What Is Rabies?
Rabies is an acute and deadly viral infection of the central nervous system. It is one of the most terrifying diseases known to man. Although rabies in humans is rare in the United States, as many as 18,000 Americans get rabies shots each year because they have been in contact with animals that may be rabid (rabies-infected). In 1998 according to the U.S. Centers for Disease Control and Prevention (CDC), only one person died of rabies in this country.
In other parts of the world, however, many people die of rabies each year. The World Health Organization (WHO) estimates that around the world more than 40,000 people die every year from rabies. WHO also estimates that 10 million people worldwide are treated after being exposed to animals that may have rabies.
Rabies is caused by a virus that is in the saliva of infected animals, and it is usually transmitted by bites from infected animals. All warm-blooded animals can get rabies, and some may serve as natural reservoirs of the virus.
Rabies is found in all of the United States, except Hawaii, and in many other countries around the world, including Canada and Mexico. The disease may be absent from large areas for many years, and then reappear suddenly or gradually by invasion from bordering countries or by the introduction of an infected animal.
What Animals Usually Get Infected With Rabies?
Rabies can affect wildlife such as raccoons, skunks, and bats, as well as household pets such as dogs and cats. Vaccination of pets and livestock is the most effective control measure to prevent the disease in these animals and subsequent human exposure. In fact, in the United States, such programs have largely eliminated canine (dog) rabies. In 1998, wild animals accounted for 93 percent of the 7,962 reported animal rabies cases in the United States and Puerto Rico. Rabies in raccoons accounted for 44 percent of cases, skunk rabies for 28.5 percent, bat rabies for 12.5 percent, and fox rabies for 5.5 percent of the cases. Only rarely, rabies is found in rabbits, squirrels, rats, and opossums.
Health officials are particularly concerned about rabies in raccoons because raccoons are often in close contact with household pets, especially dogs and cats. Increasingly, bats are being shown to be important transmitters of rabies to humans.
How Can An Animal With Rabies Infect A Person?
Most people get rabies from being bitten by a rabid animal. Rarely, if a person has broken skin, like a scratch, which comes in contact with animal saliva full of rabies virus, that person may get infected. But rabies also can be spread in the air, as has occurred in caves where infected bats live.
What Should I Do If I Think I've Been In Contact With Rabies?
If you have been bitten or scratched by any animal, you should:
* Clean the wound immediately with soap and water to remove saliva from the area,
* Call a doctor right away, and
* Notify the state or local health department.
If soap is not available, for example, when hiking, you can use water alone. But be sure to wash with soap and water as soon as possible. Allow the wound to bleed, which also will help to clean it.
There are situations in which it is possible that a person has had close contact with a bat and not known it, as when a sleeping person awakens to find a bat in the room. Therefore, CDC now recommends that people seek medical help even if they can't see a bat bite or scratch, or may have had mucous membrane exposure. (Mucous membranes include the linings of the eyes, mouth, and nose.)
The possibility of getting rabies from rodents, including squirrels, is small. If you have been bitten by one, however, you should still consult a doctor right away.
In fact, you should avoid contact with any wild animal.
How Do Doctors Diagnose Rabies?
If you think you may have been exposed to rabies, the doctor or other health care worker will ask you questions about when you possibly were in contact with an infected animal and if you have any symptoms. Laboratory tests to make sure that the diagnosis is correct involve looking for the rabies virus in your saliva or brain tissue. Unfortunately, this is usually not possible until late in the disease. The doctor must use sophisticated laboratory tests to show rabies or evidence of rabies virus.
What Are The Symptoms Of Rabies?
When symptoms do appear, it is usually 30 to 50 days following exposure. There is a direct relationship between how severe the bite is and where on the body the person bitten and how long it takes for symptoms to appear. For example, if a person's head is severely bitten, symptoms may show up in as few as 14 days. Under rare conditions, a person may not have symptoms for a year or longer after exposure to the virus.
The doctor will suspect rabies if someone has symptoms such as:
* A short period of mental depression,
* Restlessness,
* Abnormal sensations such as itching around the site of the bite,
* Headache,
* Fever,
* Tiredness,
* Nausea,
* Sore throat, or
* Loss of appetite.
Other early symptoms include:
* Stiff muscles,
* Dilation (enlargement) of pupils of the eye,
* Increased production of saliva, and
* Unusual sensitivity to sound, light, and changes of temperature.
How Is Rabies Treated?
If a doctor decides that you probably have been exposed to rabies, post-exposure (after a being bitten) rabies shots should begin at once, preferably within 24 to 48 hours of exposure. In fact, many experts recommend that treatment should be started even if the delay is much longer than that.
The first treatment, sometimes called passive immunization, provides immediate but temporary protection by injecting antibodies (disease-fighting proteins or immunoglobulins) into the patient. Currently, CDC recommends treating a patient immediately with one dose of human rabies immunoglobulin (HRIG) shots.
After the first treatment, CDC recommends that patients be given a rabies shot, which starts the body producing its own antibodies. It takes some time for the body to produce the antibodies, but these antibodies provide longer-lasting protection. Because rabies has an unusually long incubation period, however, the body has time to respond to the vaccine and produce protective antibodies.
There are now three types of rabies vaccines, all of which are made from killed rabies virus:
* Human diploid cell vaccine (HDCV),
* Rabies vaccine adsorbed (RVA), and
* Purified chick embryo cell culture (PCEC).
What Is Rabies Like In Animals?
Early signs of rabies in animals include a change in behavior, fever, loss of appetite, and often, a change in phonation, such as a change in tone of a dog's bark. These signs are often slight, however, and people may not notice them. A few days after infection, the animal may be very restlessness and become very agitated and tremble. An affected dog may growl and bark constantly, and will viciously attack any moving object, person, or animal it comes across. This excited state usually lasts three to seven days, and is followed by convulsions and paralysis.
In some instances, signs of excitement and irritability are slight or absent, and paralysis develops within a few days of disease onset. In cases of this type, an early sign is often paralysis of the lower jaw, accompanied by increased drooling and foaming of saliva. The animal may appear to be choking on a foreign object. This is a dangerous trap for humans, who, in trying to help the animal, may expose themselves to infection without knowing it.
What Research Is Going On?
Scientists supported by the National Institute of Allergy and Infectious Diseases (NIAID) are focussing their rabies research on basic research and vaccine development. These scientists showed that the current human diploid cell vaccine provides protection against all strains of rabies isolated from around the world. Scientists are trying to develop a lower-cost vaccine because it is too expensive for many countries to use it widely. One new vaccine approach supported by NIAID is attempting to develop a modern, DNA-based vaccine that would show broad protection against rabies and be less costly.
*Material on this web page courtesy of the NIH
Images on this web page courtesy of USDA
Thumbnail link image of racoon courtesy of NPS
URL: http://www.niaid.nih.gov/factsheets/rabies.htm
