Rabies

Dogly Infections

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Rabies

Signs and Symptoms

Rabies is a very serious infection of the nervous system that is caused by a virus. Rabies is usually transmitted by an animal bite, and humans who develop a rabies infection often have a history of being bitten by an animal in the 1 to 2 months before their rabies symptoms begin.

Highlights

People & Pets

Dogs & Chewing Habits

Rabies starts with a PRODROMAL PERIOD (premonitory symptoms indicating the beginning of a disease) that usually lasts for 1 to 4 days. Symptoms during this prodromal period include: fever, headache, malaise (a generally ill feeling); muscle aches; loss of appetite; nausea; vomiting; sore throat; cough; and fatigue. There may also be a tingling or twitching sensation around the area of the animal bite. This is the one most specific symptom of rabies at this stage of the rabies infection.

After the prodromal period, a second stage begins with symptoms that look like those of an encephalitis (inflammation of the brain). There may be fever as high as 105 degrees F (40.6 degrees C) with any of the following symptoms: irritability; excessive movements or agitation; confusion; hallucinations; aggressiveness; bizarre or abnormal thoughts; muscle spasms; abnormal postures; seizure (convulsions); weakness or paralysis (person cannot move some part of the body); extreme sensitivity to bright lights, sounds, or touch; increased production of saliva or tears. Also, there may be inability to speak as the vocal cords become paralyzed.

The last stages of rabies produce symptoms that reflect the infection's destruction of many important areas of the nervous system. There may be double vision, problems in moving facial muscles, abnormal movements of the diaphragm and muscles that control breathing, and difficulty swallowing. It is the difficulty in swallowing - combined with increased production of saliva - that leads to the "foaming at the mouth" usually associated with a rabies infection.

Finally, the person with a rabies infection can slip into a coma and stop breathing. Without life support measures, death usually follows within 4 to 20 days after symptoms of rabies begin.

Description

Rabies is an infection of the nervous system that is caused by the rabies virus. The rabies virus is carried in the saliva of infected animals and is usually transmitted to humans though an animal bite. In rarer cases, the virus may also spread to humans when an infected animal's saliva touches someone's mucous membranes (moist skin surfaces, like the mouth or inner eyelids) or contacts an area of broken skin - a cut, scratch, bruise, or open wound.

Not all animals are equally likely to carry the rabies virus. In the United States, the most common carriers of rabies are bats, raccoons, skunks, and foxes, with a few cases also reported in wolves, coyotes, bobcats, and ferrets. Animals that are not usually expected to carry rabies include small rodents (hamsters, squirrels, chipmunks, mice), rabbits, and hares.

Twenty-one of the 36 human rabies cases in the United States from 1980 to 1997 have been linked to bats. Most other countries cite dogs as the major source of rabies among humans.

Once the rabies virus enters the human body through an animal bite, it probably begins multiplying in the surrounding muscle. This is why part of the first doses of anti-rabies medicine (rabies immune globulin given to prevent infection after an animal bite) is usually injected right into the area around the animal bite. Eventually the rabies virus travels up a nearby nerve from the bite area to the brain. Once it reaches the brain, the rabies virus infects many important brain areas and finally causes death.

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