What is rabies?|
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
-- (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:
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
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?
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:
References and further information:|
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