What is Rabies? Causes and Transmission of Rabies

Rabies is a fatal infection caused by a virus affecting the brain and nervous system. It affects almost all animals and human beings. Human beings get the infection usually through the saliva of the affected animal.

In developing countries the infection is usually through the bite of a dog since the dogs are not systematically vaccinated. In the United States the Rabies spreads by bats.

The disease has been eradicated by means of regular vaccination and eradication programmes and hence the incidence of rabies in United States of America is rare. However in developing countries it is still existing and spread of the disease is usually due to a dog bite. Rabies is having zoonotic importance since it spreads from animals to human beings.

Therefore it is necessary to understand about the disease in animals and human beings to control or to take necessary preventive measures.

Rabies in Dogs:

Dogs are infected through the bite of an infected animal usually by another dog infected with rabies. But they can also get infection from other animals like cats, raccoons, foxes and bats. The virus is transmitted through the saliva. After the virus is deposited in the body of the dog it traverses through the nerve courses and finally reach the brain where it produce inflammation of the brain cells and consequent symptoms. Therefore reaching of the brain depends on the site of bite. If the bite is nearer to the brain the symptoms of rabies appear quickly. However it takes 3-8 weeks to reach the brain and the symptoms to appear. The incubation period is long sometimes takes even 6 months to one year.

Symptoms of Rabies in Dogs:

After the virus reaches the brain it produces the typical symptoms of rabies. The symptoms can be divided into three stages.

The first stage or the prodromal stage:

The animal refuses to take food, goes to solitary places and hides. Domesticated animal behave rather aggressively and refuse to obey the owners instructions. The animal gets slight fever looks anxious and irritable. The animal licks the site of the bite. Aggressive animals may become docile and mild. The prodromal stage lasts for 2-3 days and it passes into the next stage.

The second stage or furious stage:

The furious stage lasts for about 2-7 days developing aggressive symptoms. The eyes become red with a furious look and the dog tries to run away without any aim. This is particularly seen in street dogs. Salivation, lachrymation are seen. They try to bite unprovokingly animals and human beings coming on their way. They even bite the owners and recognition is lost. Gradually paralysis of hind limbs takes place and the animal enters the third stage.

The third or the paralytic stage:

During this stage the paralysis progresses and animal cannot swallow any liquids and the voice of the dog becomes hoarse with profuse salivation from the mouth. Some times the paralytic stage comes after the prodromal stage. Ultimately it becomes extremely weak and succumbs to the disease. Once the symptoms are seen the animal usually dies within 10 days due to respiratory failure.

Diagnosis of the Rabies disease:

Symptoms are itself suggestive of the disease. However diagnosis should be done by histo pathological studies of the brain. Therefore after the death of the dog the brain is dissected and the hypothalamus is sent to the diagnostic laboratory for histo pathological study and confirmation of the disease. Extreme care should be taken while collecting the brain sample and the carcass should be disposed of by incineration. The other test direct fluorescent antibody test on the brain tissue to detect the antibodies which is a most rapid and reliable test but the animal has to be euthanized for the test. Serum, spinal fluid and saliva can also be tested but the results are not 100% reliable.

Treatment:

Treatment is not useful and the affected animal will die therefore prevention is the only best method.

Prevention of Rabies in Dogs:

Dogs can be vaccinated against this disease. Regular vaccination protects the pets form this disease. Unprotected animal if they are bitten can be vaccinated with suitable vaccine to prevent the spread of the disease which is 100% useful and safe for the pets and the owners.

Preventive Vaccination:

Rabies vaccination is compulsory in many countries nowadays to prevent the spread. Vaccinated animal will be immune for infection and it is the sure way to protect. The first dose of vaccination can be given at the age of 3-4 months. The second dose can be given after 7 days. From then onwards the dog can be vaccinated every year. Most of the manufacturers give necessary instructions which can be followed. Regular vaccination of dogs with rabies vaccine protects the pets from the bites of rabid animals.

Post exposure treatment:

Generally public health officials recommend that unvaccinated pets if exposed to rabid dog bite should be euthanized as a safety procedure. If the pet owner is unwilling to euthanize vaccination can be done but the pet should be kept under observation for 6 months. In protected pets re-vaccination can be done and kept in observation for 45 days. Since rabies is a fatal disease and spreads from rabid animals to humans it has a zoonotic importance to protect the human beings. In most of the countries where the dogs are not systematically vaccinated against rabies humans get rabies through the bites of rabid dogs. Bats can also transmit the disease and it is a common feature in United States of America.

Symptoms of rabies in humans:

Infected persons by rabid animal if untreated get the disease within 15 days – 6 months depending on the site of the bite. If it is nearer to brain the onset of symptoms are faster and takes long time if the bite is farthest to the brain like the foot. The virus traverses through the nerves and reach the brain. When once it reaches it produce encephalitis with concomitant symptoms.

• Rabies in humans starts with flu like symptoms fever, chills and general malaise, restlessness, depression and severe exhaustion.
• The above symptoms last for about 2-7 days and followed by Paralysis of face and throat muscles.
• Severe thirst and the individual cannot swallow because of the paralysis of throat muscles causing inability to drink fluids even though thirsty. Restlessness increase and due to painful spasms of the throat muscles drinking of fluids become impossible. As soon as the person sees the water excitement and spasms start. For this reason rabies in human beings is also called hydrophobia.
• Voice become hoarse.
• Loss of consciousness progressing with paralysis of limbs leading to coma and death.

Once the symptoms are seen death is inevitable. Therefore being a fatal disease prevention and post exposure treatment is very essential in human beings. Veterinarians and people deal in laboratories with rabies virus for production of vaccines are at high risk. They should be vaccinated and their immunity levels should be checked periodically.

What precautions to be taken if any body gets exposed to Rabies?

• If a person is bitten with a rabid animal wash all the bites with soap and water.
• Rush for medical aid immediately.
• Treatment of the person should always be started as early as possible. Otherwise the dose of vaccination and the course of injections get modified.
• If the bitten animal either dog or cat is available it should be observed for about 10 days. If the animal survives up to 10 days after the bite without any symptoms of rabies treatment of the individual can be stopped. If the animal bitten is not available for observation treatment should be taken suspecting it as a rabid animal bite. Any chance should not be taken.

Prevention of Rabies:

• Vaccinate all pets regularly with anti rabies vaccination with a potential vaccine.
• Stray dogs should be removed by any means.
• People who are at high risk should be vaccinated against rabies.
• Persons exposed to rabies should be given prompt treatment and post exposure vaccination.

  Diseases and Disorders, Viral Diseases