Rabies is a viral disease of mammals affecting the brain and the nervous system. It is transmitted to humans by the bite of a rabid animal. From the site of the bite, the virus travels via nerves to the brain. Then it spreads to other organs including, salivary gland and is shed in saliva. Most commonly, it causes encephalitis (inflammation of  brain) that progresses to coma and/or paralysis. An established rabies infection is almost always fatal, only few survivors have been documented to date. Rabies can be prevented before symptoms develop.

Cause

Rabies virus is the causative organism in this disease. It is transmitted to humans by the bite of a rabid animal, which includes dogs, cats in urban areas, bats, foxes, skunks, raccoons and coyotes  in the wild. It can potentially be transmitted by licks or scratches, as well. In rare cases, rabies can be transmitted through organ transplantation from infected donors.

Risk factors

People at high risk of rabies exposure are:

• Laboratory staff;
• Veterinarians;
• Animal handlers, zoo staff;
• Wildlife staff; or
• People in highly endemic areas.

Symptoms

Rabies shows symptoms in about 1-3 months after exposure, but may range from days to years. The development of symptoms takes time depending on the body part bitten by the rabid animal. A bite on the head, face or neck takes relatively shorter time to show symptoms and can cause death than a bite on other areas of the body, such as legs.

All non-immunized people bitten by rabid animals develop the disease unless proper prophylaxis is done. Usually, prodromal phase is seen first, followed by acute neurological phase and lastly coma and death ensues. Fever, body ache, headache, nausea, vomiting, tingling sensations around wound, pain are the main features of prodromal phase which lasts about a week. This is followed by the patient exhibiting excitement, terror, change in voice, seizures, hydrophobia and respiratory difficulty. Some patients also present with paralysis.  Later, this may progress to death due to respiratory paralysis or coma. 

When to seek care

Because of the inevitably lethal character of rabies infection, all exposed cases are taken as high priority and given aggressive post-exposure treatment. One should seek immediate medical care and prophylaxis:

• After wild animal bite;
• After sick or unidentified animal (dog) bite;
• If during observation period of 10 days, the culprit animal (domestic dog or cat which caused the bite) is lost or dies; or
• After exposure to bat (even without bite).

Diagnosis

It is important to suspect rabies and start post-exposure prophylaxis as there is no treatment once the symptoms occur. When symptoms suggestive of rabies occur, diagnostic tests are performed on saliva, blood, spinal fluid and skin biopsy.

Treatment options

Treatment of established rabies infection is mainly supportive. Chances of survival are very rare in established cases. Main treatment methods are:

• Admission in hospital;
• Alternative feeding because of spasm and hydrophobia;
• Treatment of convulsions; and
• Supported breathing and blood circulation.

Development of infection can be prevented after exposure (animal bite) by following post exposure methods.

Post exposure prophylaxis:

Rabies prophylaxis after exposure can be done by local wound treatment and vaccine therapy with or without rabies immunoglobulin.

• Local wound treatment: Immediate wound care of bites and scratches from suspected animal is undertaken. Thorough cleaning with soap and water is recommended.  Alcohol or iodine solutions can also be used for cleaning the wound.
• Vaccine therapy: Rabies vaccine, with or without rabies immunoglobulin should be given as soon as possible after exposure to rabies is suspected. Vaccine should be given even during pregnancy or to infants.

Antibiotics or tetanus toxoid are given depending on the wound and contamination state.

Pre-exposure prophylaxis:

People at high risk of exposure or in highly endemic areas are given pre-exposure rabies vaccination. Three intramuscular doses of rabies vaccine are given on the arm on days 0, 7 and 28.