Rabies

Rabies is a zoonotic disease, meaning it can be transmitted from animals to humans. It is caused by a virus that attacks the central nervous system, leading to severe neurological symptoms and, if left untreated, almost invariably death. While rabies is a global concern, it is preventable with appropriate vaccination. 

Rabies is a viral disease that affects the central nervous system of mammals, including humans. It's caused by the rabies virus, a member of the Rhabdoviridae family, known for its bullet-like shape under a microscope. This virus has a particular affinity for nerve tissue, and once it enters the body, it begins a journey to the brain.   

The virus typically enters through a bite or scratch from an infected animal, their saliva carrying the infectious agent. Less commonly, it can enter through existing wounds or mucous membranes (eyes, nose, mouth) that come into contact with infected saliva. Once inside, the virus doesn't immediately attack. It has a variable incubation period, ranging from weeks to months, even years in rare instances, during which it replicates locally at the entry site before affecting the brain.   

Once it reaches the brain, it causes encephalitis – a severe inflammation that disrupts normal brain function. This leads to the classic neurological symptoms associated with rabies. 

The tragic aspect of rabies is that once clinical symptoms appear, it's almost always fatal. Therefore, prevention and post-exposure prophylaxis to stop the virus are extremely important.

Worldwide:

• Rabies causes an estimated 59,000 human deaths annually, primarily in Asia and Africa.
• Over 95% of human deaths occur in developing countries.
• Children are disproportionately affected, accounting for 40% of rabies deaths.

India:

• India has one of the highest rabies burdens in the world, contributing to approximately 36% of global rabies deaths.
• Dogs and rabies are strongly related as dogs are the main source of rabies transmission in India.

While there are no distinct "types" of rabies, the disease can manifest in two clinical forms:

• Furious Rabies: This is the more common form, characterized by hyperactivity, agitation, aggression, hallucinations, and hydrophobia (fear of water).
• Paralytic Rabies: This form presents with paralysis, starting at the site of the bite and progressing throughout the body. It can lead to coma and death.

The rabies virus is the sole culprit behind this deadly disease. It's primarily found in the saliva of infected animals, making bites the most common mode of transmission. Here's a deeper look at how the virus spreads:   

Animal Bites

When a rabid animal bites, its saliva, laden with the virus, enters the victim's tissues. The depth and location of the bite influence the risk of infection. Bites closer to the head and neck are particularly dangerous due to the proximity to the brain.   

Scratches and Abrasions

Even seemingly minor scratches from infected animals can transmit the virus if saliva contaminates the wound. Similarly, any open wound or abrasion that comes into contact with infected saliva poses a risk.   

Licks

While less common, licks from infected animals on broken skin or mucous membranes can also transmit the virus. This is particularly concerning with bats, as their small teeth can leave barely noticeable bites that may go unnoticed.   

Inhalation

In rare cases, rabies can be transmitted through inhalation of aerosolized virus, such as in bat caves.

Organ Transplantation

Although extremely rare, rabies transmission has been reported through organ transplantation from infected donors.   

Animals known to transmit rabies are:

• Dogs: Globally, dogs are the primary source of rabies transmission to humans. This is particularly true in countries where dog vaccination programs are not widespread.   
• Bats: Bats are a significant reservoir for rabies in many parts of the world, including the Americas and Europe. Their bites can be small and painless, making it difficult to identify potential exposures.   
• Wildlife: A variety of wild animals can carry and transmit rabies, including: 
  • Raccoons   
  • Skunks   
  • Foxes   
  • Mongooses   
  • Wolves   
  • Jackals

It's important to note that any mammal can potentially contract and transmit rabies. However, rodents (like rats and mice) and lagomorphs (like rabbits and hares) rarely transmit rabies to humans.  

The incubation period for rabies (time between exposure and symptom onset) can vary from weeks to months, even years in rare cases. Symptoms typically progress through several stages:

• Prodromal Stage:
  • Flu-like symptoms (fever, headache, muscle aches)
  • Pain or itching at the bite site
  • Anxiety, irritability, and insomnia
• Acute Neurological Stage:
  • Furious rabies: Hyperactivity, agitation, aggression, hallucinations, hydrophobia (fear of water), aerophobia (fear of drafts), and hypersalivation.
  • Paralytic rabies: Ascending paralysis (starting from the bite site and moving upwards), weakness, and difficulty swallowing.
• Coma and Death: If untreated, rabies progresses to coma and ultimately death due to respiratory failure or cardiac arrest.

Diagnosing rabies in a living person is challenging, especially in the early stages when symptoms are non-specific. There's no single test that can definitively confirm rabies infection before symptoms become severe. Doctors rely on a combination of factors to make a diagnosis:   

• Detailed Exposure History: This is perhaps the most crucial aspect of rabies diagnosis. Doctors will meticulously inquire about:
  • Animal encounters: Any bites, scratches, or licks from animals in the recent past, even seemingly minor incidents.   
  • Animal species: The type of animal involved (e.g., dog, bat, raccoon) and its behaviour (e.g., aggressive, unprovoked attack).
  • Geographic location: Where the exposure occurred, as rabies prevalence varies in different regions.   
  • Vaccination status of the animal: Whether the animal was known to be vaccinated against rabies.
• Clinical Presentation: As the disease progresses, characteristic symptoms may emerge, aiding in diagnosis:
  • Neurological symptoms: Anxiety, agitation, confusion, hallucinations, hydrophobia (fear of water), aerophobia (fear of drafts), paralysis, and seizures.   
  • Symptoms at the bite site: Pain, itching, or tingling at the site of the bite.   
• Laboratory Investigations: Several tests can be used to support the diagnosis, but none are conclusive on their own in living humans:
  • Saliva testing: Detecting viral RNA in saliva through polymerase chain reaction (PCR) testing.   
  • Skin biopsy: Examining a skin biopsy from the nape of the neck for rabies antigen using direct fluorescent antibody (DFA) testing.   
  • Antibody testing: Checking for rabies antibodies in blood or cerebrospinal fluid (CSF). This is more useful later in the course of the disease.   
  • Ante-mortem brain biopsy: While rarely performed, a brain biopsy can be considered in certain cases to detect the virus.
• Post-mortem Testing: Unfortunately, the most definitive diagnosis of rabies often occurs after death. Post-mortem examination of brain tissue using DFA testing is the gold standard for confirming rabies infection.   

The difficulty in definitively diagnosing rabies in living humans highlights the importance of post-exposure prophylaxis (PEP) after any potential exposure. It's better to err on the side of caution and receive PEP than to wait for confirmatory tests, as delaying treatment can be fatal.

There is no effective rabies virus treatment once clinical symptoms appear. The disease progresses relentlessly, leading to severe neurological damage and ultimately death. However, prompt post-exposure prophylaxis (PEP) can prevent the virus from reaching the brain and causing disease. PEP is highly effective if administered correctly and in a timely manner.   

Components of Rabies Post-Exposure Prophylaxis (PEP):

• Local Wound Treatment:
  • Immediate and thorough cleaning: The wound should be washed immediately and thoroughly with soap and water for at least 15 minutes. This helps to physically remove the virus.   
  • Antiseptic application: An antiseptic solution, such as povidone-iodine or ethanol, should be applied to the wound to further reduce the viral load.   
• Rabies Vaccination:
  • Inactivated rabies vaccine: Modern rabies vaccines are inactivated, meaning they contain killed rabies virus that cannot cause disease.   
  • Vaccination schedule: PEP typically involves a series of four doses of the rabies vaccine, administered intramuscularly on days 0, 3, 7, and 14.   
  • Booster doses: In some cases, a fifth dose may be recommended on day 28. Booster doses may also be needed for individuals who remain at high risk of exposure.
• Rabies Immune Globulin (RIG):
  • Passive immunity: RIG provides immediate but temporary protection by delivering ready-made antibodies against the rabies virus.   
  • Administration: RIG is infiltrated around the wound and any remaining dose is administered intramuscularly at a site distant from the vaccination site.   
  • Importance: RIG is crucial for providing immediate protection while the body develops its own immune response through vaccination.   

Factors Influencing PEP:

• Severity of exposure: The type of exposure (bite, scratch, lick), its location, and the depth of the wound.   
• Animal species: The type of animal involved and its vaccination status.   
• Rabies prevalence in the area: The risk of the animal being rabid.
• Vaccination history: Whether the individual has previously received rabies vaccination.

The effectiveness of PEP depends on how quickly it is administered after exposure. The sooner PEP is started, the better the chances of preventing the virus from reaching the brain. Ideally, PEP should be initiated within 24 hours of exposure, but it can still be beneficial even if started later.   

• Exposure to wildlife: Living in or travelling to areas with high rabies prevalence.
• Occupational exposure: Veterinarians, animal handlers, and wildlife professionals have an increased risk.
• Lack of vaccination: Not being vaccinated against rabies.
• Living in remote areas: Limited access to healthcare and PEP.

Once symptoms of rabies appear, complications are severe and often lead to death. These may include:

• Respiratory failure
• Cardiac arrest
• Brain damage
• Paralysis

• Start post-exposure treatment immediately—every hour counts.
• Complete the full vaccine and immunoglobulin course without skipping doses.
• Avoid self-medicating—follow your doctor’s instructions strictly.
• Rest and hydrate well to support your immune system.
• Stay away from potentially rabid animals to prevent further exposure.

Only wild animals carry rabies.

Domestic animals, like dogs and cats, can also transmit rabies.

Rabies can be cured.

There is no cure for rabies once symptoms appear.

All animal bites require rabies PEP.

The need for PEP depends on the type of animal, the circumstances of the bite, and the rabies prevalence in the area.

Seek immediate medical attention after any potential exposure to rabies, especially if:

• You are bitten or scratched by an animal (especially a wild animal or an unvaccinated domestic animal).
• You have contact with an animal's saliva on broken skin or mucous membranes.
• You are travelling to a rabies-endemic area.

• Do I need rabies post-exposure prophylaxis?
• What does the rabies vaccination involve?
• What are the side effects of the rabies vaccine?
• What are the signs and symptoms of rabies?
• What should I do if I am bitten by an animal in the future?

Supporting a rabies patient is primarily about providing emotional support and comfort during a difficult time. Since the prognosis is poor once symptoms appear, focus on:

• Offering compassion and empathy: Listen to their fears and concerns and provide emotional support.
• Helping with practical matters: Assist with tasks like contacting family members or arranging for medical care.
• Respecting their wishes: Follow their preferences regarding treatment and end-of-life care.

Rabies is a devastating disease, but it is preventable. By understanding the risks, taking preventive measures like vaccination, and seeking immediate medical attention after potential exposure, we can protect ourselves and our communities from this deadly virus.