Rabies Prevention, Symptoms and Diagnosis

The rabies virus infects the central nervous system, ultimately causing disease in the brain and death. The early symptoms of rabies in people are similar to that of many other illnesses, including fever, headache, and general weakness or discomfort.

As the disease progresses, more specific symptoms appear and may include insomnia, anxiety, confusion, slight or partial paralysis, excitation, hallucinations, agitation, hypersalivation (increase in saliva), difficulty swallowing, and hydrophobia (fear of water). Death usually occurs within days of the onset of these symptoms. Rabies is a preventable viral disease of mammals most often transmitted through the bite of a rabid animal.

Prevention
You can reduce the chances that your family is exposed to rabies. Vaccinate your pets dogs, cats, and ferrets can be infected by rabies. Report any stray animals to your local health authorities or animal-control officer. Remind kids that animals can be “strangers,” too. they should never touch or feed stray cats or dogs wandering in the neighborhood or elsewhere.

Symptoms and Signs
The first symptoms of rabies may be very similar to those of the flu including general weakness or discomfort, fever, or headache. these symptoms may last for days.

As the infection progresses, someone infected with rabies may develop any of these symptoms:

• irritability
• excessive movements or agitation
• confusion
• hallucinations
• aggressiveness
• bizarre or abnormal thoughts
• muscle spasms
• abnormal postures
• seizures (convulsions)
• weakness or paralysis (when a person cannot move some part of the body)
• extreme sensitivity to bright lights, sounds, or touch
• increased production of saliva or tears
• difficulty speaking

In the advanced stage of the infection, as it spreads to other parts of the nervous system, these symptoms may develop:

• double vision
• problems moving facial muscles
• abnormal movements of the diaphragm and muscles that control breathing
• difficulty swallowing and increased production of saliva, causing the “foaming at the mouth” usually associated with a rabies infection

Rabies Diagnosis
Though the behavioral symptoms of rabies are classic, a diagnosis based solely on the symptoms can be difficult because they are similar to other diseases, conditions, and complications. The inability to swallow, for example, could be caused by an object lodged in the throat. many factors can trigger aggressive, strange behavior and many animals are easily provoked when injured.

The only way to be 100% sure that an animal is rabid is to perform a direct fluorescent antibody test (dFA) on the brain tissue, which requires that the animal be euthanized. This is the most rapid and reliable test for rabies and it has been used for more than 40 years.

The dFA test is based on the principle that infected animals have rabies virus antigen (a protein) in brain tissue that reacts to antirabies antibodies (proteins produced by the immune system to fight disease and infection). The test involves inserting fluorescently labeled antirabies antibody molecules into the brain tissue, which bind to the rabies virus antigens and give off a bright glow when viewed through a special fluorescent microscope. A dFA test can also detect the presence of rabies antigens in the skin.

Tests that do not require euthanasia can be used to examine serum, spinal fluid, and saliva, but none of them can rule out rabies with 100% certainty. these tests are used only in humans and animals that cannot be euthanized.