Brain & Nerve
Diseases & Conditions
Contributed byKrish Tangella MD, MBAJul 27, 2023

What are the other Names for this Condition? (Also known as/Synonyms)

  • Canine Rabies
  • Hydrophobia Lyssa
  • Rabies Virus Infection

What is Rabies? (Definition/Background Information)

  • Rabies is a preventable, but deadly viral disease, caused by a virus that attacks the nervous system. It is usually transmitted by infected saliva that penetrates the skin through a bite from an infected animal
  • Stray dogs in developing countries, such as Africa and Southeast Asia, have the highest incidence of infecting individuals with the Rabies virus
  • The signs and symptoms that may occur following the bite or injury by the animal can include pain at the wound site, fever and chills, sore throat, and general feeling of illness
  • An immediate treatment following the infected animal bite with human rabies immunoglobulin therapy and following the strict schedule of injections can help in a cure
  • Once an individual starts to show signs and symptoms of the Rabies virus, this infection is usually fatal

Who gets Rabies? (Age and Sex Distribution)

  • Rabies may occur in individuals of all ages, races, ethnic groups, or gender who are bitten by an infected animal
  • 40% of individuals who are bitten by infected animals are children younger than 15 years old

What are the Risk Factors for Rabies? (Predisposing Factors)

Common risk factors associated with Rabies include:

  • Coming into close contact with animals that can transmit the Rabies virus, such as dogs, cats, foxes, wolves, bats, and many more, which are not vaccinated against the virus
  • Individuals, predominantly children, who live in (or travel to) the endemic regions, such as to Africa or Southeast Asia, have an increased risk
  • Working in laboratories with the Rabies virus
  • Individuals who live in remote and rural areas that increases the chances of contact with infected animals (wild animals)
  • Wounds close to the brain, such as in the neck or head region, caused by rabid animals, results in faster infection of the brain; this is because the virus has lesser distance to travel
  • Certain activities that put individuals at risk of coming into contact with an infected animal, such as camping outdoors or exploring caves

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases ones chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Rabies? (Etiology)

Rabies is a deadly viral disease caused by the Rabies virus that attacks the central nervous system including the brain. The transmission of Rabies virus may occur in the following manner:

  • Individuals who are bitten by an infected animal; infected dogs are the most common cause of Rabies deaths worldwide
  • The transmission may occur through the saliva on open wounds (through infected animal licks)
  • Inhalation of the virus
  • Transplantation of an infected organ

What are the Signs and Symptoms of Rabies?

Rabies incubation period is usually between 1-3 months following entry of the virus into the body. But, this may also range from a few days to several years.  The initial signs and symptoms of Rabies may include:

  • Elevated fever and chills, excess sweating
  • Restlessness (agitation), difficulty in sleeping
  • Fatigue (extreme tiredness)
  • Pain at the site of the bite
  • Sore throat
  • Headache
  • Reduced appetite
  • Nausea and vomiting
  • General feeling of discomfort or uneasiness (malaise)

Symptoms following onset of Rabies may include:

  • Persistent anxiety
  • Hydrophobia (fear of water)
  • Loss of muscle function; difficulty swallowing/speaking
  • Excessive salivation
  • Confusion, hallucinations
  • Seizures
  • Partial paralysis
  • Dysphasia

How is Rabies Diagnosed?

Currently, there are no available methods a physician may use to determine if a rabid animal has transmitted the Rabies virus after an attack or bite. Common tests physicians use to diagnose Rabies in individuals who exhibit signs and symptoms include:

  • Immunofluorescence test is used to look at the brain tissue after the animal is dead. This is performed to discover if the animal had had Rabies
  • Immunofluorescence test is also performed in humans by using a piece of skin from the neck
  • A spinal tap test may be performed to check for the Rabies virus within the spinal fluid
  • Analysis of saliva and spinal fluid to detect Rabies virus
  • Blood and tissue tests may be used to diagnose Rabies in individuals who show signs and symptoms of the Rabies infection

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Rabies?

The possible complications associated with Rabies include:

  • Urinary retention or the decreased ability to urinate
  • Encephalitis or infection of the brain
  • Increased intracranial pressure (ICP)
  • Hypotension (low blood pressure)
  • Cardiac dysrhythmia or irregular heartbeat
  • Myocarditis, which is inflammation of the heart muscles
  • Hypernatremia: Electrolyte disturbance in which the sodium concentration in the serum is lower than normal
  • Cerebral edema: Excess accumulation of water in the intracellular and extracellular spaces in the brain
  • Ileus: Disruption of the normal ability of the gastrointestinal tract
  • Respiratory failure
  • Poikilothermia: Inability to maintain a constant core temperature
  • Diabetes insipidus: A condition characterized by excessive thirst and excretion of diluted urine
  • In rare cases, individuals may develop an allergic reaction to the Rabies vaccine
  • Respiratory acidosis
  • Acute renal failure (a rapid loss of kidney function)
  • Congestive heart failure or the inability to provide adequate blood supply to the heart
  • Gastrointestinal hemorrhage: Excessive bleeding that begins within the gastrointestinal tract
  • Paralysis and coma

Following onset of Rabies signs and symptoms, death due to Rabies infection is almost inevitable. So far, only 2 individuals with confirmed Rabies have recovered after receiving intensive and extensive treatment.

How is Rabies Treated?

The treatment of Rabies following may include:

  • Firstly, the wound is cleaned with soap and water
  • The physician will then check if the individual’s tetanus and immunization schedule are to current status

Post-exposure prophylaxis:

  • A dose of human rabies immunoglobulin treatment (HRIG) against Rabies virus at the wound site provides immediate protection against the virus
  • Strict schedule of injection of the Rabies vaccine (administered in the arm) can help an individual’s immune system produce antibodies against the virus
  • Preventive vaccine should be administered in 5 doses over 28 days
  • Immunization and treatment should continue up to 4 days following exposure or a bite
  • The human diploid cell vaccine (HDCV) and purified chick embryo cell culture vaccine (PCECV) has been used in the US to effectively protect against Rabies

Currently, there is no effective treatment for Rabies once an individual begins to show signs and symptoms of the viral infection.

How can Rabies be Prevented?

Preventive measures for Rabies may include:

  • Vaccinate household or domestic pets against the Rabies virus
  • Individuals who work in certain high-risk occupations, such as zookeepers or lab technicians, must get vaccinated for adequate protection
  • Individuals who travel to endemic regions with a high rate of Rabies infection should also get vaccinated

Preventable treatment of the Rabies virus is recommended, if the attending physician believes an individual has an increased risk of exposure to Rabies.

What is the Prognosis of Rabies? (Outcomes/Resolutions)

  • Individuals who have been bitten by an infected animal may still prevent Rabies, if suitable vaccinations are administered on time. Studies have shown that currently, no individual has developed Rabies with prompt and appropriate immunization
  • Individuals who begin to exhibit the signs and symptoms of Rabies, even with treatment, rarely survive the infection. Respiratory failure is the leading cause of death of individuals infected with the Rabies virus worldwide

Additional and Relevant Useful Information for Rabies:

  • More than 55,000 individuals in over 150 countries die each year from complications associated with the Rabies virus. This is usually because human rabies vaccines and immunoglobulin therapy are not readily available or within accessible reach
  • In the United States, animals that are most likely to transmit the Rabies virus include wild animals such as bats, coyotes, foxes, raccoons, and skunks
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Krish Tangella MD, MBA

Pathology, Medical Editorial Board, DoveMed Team


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