Rabies is a viral disease that causes inflammation of the brain in humans and other mammals. Rabies is a fatal but preventable viral disease. It can spread to people and pets if they are bitten or scratched by a rabid animal. Saliva from an infected animal can also transmit rabies if the saliva comes in contact with the eyes, mouth or nose. In the United States rabies is mostly found in wild animals like bats, raccoons, skunks and foxes. However, in many other countries dogs still carry rabies and most rabies deaths in people around the world are caused by dog bites.
Signs and Symptoms
The incubation period for rabies is typically 2–3 months but may vary from 1 week to 1 year, depending upon factors such as the location of virus entry and viral load. Initial symptoms of rabies include a fever with pain and unusual or unexplained tingling, pricking or burning sensation (paraesthesia) at the wound site. As the virus spreads to the central nervous system, progressive and fatal inflammation of the brain and spinal cord develops. The symptoms eventually progress to delirium and coma. Death usually occurs 2 to 10 days after first symptoms.
Rabies is referred to as hydrophobia (“fear of water”) throughout its history.It refers to a set of symptoms in the later stages of an infection in which the person has difficulty in swallowing, shows panic when presented with liquids to drink, and cannot quench their thirst. Any mammal infected with the virus may demonstrate hydrophobia. Since the infected individual cannot swallow saliva and water, the virus has a much higher chance of being transmitted, because it multiplies and accumulates in the salivary glands and is transmitted through biting.Hydrophobia is commonly associated with furious rabies, which affects 80% of rabies-infected people. The remaining 20% may experience a paralytic form of rabies that is marked by muscle weakness, loss of sensation and paralysis. This form of rabies does not usually cause fear of water.
In animals, rabies is diagnosed using the direct fluorescent antibody (DFA) test, which looks for the presence of rabies virus antigens in brain tissue. In humans, several tests are required. Human rabies can be confirmed intra-vitam and post mortem by various diagnostic techniques that detect whole viruses, viral antigens, or nucleic acids in infected tissues (brain, skin or saliva).
Post-exposure prophylaxis (PEP) is the immediate treatment of a bite victim after rabies exposure. This prevents virus entry into the central nervous system, which results in imminent death.
PEP consists of:
- Extensive washing and local treatment of the bite wound or scratch as soon as possible after a suspected exposure;
- A course of potent and effective rabies vaccine that meets WHO standards and
- The administration of rabies immunoglobulin (RIG), if indicated.
Starting the treatment soon after an exposure to rabies virus can effectively prevent the onset of symptoms and death.
Almost all human exposure to rabies was fatal until a vaccine was developed in 1885 by Louis Pasteur. The following can help reduce risk of contracting rabies:
- Vaccinating dogs, cats and ferrets against rabies
- Contacting an animal control officer upon observing a wild animal or a stray, especially if the animal is acting strangely
- If bitten by an animal, washing the wound with soap and water for 10 to 15 minutes and contacting a healthcare provider to determine if post-exposure prophylaxis is required.
Vaccination after exposure, PEP is highly successful in preventing rabies. In unvaccinated humans rabies is virtually always fatal after neurological symptoms have developed.