out and become very aggressive. They may have severe
pharyngeal spasms and become very thirsty, the combination
is no doubt what causes the excessive salivating and drooling
that occurs.
When untreated, a human being only survives approximately
8 days. With supportive care, life can be extended up to a
month.
Rabies Vaccine
Pre-exposure Immunization: It is strongly
recommended that individuals at high recreational or occupational
risk be vaccinated. Individuals in professions of greatest
risk are taxidermists, wildlife biologists, and professional
or recreational trappers, especially those individuals traveling
to Third World countries, where frequently infected domesticated
animals are seen. The CDC recommends vaccination if traveling
in Third World countries for longer than 30 days. Please check
with your healthcare provider regarding countries you may
be traveling to, or if your job or recreational activity places
you at greater risk.
Rabies Treatment
Post-exposure Prophylaxis: Any wild animal
that bites a person should be killed immediately, and the
brain sent for diagnostic evaluation. Even though the animal
may not appear ill, it should be noted that some of these
animals that are infected could shed the virus for up to 2
weeks before they even show that they are ill with the rabies
virus. According to Auerbach, unvaccinated dogs and cats that
are bitten by a rabid animal should be destroyed immediately.
If the owner refuses to have this done, the unvaccinated animal
“should be kept in strict isolation for 6 months, and
vaccinated one month before being released.”
A good history should be obtained:
- Whether the bite was provoked or unprovoked.
- Bites to the face and hands carry the highest risk.
- A fully vaccinated dog or cat is unlikely to become infected
with rabies, although some rare cases have been reported,
especially when they only got a single dose and did not
have the complete regimen.
The CDC recommends that a healthy dog, cat or ferret that
bites a person should be confined and observed for 10 days.
In the United States, post-exposure prophylaxis consists
of the following: One dose of HRIG (Human Rabies Immune Globulin),
and then 5 doses of the rabies vaccine over a 28-day period.
The first dose, the HRIG, should be given as soon as possible
after exposure, preferably within 24-hours. It should be important
to note that the CDC recommends that as much as possible the
full-dose be infiltrated around the wound. HRIG should never
be administered in the same syringe or into the same anatomical
site as the vaccine. They also recommend that post-exposure
prophylaxis be followed exactly how the guidelines are stated.
After your initial dose of HRIG, the 5 doses of vaccine should
be given on days 0, 3, 7, 14, and 28, and it is 1 ml. dose
per vaccine. Again, as stated previously, it should not be
given in the same syringe or in the same site where the HRIG
was given. They also recommend that it not be given in the
gluteal region, since the vaccine might be deposited in fat
and poorly absorbed. They recommend the deltoid muscle.
For further information on rabies treatment, Survive Outdoors
strongly recommends that you visit www.cdc.gov.
References
1. Paul S. Auerbach, Wilderness
Medicine
2. Tintinalli, Judith, Kelen, Gabor, Stapczynski, Stephen,
J., Emergency Medicine, A Comprehensive
Study
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