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Rabies

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Definition

Rabies is a viral infection. It infects the brain and spine. Rabies is almost always fatal unless treated before symptoms appear.
The Nervous System
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Causes

Rabies is caused by a virus. It is found in infected, warm-blooded animals. Animals that commonly carry the virus include:
  • Bats
  • Raccoons
  • Skunks
  • Foxes
  • Coyotes
The virus is in the saliva, brain, or nerve tissue of infected animals. Humans most often contract rabies through a bite or scratch from an infected animal. The virus may also be passed if infected tissue comes into contact with human mucus membranes. This tissue is found in the eyes, nose, or mouth.

Risk Factors

The only risk factor is contact with an infected animal.
In most parts of the US any contact with a bat may be considered a rabies risk factor. Seek medical advice if you find a bat anywhere inside your home.

Symptoms

Symptoms often start within 3-7 weeks. In some cases, the virus can incubate up to one or more years.
Death usually occurs within a week after symptoms appear.
Symptoms in humans may include:
  • Pain, tingling, or itching at the site of the bite wound or other site of viral entry
  • Stiff muscles
  • Increased production of thick saliva
  • Flu-like symptoms, such as headache, fever, fatigue, nausea
  • Painful spasms and contractions of the throat when exposed to water (called hydrophobia)
  • Erratic, excited, or bizarre behavior
  • Paralysis
Symptoms in animals may include:
  • Erratic behavior, often overly aggressive or vicious
  • Disorientation (eg, nocturnal animal such as a bat or fox appearing in daylight)

Diagnosis

If you think you have been exposed to rabies:
  • See a doctor or contact a public health official immediately
If the animal is available and appears well, it will be kept under observation for 10 days. If no symptoms develop, you are not at risk for rabies. If the animal is sick or dead, its head will be shipped to a special facility. There the brain will be examined for the presence of the virus. In the meantime, you may be advised to begin treatment.
If the animal is unavailable, treatment may be given. This could depend on:
  • Animal's species
  • Where the encounter took place
  • Other factors

Treatment

If an animal has bitten you, immediately do the following:
  • Wash the wound immediately with plenty of soap and water. This will remove saliva. It is the most important first step you can take in preventing rabies.
  • Call your doctor or seek care in an emergency room.
If it is likely that you have been exposed to rabies, your doctor will recommend:
  • Postexposure prophylaxis—treatment to prevent illness from developing
This involves two injections:

Human Rabies Immune Globulin (HRIG)

When needed, this is given within 24 hours after exposure. It contains large amounts of antibodies to the rabies virus. In most cases, half of the dose should be injected into the wound and surrounding tissue. The rest is given into a muscle. If you have previously received rabies vaccine, you may not need the HRIG shot.

Other Rabies Vaccines

Rabies vaccines make your immune system create antibodies against the virus. These antibodies will live in your body for many years. There are three types of rabies vaccines available:
  • Human diploid cell vaccine (HDCV)
  • Rabies vaccine adsorbed (RVA)
  • Purified chick embryo cell culture (PCEC)
Your doctor will give you 4-5 shots of one of these vaccines. They will be given over the next four weeks. The vaccine will be injected into your upper arm muscles.
Certain medicine may interfere with your response to the rabies vaccine. Be sure to tell your doctor about all medicine or herbs that you take on a regular basis.

Prevention

To help prevent rabies:
  • Vaccinate house pets.
  • Avoid contact with wild animals.
  • Do not touch any wild animal. Avoid it even if it appears to be dead.
  • Seal basement, porch, and attic openings. This will prevent an animal from entering your home.
  • Report any animal to your local animal control if it is acting strange or appears sick.
  • If you often come in contact with potentially rabid animals, get the rabies vaccine before exposure. Booster doses are often needed.

RESOURCES

Centers for Disease Control and Prevention (CDC) http://www.cdc.gov/

National Institute of Allergy and Infectious Diseases http://www.niaid.nih.gov/

CANADIAN RESOURCES

Public Health Agency of Canada http://www.phac-aspc.gc.ca/

Safe Canada http://www.safecanada.ca/

References

Hankins DG and Rosekrans JA. Overview, prevention, and treatment of rabies. Mayo Clin Proc . 2004;79(5):671-676.

Rabies. Centers for Disease Control and Prevention website. Available at: http://www.cdc.gov/ncidod/dvrd/rabies . Accessed October 14, 2005.

Rabies. DynaMed website. Available at: http://www.ebscohost.com/dynamed/what.php . Accessed October 14, 2005.

3/26/2010 DynaMed's Systematic Literature Surveillance DynaMed's Systematic Literature Surveillance : Use of a reduced (4-dose) vaccine schedule for postexposure prophylaxis to prevent human rabies. MMWR Morb Mortal Wkly Rep . 2010;59(2):1.

Revision Information

This content is reviewed regularly and is updated when new and relevant evidence is made available. This information is neither intended nor implied to be a substitute for professional medical advice. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with questions regarding a medical condition.

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