Answer:
(From E-Medicine Textbook via Internet:)
Rabies is a viral disease of the central nervous system (CNS), which is widespread throughout the world. It is one of the oldest and most feared diseases reported in the medical literature. Since the control of canine rabies in the 1940’s and 1950’s, human rabies in the United States has become very rare. However, with the recent raccoon rabies epizootic in the United States, as well as high transmissibility of the rabies virus by bats, there continues to be a fear of reemergence of the disease. Most rabies viruses belong to the genus Lyssavirus and the family Rhabdoviridae. They are bullet-shaped RNA viruses with an incubation period of five days to one year, with an average of 20 to 90 days. In some cases the incubation period has been thought to be significantly longer than one year. The virus spreads via retrograde, axoplasmic flow at eight to 20 mm/day, until it reaches the spinal cord and paresthesias at the wound site begin. The virus continues to spread throughout the CNS. It then undergoes centrifugal spread along the peripheral nerves to the skin, intestine, and into the salivary glands where it is shed in the saliva.
Prodrome:
- Patients have presented to EDs with nonspecific fevers and pharyngitis.
- In most cases it lasts from two to 10 days
- During this period, the initial symptom of pain or paresthesias at the site of bite or scratch begins.
- Fever, headache and anorexia may accompany this.
Neurologic Stage (two to seven days):
- Aphasia
- Incoordination
- Paresis
- Paralysis
- Mental status changes
- Hyperactivity
Late Symptoms:
- Hypotension
- Coma
- Disseminated intravascular coagulation (DIC)
- Cardiac arrhythmias
- Cardiac arrest
- Death
Physical:
- High fevers with rapidly progressive encephalitis is characteristic.
- Myoclonus
- Increased lacrimation
- Hypersalivation
- Agitation
- Anxiety
The treatment of human rabies is supportive and often involves therapy for other possible etiologies before the specific diagnosis is made, usually postmortem or well into an ICU stay.
Immediate therapy consists of thoroughly washing off all bite and scratch wounds with soap and water and/or 2% benzalkonium chloride. Wound care should be given as needed. Tetanus prophylaxis is indicated, as are measures to prevent bacterial infection when warranted. A decision must then be made regarding post-exposure prophylaxis.
Post-Exposure Rabies Prophylaxis:
All unprovoked animal attacks are considered high risk for rabies.
If a bite or mucus membrane contact was inflicted by a domestic animal with
known vaccination status, and the owner can quarantine the animal for 10 days,
post-exposure prophylaxis can be withheld.
If signs of rabies occur, the animal should be sacrificed and the head shipped to
a qualified facility for testing, as described above. The regional poison control
center as well as local and regional veterinarians are valuable resources regarding testing
sites and procedures.
If captured, the animal should be killed and the head shipped to a qualified
facility for testing, as described above.
Exposures from small rodents and lagomorphs (squirrels, hamsters, guinea pigs,
gerbils, chipmunks, rats, mice, rabbits and hares) do not require treatment.
These animals can be infected with rabies virus in the lab but have never been
associated with transmission to humans.
This does not include high-risk animals, such as bats, raccoons, foxes, skunks,
woodchucks, non-domestic dogs, or dogs near the Mexican border. In these
cases treatment should be instituted immediately.
Data on bats suggest that insignificant contact with them may result in viral
transmission. Post-exposure prophylaxis for bats is now recommended even in
the absence of a bite or scratch.
Human rabies immunoglobulin and vaccine are recommended for bites and
exposures regardless of the period between exposure and treatment, unless
someone is previously vaccinated and rabies antibodies can be detected. The
average U.S. delay between exposure and treatment is five days, which does not
appear to compromise successful prophylaxis.
Three rabies vaccines are currently available in the U.S., the Human Diploid Cell
Vaccine (HDCV; Imovax), rabies vaccine adsorbed (RVA), and RabAvert
(rabies vaccine produced by Chiron). They are equal in efficacy and safety.
The vaccine takes seven to 10 days to induce an active immune response with
immunity lasting for approximately two years. The vaccine should be
administered in the deltoid region. The dose is 1.0 ml on days 0, 3, 7, 14 and
28.
Passive immunization with human rabies immunoglobulin (HRIG, Hyperab) gives
immediate protection with a serum half-life of 21 days.
Rabies immunoglobulin, 20 IU/kg, should be administered with as much of the
dose as possible infiltrated in and around the wound (if the wound location
allows) and the rest intramuscularly in the gluteal region, using a needle long
enough to ensure IM injection. Different syringes and needles should be used for
the vaccine and the immune globulin.
NOT PREVIOUSLY VACCINATED:
HRIG, 20 I/U per kg body weight (as much as possible infiltrated into and
around site of wound, the rest given IM at a site remote from vaccine injection site)
AND
HDCV 1.0 ml or RVA 1.0 ml IM (deltoid) on days 0, 3, 7, 14 and 28
PREVIOUSLY VACCINATED:
No immune globulin if previous antibody response is documented (otherwise
give HRIG as above)
HDCV or RVA 1.0 ml given IM (deltoid) on days 0 and 3
Mortality/Morbidity: Although rabies is considered to be a uniformly fatal disease, three
cases of survival were reported in the 1970's. No further cases have been reported in the
1980's and 1990's. These three cases involved patients who were given the duck embryo
vaccine or the suckling mouse brain vaccine before the onset of clinical symptoms. Three
additional cases of survival were reported in the 1940's, 1950's, and 1960's, which were not
clearly documented.