Rabies

An acute viral disease of the central nervous system that is usually transmitted to humans by a bite from an infected warm-blooded animal. Untreated, the disease is a swift, deadly killer, and there is no cure; the only hope lies in giving a vaccine immediately after a bite from a rabid animal.

Although most people tend to associate rabies with dogs, in fact rabies today is more likely to be found in cats. Together with dogs and cattle, these animals make up nearly 90 percent of rabies cases in domestic animals, with horses, mules, sheep, goats, swine, and ferrets making up the rest. However, most cases of human rabies in the United States are caused by bats. Human cases have averaged just three cases a year since 1990; a total of 26 (74 percent) of the 35 human rabies deaths in the United States have been associated with batvariant rabies viruses. Other wild animals that carry the disease include skunks and raccoons, foxes, mongooses, groundhogs, and some rodents. Rabies has been on the rise in the northeastern United States, increasing dramatically between 1990 and 1993.

Cause
Rabies is actually a form of viral ENCEPHALITIS transmitted through infected animal saliva. The virus is concentrated in the salivary glands, which is why the disease is usually spread by a bite. The virus also invades and damages muscles involved in drinking and swallowing, causing excruciating pain when swallowing liquids. Although suffering from thirst, animal and human rabies victims can be terrified by the sight of water; hence, the other name for the disease—hydrophobia.

Rabies also can be transmitted when infected saliva comes in contact with a cut or skin break. Infected bat droppings also may transmit the disease, as can transplants from patients with undiagnosed rabies.

Symptoms
The incubation period in humans may range from 10 days to more than a year, although 30 to 50 days is average. (Animals usually develop symptoms between 20 and 60 days.) The length of the incubation period seems to depend both on the location of the wound (the farther from the brain, the longer the incubation) and the dose of the virus received. Without treatment, severe bites on the head or upper body could lead to symptoms sooner than a mild scratch on the ankle.

There are two forms of the disease. “Furious” rabies primarily affects the brain and causes an infected animal to be aggressive, highly sensitive to touch, and vicious—the “mad dog” image. “Paralytic” (or “dumb”) rabies primarily affects the spinal cord, weakening the animal so that it cannot raise its head or make sounds because its throat muscles are paralyzed. In the beginning stage of paralytic rabies, an animal may seem to be choking. In both forms, death may occur a few days after symptoms appear.

Symptoms in humans are mild at first and worsen over time, starting with an itching or burning at the bite site, followed by malaise, fever, headache, fatigue, and appetite loss. The child begins to grow restless, excitable, anxious, and irritable, with insomnia or depression. The child may begin to hallucinate, salivate, and have periods of intense excitement and painful muscle spasms of the throat induced by swallowing. As time goes on, other signs of nervous system damage, including disorientation or coma, follow. Four or five days later, the patient either may slip into a months-long coma ending in death, or die suddenly from respiratory or cardiac arrest.

Diagnosis
There are no tests that can detect rabies in humans at the time of a bite, and by the time symptoms appear, it is too late for treatment. The transmission of rabies by a bite can be hard to detect.

Treatment
If a child is bitten by a suspected rabid animal, the wound should be immediately washed with soap and water; the bite should be allowed to bleed to help wash out the wound. Medical help is needed at once. (If possible the animal should be trapped and confined.)

Rabies prevention no longer means a series of painful injections in the abdomen. If a child’s doctor decides to begin the antirabies immunization, it will involve a monthlong series of five intramuscular injections together with human rabies immune globulin that should be started on the day of the bite. Part of rabies human immunoglobulin is usually injected near the bite area.

Unlike other vaccines, the rabies immunization is administered after exposure to the virus. This unusual technique works because the rabies virus takes a long time to induce disease. Injections of rabies vaccine may prevent the disease from developing in a person bitten by an infected animal. There are currently two vaccines licensed in the United States, both of which work the same way— triggering the immune system to produce antibodies that neutralize the virus before it causes disease. The modern vaccines are highly effective and produce few side effects. It is the only way to treat the disease in humans.

Prevention
A pre-exposure vaccine series is available that is designed for people at high risk for exposure, such as veterinarians, cave explorers, animal handlers, and those who travel to countries where rabies is common. The series is given in three shots.