What is rabies?
Rabies is a viral disease where the infecting rabies virus is transmitted to humans through bite of infected dogs. However, in the United States, the infection may spread by other animals like coyotes, raccoons, bat and skunks. The disease is almost always fatal after the appearance of symptoms.
Therefore pre-exposure vaccination to people who are at increased risk of being infected with the virus and post exposure vaccination immediately after contact with a possible source of infection is very important. Worldwide rabies leads to 55,000 deaths per year and about 97% of human rabies occurs due to infected dog bite.
Symptoms of Rabies
Symptoms of rabies usually occur at advanced stage of the disease and in almost all the cases leads to death of the infected person. These symptoms are :
High fever along with agitation and increased irritability, intense headache, anxiety, confusion and disorientation. Often this period of hyper excitability is followed by period of calmness and lucid intervals. The period of hyper excitability usually lasts for less than 5 minutes and usually precipitated following exposure to bright light, touch and sound or sometimes the attack may occur spontaneously. In about 20% of the patients of rabies this hyper excitable phase may not occur, patient becomes quiet with paralysis of limbs, high fever and severe headache.
Difficulty in swallowing and excessive saliva production.
Characteristically the patient fears water due to painful swallowing (hydrophobia).
Hallucination, sleeplessness and partial or complete weakness or paralysis of limbs.
Finally the patient becomes comatose and death usually occurs due to stoppage of heart and lung function (cardiopulmonary arrest).
Causes of Rabies
Rabies is a zoonotic disease where the infecting virus spreads from infected animals to humans. Usually bite from an infected animal is the most common route of transmission of infection, however rarely direct contact with saliva and open wound may lead to infection. Till now there is no documented case of spread of infection from infected rabies patients however rarely transplantation of infected organ may cause rabies.
Rabies virus affects the nervous system of the human body. The virus after entry into the body through saliva is carried to the brain tissue by traveling through peripheral nerves at a speed of 12-24mm/day and multiplies in the nerve ganglia. The time interval between contracting the infection and appearance of first symptoms (incubation period) may vary from days to years, but in humans is about months.
The incubation period depends upon the distance the rabies virus has to travel from the site of entry to the brain. The first symptom signifying infection is pain and sensation of numbness at the site of entry. From the brain the virus spreads to the peripheral regions and the salivary glands.
Risk factors
Common risk factors include travelling or living in developing countries where prevalence of rabies is high, activities that increase the risk of contact with wild animals, veterinary doctors, working in laboratory with rabies virus.
Rabies Treatment
There is no treatment available once symptoms of rabies have occurred. Treatment of patients bitten by dogs or other possible carrier animals of rabies include local cleaning of the wound with soap and water, administration of human rabies immunoglobulin locally and rabies vaccine immediately, after 3, 7 and 14 days. People who are at increased risk of coming in contact with rabies infected animals should receive pre exposure rabies vaccination.