Rabies

Rabies kills nearly tens of thousands of people worldwide each year, yet many remain unaware of its serious nature until it's too late. This deadly virus attacks the nervous system and becomes fatal once symptoms appear. This comprehensive guide explains everything about rabies infection, including its causes, symptoms, and various rabies prevention and treatment approaches.

What is Rabies?

Rabies is a serious viral disease that attacks the central nervous system (CNS), affecting humans and animals. Rabies disease is caused by the rabies virus (RABV), primarily transmitted through the bite or saliva of infected animals, typically entering the body through bites, scratches, or contact with open wounds.

The vaccine-preventable condition presents itself in two distinct forms: 

• Furious rabies, the more common rabies type, causes hyperactivity, excitable behaviour, and distinctive symptoms like fear of water (hydrophobia) and fear of fresh air (aerophobia). 
• Paralytic rabies, accounting for about 20% of human cases, progresses more slowly with gradual muscle paralysis.

Symptoms of Rabies

The symptoms of rabies typically develop in stages, with an incubation period that can range from a few days to over a year. However, most cases show signs within 1-12 weeks after exposure.

The initial phase begins with symptoms that might be mistaken for common illnesses. Patients experience:

• Fever and headache
• Muscle aches and fatigue
• Loss of appetite
• Tingling or itching at the bite site
• A general feeling of unwellness

As the virus progresses to the central nervous system, it manifests in two distinct forms. Furious rabies, the more common type, causes:

• Aggressive behaviour
• Agitation and restlessness
• Hallucinations
• Excessive salivation
• Fear of water (hydrophobia)
• Fear of drafts (aerophobia)
• Seizures and muscle spasms
• Muscle twitching (fasciculations)

Paralytic rabies, accounting for approximately 20% of cases, presents differently. This form progresses more slowly, with muscles gradually becoming paralysed, starting from the wound site. Patients may experience weakness, tingling sensations, neck stiffness, and eventual coma development.

Causes of Rabies

The rabies virus (RABV) primarily spreads through the saliva of infected animals, typically entering the body through bites or when infected saliva comes into contact with open wounds or mucous membranes. While dogs are responsible for 99% of human rabies cases globally, the risk landscape varies by region, with other animals like bats, raccoons, or foxes playing a significant role in some areas.

Several factors can increase an individual's risk of rabies exposure:

• Living or travelling in developing countries where rabies is more common
• Activities involving contact with wild animals, such as cave exploration
• Occupational exposure, particularly veterinarians and laboratory workers
• Wounds to the head or neck which can accelerate virus progression to the brain

Complications of Rabies

Furious rabies leads to severe neurological complications, including:

• Uncontrollable hyperactivity
• Frightening hallucinations
• Complete loss of coordination
• Intense fear of water (hydrophobia)
• Extreme fear of fresh air (aerophobia)
• Various heart rhythm abnormalities and potential heart failure
• Breathing difficulties, oxygen deficiency, and pneumonia

Paralytic rabies progresses more slowly, with muscles gradually becoming paralysed from the infection site before leading to coma development.

Diagnosis

Diagnosing rabies presents unique challenges, as no single test can confirm the infection before symptoms appear. Doctors must conduct multiple tests on various samples to reach a definitive diagnosis.

• Direct Fluorescent Antibody (DFA): The DFA test serves as the gold standard for rabies diagnosis, offering accurate results within 1-2 hours. This test examines brain tissue samples using specialised fluorescent microscopy techniques to detect the presence of rabies virus antigens.
• Additional Testing:
  • Saliva analysis
  • Spinal fluid examination
  • Skin biopsies from neck hair follicles
  • Serum testing
• LN34 PCR Test: A newer diagnostic tool, this test uses real-time reverse transcriptase technology to detect viral genetic material. This innovative method proves particularly useful for testing decomposed or preserved tissues that might not be suitable for other diagnostic techniques.

Rabies Treatment

The primary approach is Post-exposure Prophylaxis (PEP), which must be administered as quickly as possible after potential exposure.

The PEP protocol consists of several crucial components:

• Immediate and thorough wound cleaning with soap and water
• Administration of human rabies immune globulin (HRIG)
• A course of rabies vaccines over 14 days

For individuals who have never received rabies vaccination before, the treatment includes both HRIG and four doses of rabies vaccine administered over two weeks. The HRIG provides immediate protection while the body develops its immune response to the vaccine.

Previously vaccinated individuals require a different protocol, consisting of only two vaccines given three days apart. They do not need HRIG as their bodies can mount a faster immune response due to previous vaccination.

The first dose of vaccine should be given as soon as possible after exposure, with subsequent doses following a strict schedule on days 3, 7, and 14. An additional fifth dose may be recommended on day 28 for people with compromised immune systems.

When to See a Doctor

Immediate emergency care is essential for severe bites, especially those near the head or neck, or exposures involving high-risk animals like bats, raccoons, skunks, or foxes. Even if someone isn't sure about being bitten, they should seek medical attention. 

Prevention

Essential rabies prevention strategies include:

• Keep pets' vaccinations current, especially for dogs and cats over four months of age
• Avoid contact with wild or stray animals, particularly in rabies-endemic areas
• Make properties unattractive to wild animals by securing trash bins and sealing entry points
• Seek immediate medical attention after potential exposure
• Consider pre-exposure vaccination if in high-risk occupations

Conclusion

Rabies remains one of the deadliest diseases known to medical science, yet proper understanding and quick action can prevent its fatal consequences. The disease kills nearly thousands of people annually, making prevention and awareness crucial tools in the fight against this virus.

Medical advances have made rabies preventable through proper vaccination and timely post-exposure treatment. People should wash any animal bite thoroughly with soap and lukewarm water, seek immediate medical care, and follow the prescribed vaccination schedule. These simple steps, combined with keeping pets vaccinated and avoiding contact with wild animals, can prevent most rabies cases.

FAQs

1. What happens when you get rabies?

The rabies virus travels slowly through nerve cells to reach the brain. Infected individuals show no symptoms during the incubation period, which typically lasts 2-3 months. Once the virus reaches the brain, it causes inflammation, leading to neurological symptoms if untreated.

2. How does rabies affect your body?

The virus primarily attacks the central nervous system, causing progressive damage. Effects include:

• Initial flu-like symptoms
• Nerve damage at the bite site
• Brain inflammation
• Behavioural changes
• Progressive paralysis

3. What animals are you most likely to get rabies from?

Globally, dogs are responsible for 99% of human rabies transmissions. Raccoons, bats, and foxes are the primary carriers in regions like the Americas. Raccoons remain the most frequently reported rabid animals, particularly in southeastern and northeastern areas. 

4. What happens if you get rabies?

Without rabies virus treatment, the virus causes fatal inflammation of the brain and spinal cord. The disease progresses through distinct phases, from early flu-like symptoms to either furious or paralytic rabies. Once symptoms appear, the condition is almost always fatal.

5. When to take the rabies vaccine?

Vaccination should begin immediately after potential exposure to the virus. The post-exposure treatment includes four doses over two weeks for previously unvaccinated individuals. For those previously vaccinated, only two doses are required.

6. Why can't rabies be cured?

The rabies virus becomes untreatable once it reaches the brain because the blood-brain barrier (BBB) protects it. This natural defence mechanism prevents medications from reaching the virus, making the disease fatal once symptoms appear.

Dr. Chaitanya Challa

MBBS, MD (Internal Medicine), PDCC (Critical Care), FCCS (Critical Care), Diploma in Endocrinology and Diabetes
CARE Hospitals Outpatient Centre, Banjara Hills, Hyderabad

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