Rabies

Causes Of Rabies

Rabies is caused by the rabies virus, which primarily spreads from infected animals to humans. The virus is present in the saliva, brain, and spinal cord of infected animals, making them the main source of transmission. 

Rabies can affect various mammals, including dogs, cats, bats, monkeys, foxes, raccoons, skunks, jackals, and mongooses. 

However, dogs are the most common source of rabies transmission to humans.

Transmission

When an infected animal bites, the rabies virus is transmitted through its saliva into the person’s body. Rabies can also spread through the following:

• Bites from an infected animal

• Scratches from the claws of an infected animal

• Exposure to infected saliva through the nose, eyes, mouth, or broken skin

The rabies virus can also be transmitted from human to human through the transplantation of organs, such as the cornea. While this type of transmission is rare, it is possible. As a result, the corneas and other organs from a person who has died from rabies should not be used for transplantation.

Note: Rabies is not spread by petting or touching dried saliva, blood, urine, or feces of a rabid animal.

Symptoms Of Rabies

Symptoms of rabies can be divided into the following stages: 

Stage 1 (Incubation): It is the period from exposure to the virus to the onset of symptoms and differs from person to person. This time is generally 2 to 3 months, but may range from 1 week to 1 year. It is dependent on factors such as the site of entry of the virus and the viral load

Stage 2 (Prodrome): This stage consists of nonspecific symptoms that mostly resemble the flu, with several gastrointestinal symptoms:

• Fever
• Headache
• Malaise
• Decrease in appetite
• Pain, numbness, tingling, and itching at the wound site

Stage 3 (Neurological): In this stage, the virus reaches the central nervous system. It causes fatal inflammation of the brain and spinal cord, which can be experienced as the following symptoms: 

• Anxiety
• Confusion
• Agitation
• Delirium
• Disturbed behavior
• Hallucinations
• Hydrophobia (fear of water) 
• Insomnia
• Muscle aches
• Weak arms and legs
• Difficulty in swallowing
• Aerophobia (fear of fresh air)

Stage 4 (Coma): This stage usually develops within ten days of stage 3. Patients may have consistent hydrophobia and can develop paralysis. 

Stage 5 (Death): Stage 4 can lead to death within 2 to 3 days without supportive care.

Risk Factors For Rabies

Low knowledge levels regarding rabies

Rabies is highly prevalent in areas where people have low knowledge regarding rabies and dog bites. The cases are especially seen in rural areas where people are unaware of the measures taken to prevent and manage rabies. 

Exposure to unvaccinated dogs

Dogs are the main source of spreading rabies. Exposure to stray dogs or unvaccinated dogs can be a source of infection. 

Living in rabies-endemic countries

People living in rabies-endemic countries with poor control of dogs and wildlife are more prone to rabies infection. 

Age

Children are at high risk of catching the virus as they are more prone to being attacked by animals. Most cases of rabies are seen in children bitten by dogs, especially on their arms and faces. 

Occupation or activities

Veterinarians, animal handlers, lab workers, and outdoor adventurers like campers or spelunkers are at higher risk of rabies due to close contact with potentially infected animals.

Delayed or inadequate post-exposure treatment

Not washing the wound immediately and not receiving timely and appropriate post-exposure prophylaxis (PEP) pose a high risk for rabies.

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Diagnosis Of Rabies

Immediate medical attention

Immediate medical attention is crucial if a person is suspected of being bitten or scratched by an animal, as there is no definitive way to identify a rabid animal just by appearance.

Limitations of diagnostic testing

Although diagnostic tests can confirm rabies infection, they often take time. Relying solely on test results can delay treatment, which is dangerous since rabies is almost always fatal once symptoms appear.

Testing the animal

If the biting or scratching animal is available, it is typically tested for rabies. This can prevent unnecessary physical, emotional, and financial stress for the exposed individual if the animal is not found to be rabid.

• Direct Fluorescent Antibody (DFA) Test: The DFA test is the gold standard for diagnosing rabies in animals. It detects rabies virus antigens in the brain tissue of an animal that has been humanely euthanized.
  
  

• Observation period: If the animal (especially a dog or cat) is healthy and vaccinated, it is usually observed for 10 days. If the animal remains healthy during this time, no treatment may be necessary. Final decisions are typically made in consultation with the local health department.
  
  

Testing in humans

Rabies in humans is confirmed using various tests that detect the virus, its antigens, or genetic material in body tissues. Common diagnostic methods include:

• Lumbar puncture: A sample of cerebrospinal fluid (CSF) is collected from the lower spine using a thin needle. This fluid is tested for the presence of the rabies virus.
  
  

• Nuchal skin biopsy: This is the most reliable method during the first week of infection. A skin sample from the back of the neck is examined using immunofluorescent staining to detect rabies virus antigens in nerve fibers.
  
  

• Real-time polymerase chain reaction (RT-PCR): Saliva samples are tested using RT-PCR to detect rabies RNA. This test amplifies the virus’s genetic material and is considered highly sensitive and confirmatory.
  
  

Blood tests

Blood tests are not typically used to detect active rabies infection, as virus-specific antibodies take time to appear. Instead, they are mainly used to:

• Assess the body’s immune response to rabies vaccination.

• Common antibody tests include:

  • Fluorescent Antibody Virus Neutralization (FAVN) Test

  • Rapid Fluorescent Focus Inhibition Test (RFFIT)
    
    

Imaging tests

Imaging is not used to confirm rabies but may help identify rabies-related encephalitis:

• Magnetic resonance imaging (MRI): Uses magnetic fields and radio waves to create detailed brain images.
  
  

• Computed tomography (CT) scan: Uses X-rays to create detailed images of the brain to detect inflammation or other abnormalities.

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Specialist To Visit

Rabies is a medical emergency and can lead to fatal consequences if not treated promptly. Any bite or scratch from an unfamiliar or wild animal should never be ignored. Immediate action is crucial.

Doctors typically evaluate the wound and decide the course of treatment based on the severity of the animal attack. The following specialists are involved in the diagnosis and treatment of rabies:

• General Physician
• Infectious disease specialist
• Neurologist

A general physician is typically the first point of contact for rabies exposure. They will assess the wound and determine the need for post-exposure prophylaxis (PEP).

If rabies exposure is suspected, an infectious disease specialist can provide more detailed guidance on the virus, including preventive treatment and further diagnostic tests.

If the disease progresses to neurological symptoms, a neurologist may be consulted for the management of complications affecting the brain and nervous system.

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Prevention Of Rabies

Eliminating rabies in animals

Rabies is a preventable disease through vaccination. It's crucial to keep your dogs, cats, ferrets, and certain livestock up to date with their rabies vaccinations. If your dog or cat is bitten or attacked by a wild animal, a booster shot is also recommended.

Pre-exposure rabies vaccination 

Pre-exposure rabies vaccination is given to individuals who are at high risk of being exposed to the rabies virus. These include:

• Veterinarians and animal handlers
• Veterinary students
• Laboratory workers dealing with rabies or related viruses
• Wildlife researchers or explorers
• People traveling to rabies-endemic regions
• Children in rabies-endemic areas 

Vaccination schedule for pre-exposure:

• Intramuscular (IM): Three doses on days 0, 7, and 21 or 28.

• Intradermal (ID): Three doses on days 0, 7, and 21 or 28. (Note: The intradermal route is more common in India because it uses a lower vaccine volume and is cost-effective.)

Post-exposure rabies vaccination

Post-exposure rabies vaccination is a critical step for individuals who have been bitten, scratched, or otherwise exposed to the saliva of an animal suspected of having rabies. Immediate treatment after exposure can prevent the disease from progressing.

Vaccination schedule for post-exposure:

For individuals who have never been vaccinated:

• Day 0: First dose (immediately after exposure)
• Day 3: Second dose
• Day 7: Third dose
• Day 14: Fourth dose
• Day 28: Fifth dose (optional, depending on the type of exposure)

For individuals previously vaccinated (pre-exposure):

• Day 0: First dose
• Day 3: Second dose
  
  

Rabies Immunoglobulin (RIG) may be administered alongside the vaccine if the individual has never been vaccinated previously. This provides immediate passive immunity and must be given as soon as possible after exposure, ideally within 24 hours.

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Avoiding animal exposure

The best way to prevent rabies is to avoid contact with potentially infected animals. Follow these precautions:

• Don’t touch injured or stray animals—report them to local authorities.

• Avoid feeding, petting, or playing with unfamiliar animals, especially in high-risk areas.

• Don’t allow your pets to roam freely.

• Store garbage and pet food securely to avoid attracting wild or stray animals.

• Don’t keep wild animals as pets.

• Report any unusual behavior in your pets to a veterinarian immediately.

• Teach children not to touch or feed stray animals and to report any bites or scratches.

Rabies awareness

Understanding the risk and severity of rabies is essential. Rabies is almost always fatal once symptoms appear, but it is completely preventable with timely medical care and vaccination.

Education plays a vital role in reducing rabies risk. Raising awareness in communities should include:

• The importance of responsible pet ownership

• How to prevent dog bites

• First aid measures after a bite or scratch

• The need for prompt medical care after exposure.
  
  

Teaching both adults and children about rabies prevention helps reduce exposure and saves lives.

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Treatment Of Rabies

Rabies is almost always fatal once clinical symptoms appear. However, immediate and appropriate medical treatment after exposure can effectively prevent the disease from progressing. 

Immediate first aid: The first line of defense

If bitten or scratched by an animal suspected to be rabid:

• Wash the wound immediately and thoroughly with soap and running water for at least 15 minutes. This helps reduce the viral load at the site.

• Apply antiseptic (e.g., povidone-iodine, iodine solution, or alcohol) after washing.

• Seek medical attention immediately.
  
  

Do not delay. Even minor scratches or licks on broken skin can transmit the rabies virus.

Post-exposure prophylaxis (PEP)

PEP is essential for preventing rabies after potential exposure. It consists of:

1. Rabies vaccine

Unvaccinated individuals:

• 5-dose schedule on days 0, 3, 7, 14, and 28

Previously vaccinated individuals:

• Only 2 doses on days 0 and 3
• No need for Rabies Immunoglobulin (RIG)
  
  

2. Rabies immunoglobulin (RIG)

• Given only to unvaccinated individuals

• Should be administered as soon as possible after exposure

• Infiltrated into and around the wound site
  
  

No effective treatment after the onset of symptoms

Once symptoms (such as fever, anxiety, difficulty swallowing, hydrophobia, or confusion) appear, rabies is almost always fatal. At this stage:

• Treatment becomes supportive only (palliative care)

• Patients may receive sedation, ventilation, and comfort care

• No antiviral drug or therapy has been proven effective
  
  

Prevention is the best treatment

Since there is no cure once symptoms begin, prevention through vaccination (pre- and post-exposure) and public awareness is crucial.

Complications Of Rabies

Once the rabies virus enters the body, it travels through the peripheral nervous system (PNS) toward the central nervous system (CNS), particularly the brain, where it causes severe and often irreversible neurological complications such as encephalomyelitis (inflammation of the brain and spinal cord).

As the virus spreads, it can lead to psychiatric and neurological symptoms, including:

• Anxiety

• Agitation

• Delirium

After affecting the CNS, the virus can travel back to the peripheral nervous system, targeting peripheral organs, most notably the salivary glands, which facilitates the virus's transmission through saliva.

If not treated promptly, rabies can result in complete nervous system failure, often leading to death. The following complications may develop in infected individuals:

• Seizures

• Fasciculations (muscle twitching)

• Psychosis

• Aphasia (loss of ability to speak or understand language)

• Autonomic instability (irregular heartbeat, temperature, and blood pressure regulation)

• Paralysis, including paralysis of the lower limbs

• Coma

• Confusion

• Difficulty swallowing (due to painful throat and laryngeal spasms)

• Insomnia

• Apnea (temporary cessation of breathing)

• Cardiopulmonary complications, such as low blood pressure) and cardiac arrest

• Multiple organ failure

• Death.