10.21 Rabies Prophylaxis
A possibly contagious animal has bitten the patient, or the
animal's saliva, brain tissue or cerebrospinal fluid contaminated an abrasion or mucous
What to do:
- Clean and debride the wound thoroughly. Irrigate with soap
and water or 1% benzalkonium chloride and rinse with norma
- Know the local prevalence of rabies, or ask someone who
knows (e.g., local health department).
- If the offending animal was an apparently healthy dog or
cat, arrange to have the animal observed for ten days. During
that period, an animal affected with rabies will show symptoms
and should be sacrificed and examined for rabies using a
fluorescent rabies antibody (FRA) technique. If the test is
positive, begin prophylaxis with rabies immune globulin and human
diploid cell vaccine. If the animal is not available for
observation, the decision of whether to provide rabies
prophylaxis depends on the local prevalence of rabies in domestic
animals, rodents, and lagomorphs.
- If a wild animal (e.g., bat, bobcat, coyote, fox, opossum, raccoon,
skunk) capable of transmitting rabies is caught, it should be
killed, placed on ice and sent to the local public health department so the
brain can be examined with immunofluorescence. If the animal did
not appear to be healthy, or if the bite is on the patient's
face, the patient should be started on RIG and HDCV in the
meantime and stopped only if the test is negative.
- If the offending wild animal was not captured, no matter how
normal-appearing, assume it was rabid, and give a full course of
RIG and HDCV.
- Provide rapid passive immunity with 20 IU/kg of rabies immune
globulin, half im and half infiltrating the area of the bite. This passive protection has a half-life of 21 days.
- Begin rapid immunization with human diploid cell vaccine,
- Make arrangements for repeat doses of HDCV at 3, 7, 14, and
28 days post exposure.
What not to do:
- Do not treat the bites of rodents and lagomorphs (hamsters,
rabbits, squirrels, rats, etc.) unless rabies is endemic in your
area. As of 1996, rodent and lagomorph bites have not caused
human rabies in the United States.
- Do not treat exposures where contact was limited to petting a rabid animal or where these was only contact with the animal's blood, urine, feces or skunk spray.
- Do not omit rabies immune globulin. Treatment failures have
resulted from giving HDCV alone.
The older duck embryo vaccine for rabies required 21
injections, and produced more side effects and less of an
antibody response than the new human diploid cell vaccine.
Sometimes, neurological symptoms would arise from DEV
treatment, raising the agonizing question of whether they
represented early signs of rabies or side effects of the
treatment, and thus whether treatment should be continued
or discontinued. It is much easier nowadays to initiate
immunization with HDCV and follow through, because side
effects are minimal and antibody response excellent. Roughly 25% of patients experience redness, tenderness and itching around the injection site and another 20% experience headaches, myalgia or nausea.
Patients with an immunosupressive illness or those taking corticosteroids, immunosupressive agents or antimalarial drugs may have an inadequate immune response to vaccination, and should have assays of serum antibodies. Pregnancy is not a contraindication to postexposure prophylaxis.
The incubation period of rabies varies from weeks to months
roughly in proportion to the length of the axons up which
the virus must propagate to the brain, which is why
prophylaxis is especially urgent in facial bites.
- Kauffman FH, Goldmann BJ: Rabies Am J Emerg Med 1986;4:525-
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Craig Feied, MD
Mark Smith, MD
Jon Handler, MD
Michael Gillam, MD