Rabies What is rabies?
Symptoms
Prevention
Treatment
References

In California during the summer of 2003, a 66-year-old man was bitten on the finger by a bat. Five weeks later, the man went to the emergency room. He complained of chest pain and said that over the past few weeks he had felt drowsy, weak and ill. The man's condition continued to get worse: he became confused, disoriented and developed a fever and breathing problems. A week after he entered the hospital, the man was dead. Tissue samples sent to the laboratory were found to contain the rabies virus carried by the silver-haired bat (Lasionycteris noctivagans).
-- (Source: MMRR Weekly, January 23, 2004, 53:33-35)
Human rabies is rare in the United States because people who are exposed to rabies can get shots to prevent the disease. Many people in countries without adequate control of rabies, however, are at risk for an infection. The World Health Organization (WHO) estimates that rabies kills 40,000 to 70,000 people each year and 10 million people are treated for exposure to rabies.

What is Rabies?

Rabies is a disease caused by a virus that attacks cells of the nervous system. A virus is a small germ. Viruses can cause diseases such as the flu, chicken pox, smallpox, measles and hepatitis. A virus can enter a cell of the body and multiply. The infected cell may die and the virus can move on to infect other cells. Once the rabies virus enters the body, it is picked up by peripheral nerves and transported to the central nervous system (brain and spinal cord). The virus moves toward the brain at a rate of between 12 to 100 mm/day. Within nerve cells, the virus multiplies and then spreads to other parts of the body, including the salivary glands.

Electron microscope photograph
of the rabies virus.
Rabies is spread through the saliva of an infected animal. People and other animals can get rabies if they are bitten or scratched by an infected animal. Bats and raccoons often carry rabies, but dogs, cats, skunks, foxes, wolves and coyotes can also be infected. The rabies virus belongs to the family of Rhabdoviruses. When seen with an electron microscope, the rabies virus has a bullet-shaped appearance.
Cases of Animal Rabies, 2004.

Cases of Animal Rabies, 2004

What are the Symptoms of Rabies?

Symptoms of rabies usually start within two to eight weeks after a person is bitten. However, in rare cases, it may take more than a year for symptoms to develop.

The first signs of rabies may look similar to the flu:

Fever -- Headache -- Nausea -- Depression -- Sore Throat -- Stiff Muscles -- Loss of Appetite

Pain, itching or tingling at the site of the bite may also be present.

These symptoms may be followed by more serious signs:

Anxiety -- Confusion -- Convulsions -- Hallucinations -- Insomnia
Paralysis -- Breathing Problems -- Coma

Hydrophobia (fear of water) is seen in 50-80% of people infected with rabies. The fear of water develops because people have trouble swallowing.

Some animals infected with rabies may become restless and aggressive. They might try to bite other animals or objects. Other infected animals may become shy and try to hide.

Once rabies attacks the central nervous system, it causes encephalitis (brain swelling). Inflammation surrounding brain blood vessels is often seen. Areas of the brain frequently targeted by the rabies virus are the hippocampus, limbic areas, medulla and cerebellum. If rabies goes untreated, it is almost always fatal and there is no cure.

How Can Rabies Be Prevented?

  1. Stay away from wild animals: if you go on hikes in the woods, do not pet or feed any animals you meet. Remember, bites and scratches can transmit rabies.
  2. Stay away from stray animals: you do not know if these animals have been vaccinated against rabies.
  3. Discourage pests that may carry rabies: cover your trash cans and don't leave pet food outside for wild animals to get.
  4. Make sure your pets are vaccinated against rabies: effective vaccines are available for dogs, cats, ferrets, horses, cattle and sheep. The number of cases of animal rabies in pets and domesticated animals has been reduced since the 1950s when vaccination of these types of animals started. Rabies in wild animals is still high.
  5. Get yourself vaccinated: if you will be working or traveling in an area where you may encounter rabid animals (e.g., a veterinary office, wilderness, virus laboratory), you might consider getting vaccinated.
  6. Call the animal control office: if you see an animal behaving strangely.

Some countries are attempting to vaccinate wild animals using an oral rabies vaccine. Food with the vaccine is dropped from planes into the wilderness. Animals who eat this food get a snack and are protected against rabies should they be exposed to the virus.

How is Rabies Treated?

If you are bitten by an animal:

  1. First aid: immediately wash the bite or scratch with soap and water.
  2. See a doctor: a series of injections given as soon as possible after a bite is usually effective in preventing rabies. The first injection near the site of the bite contains antibodies that fight the rabies virus before it can reach the central nervous system. This protection lasts only a few weeks. A series of five injections given over the next few weeks helps a person make his or her own antibodies against the rabies virus. This provides long-lasting protection against rabies.
  3. Have the animal quarantined (if possible): the animal will be watched for 7-10 days to see if it develops signs of rabies.

Did you know?

  • Rabies has been found in every state of the US except for Hawaii.
  • Only mammals can get rabies. Birds, fish, snakes and frogs do not get rabies.
  • Rabies is NOT transmitted through contact with blood.
  • The word "rabies" comes from the Latin word meaning "to rage."
  • The word "hydrophobia" comes from the Greek words meaning "water" and "fear."
  • Louis Pasteur and his research team developed the first successful rabies vaccine. This vaccine was tested on Joseph Meister on July 6, 1885. Joseph was a 9-year-old boy who was bitten 14 times by a rabid dog. Dr. Pasteur gave Joseph a shot that prevented rabies.
  • In the United States in 2004, there were 6,836 cases of rabies in nonhuman animals and 8 cases in human beings reported to the to the CDC. Rabies was found most often in raccoons (2,564 cases), skunks (1,856 cases) and bats (1,361 cases). (Reference: Krebs, J.W., Mandel, E.J., Swerdlow, D.L. and Rupprecht, C.E., JAVMA, 227:1912-1925, 2005)
  • Eight people have died after receiving corneal transplants from people infected with the rabies virus. The risk of such human-to-human infections is very low because of improved screening of organ donations.
  • A bat bite often goes undetected because bat teeth can be small and the wound may not be large.
  • Neuroscientists use the rabies virus in an experimental method to trace neuronal pathways in the brain.
  • Approximately $300 million is spent each year in the United States to prevent rabies. Most of this money is spent on vaccinating dogs.
  • Rabies is discussed in the book Old Yeller by Fred Gipson. The dog, Old Yeller, protects a family from a rabid wolf. Unfortunately, Old Yeller is bitten by the wolf. The family decides it is better to kill Old Yeller rather than take the chance that the dog will develop rabies.

References and further information:

  1. Compendium of Animal Rabies Prevention and Control, 2007 - from the CDC
  2. Rabies Infection and Animals - from the CDC
  3. Rabies Page for Kids - from the CDC
  4. Rabies Control and Prevention, 2005 - from the CDC
  5. Rabies - from the CDC
  6. Rabies Fact Sheet - from the National Institute of Allergy and Infectious Diseases
  7. Kaplan, C., Turner, G.S. and Warrell, D.A., Rabies: the facts, New York: Oxford University Press, 1986.
  8. Woldehiwet, Z., Rabies: recent developments, Research in Veterinary Science, 73:17-25, 2002.
  9. Jackson, A.C., Update on rabies, Current Opinion in Neurology, 15:327-331, 2002.

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