Rabies

Rabies, also known as hydrophobia, is a life-threatening viral infection that affects the brain and central nervous system. Humans and all warm-blooded animals are vulnerable to rabies.


Causes/associated factors
Rabies is found throughout the United States, except Hawaii. The vast majority of infected animals are wild, most commonly raccoons, skunks, bats, foxes, coyotes, woodchucks and opossums. Domestic animals such as dogs, cats, cattle, horses, sheep, pigs and ferrets can also be affected. In the United States, rabies in humans is rare. Each year, however, up to 40,000 Americans receive shots to prevent rabies after exposure to a potential infection. Only one to two cases each year are fatal, most often because the affected person is unaware of the exposure to rabies and does not seek medical care.
Vaccinating domestic pets against rabies has significantly decreased the incidence of the disease in the United States, as well as the number of necessary preventive shots after exposure. Today, most cases of human rabies in the United States related to dog bites occur from bites while traveling abroad. Generally, the international traveler faces a greater risk of rabies -- particularly in developing countries.


Transmission
The rabies virus, found in the saliva of infected mammals, spreads most often to other animals or people through bites that break the skin. Licking mucus membranes or open wounds with infected saliva can also spread the virus. Airborne transmission has occurred in caves holding millions of bats as well as labs where the virus is present, although the method of transmission in these cases is not understood. Throughout the world, eight people have developed rabies after receiving corneal transplant tissue from people with undiagnosed rabies. (The cornea is the clear surface covering the eye.) These are the only documented cases of rabies being passed from one person to another. This risk has been reduced by stricter guidelines for donor corneas.
Sometimes, the source of exposure to rabies cannot be identified.

Because the rabies virus is inactivated by drying and ultraviolet light, saliva that has dried or been exposed to sunlight is not considered infectious. Also, petting a rabid animal or contacting its blood, urine or feces is not considered a rabies exposure.


Signs/symptoms
In humans
Once inside the body, the rabies virus multiplies and gains access to nearby nerves. It travels along these nerves to the spinal cord and finally to the brain. Symptoms begin when the virus reaches the brain. The time from the bite until the appearance of symptoms varies depending on the severity of the wound, the amount of virus transmitted, the nerve supply near the wound and its distance from the brain. For humans, most symptoms develop between four and 12 weeks after exposure (symptoms may develop as early as four days after exposure or years later). Once symptoms appear, rabies in humans is nearly always fatal within a few days to a week. (The few people who have survived rabies all received preventive rabies treatment either before or after their exposure.)

Early symptoms may include:

itching, numbness, pain or other sensation at the bite site (which may already be healed)
fever
headache
general feeling of illness
apprehension, anxiety or depression
loss of appetite, nausea or vomiting
Within a few days, the illness develops into either classic or paralytic rabies. The symptoms of classic rabies may include:

violent contractions of the diaphragm and respiratory muscles when drinking, looking at water or hearing running water, or when air is blown in the face
increased saliva production
confusion
intense anxiety
seizures
Paralytic rabies is characterized by:

muscle weakness, often beginning in the bitten extremity but spreading throughout the body
paralysis
Both forms of rabies may lead to coma with lung and heart failure.

In animals
As in humans, the rabies virus travels to an animalays. For infected dogs, cats and ferrets, the virus may be present in the saliva three to seven days before symptoms develop. For other animals, this time frame may be longer.

After biting another animal or a human, dogs, cats and ferrets are typically confined for 10 days and observed for symptoms of rabies. There have been no documented cases of rabies developing in these animals after the 10-day confinement period.

For animals, common signs of rabies include:

fever
agitation
confusion
seizures
excessive salivation or drooling
aggressive behavior
daylight sightings of a typically nocturnal animal
inability to walk or dragging of hind quarters
Rabies may also be fatal for animals. If you detect any signs of illness or changes in your pet's behavior, no matter how small, consult your veterinarian immediately. It is also important to contact your veterinarian immediately if your pet has been exposed to a potentially rabid animal, even if your pet has been vaccinated. Rarely, rabies has developed in animals with current vaccinations.


Diagnosis
For humans, diagnosis is based on the person's history of exposure and current symptoms. As many as one-third of cases have no known exposure. If rabies is suspected, the diagnosis can be confirmed by:
doing a skin biopsy (taking a tissue sample for further evaluation in a lab) from the nape of the neck or a tissue biopsy from the brain
testing the person's saliva, cerebrospinal fluid (the fluid protecting the brain and spinal cord) or eye fluid for evidence of the virus
testing the person's blood or cerebrospinal fluid for rabies antibodies

Treatment
If preventive treatment is given before the virus gains access to nearby nerves, illness may be avoided. Immediately after an animal bite of any type, thoroughly wash the wound with soap and water.
After washing the wound, seek medical care immediately. Your doctor will provide further care for your wound and evaluate your risk of rabies. If necessary, your local public health department will be consulted. Remember, however, even despite intensive care, rabies is nearly always fatal for humans once symptoms develop. Fortunately, two types of immunizations can help prevent rabies. The rabies immune globulin provides immediate immunity that lasts up to 21 days, and the rabies vaccine triggers an antibody response that takes up to 10 days to develop. Once you develop antibodies against rabies, you'll be protected for at least two years. If you haven't been immunized against rabies, both the immune globulin and the vaccine will be given as soon as possible. Youys after the first.

Here are some additional treatment guidelines for both you and the animal in question:

The Centers for Disease Control and Prevention recommends that you seek medical care for any animal bite, even if the animal has been immunized against rabies. If you're bitten by a dog, cat or ferret and the animal looks healthy, the animal should be confined for 10 days. If the animal shows any signs of rabies during this time or is suspected to be rabid, you'll need preventive treatment. (The animal's veterinarian should also be called.) If the animal's rabies status is unknown, the animal is not up-to-date with its immunizations, or it's acting strangely or appearing ill, contact public health officials immediately after the bite.

Many states require notification of bites from familiar dogs and cats, as well as strays. Check with your local public health officials.

If you're bitten or scratched by a wild animal such as a skunk, raccoon, woodchuck, coyote, opossum, fox, bat or most other meat-eating animals, you'll need preventive treatment immediately. Public health officials also need to be notified. If possible, have the animal euthanized and tested for rabies. If rabies is not detected, your doctor may give the OK to discontinue preventive treatment.

If you're bitten by livestock or a small rodent, rabbit, hare, beaver or other mammal, discuss the need for preventive treatment with your doctor or public health officials. (The bites of small rodents such as squirrels, hamsters, guinea pigs, gerbils, chipmunks, rats and mice, as well as rabbits and hares, rarely require preventive treatment, but it's best to contact the public health department anyway.)

If you've had close exposure to bats (such as awakening to find a bat in your room or finding a bat in your child's room) or any unfamiliar animals, a rabid animal, a pet that was exposed to or bitten by a rabid animal, or an animal known to carry rabies (such as raccoons, foxes or skunks), contact the public health department even if you weren't bitten or can't see any obvious signs of a bite.
Although immediate preventive treatment is best, it may still be effective later. If you question whether you may have been exposed to rabies, seek treatment regardless of how long it's been since the exposure. Remember, sometimes rabies can take years to develop in humans.


Pregnancy-specific information
Pre-exposure and postexposure preventive treatment is considered safe during pregnancy. Consult your doctor for details.

Senior-specific information
Growing older is not a risk factor for developing rabies.

Prevention
If you have a dog, cat or ferret, keep his or her rabies vaccinations current. Also help your pet avoid contact with wild animals. If another animal bites your pet, seek veterinary care. For yourself, consider the following suggestions:
Avoid contact with wild or unfamiliar animals. Do not touch them, even if they're dead.
Do not leave pet food, open garbage cans or litter outdoors as it may attract wild or stray animals.
To keep animals from entering your home, seal any basement, porch or attic openings. If you have a fireplace, cap the chimney.
Report any stray or wild animals acting strangely or appearing ill to the local animal control agency.
Teach children never to approach unknown animals or animals that appear hurt.
If you or your child are bitten by an animal, seek medical care immediately.
If you have a high-risk occupation (such as an animal control agent, lab worker, veterinarian or forest ranger), consider a pre-exposure rabies vaccination. People who explore caves for enjoyment should also be immunized, as should those traveling to areas where rabies is not controlled. For pre-exposure vaccination, three injections are given in the upper arm. The second injection is given seven days after the first, and the third is given 14 or 21 days after the second. Booster shots are needed if potential exposure to rabies is frequent.

If you have a possible rabies exposure after receiving the pre-exposure vaccination, you still need medical treatment. The vaccination will simplify your treatment and may provide some protection if treatment is delayed or you have an unnoticed exposure to rabies.

Adverse reactions to the vaccine are usually mild. The most frequent side effects include:

pain, redness and swelling at the injection site
headache
nausea
abdominal pain
muscle aches
dizziness
Although rare, a serious allergic reaction to the vaccine is possible. If you develop an allergic reaction to the vaccine, its ability to prevent a fatal disease may be jeopardized. In some cases, the vaccine may be given with medication to help prevent allergic reactions.