Question

A 19-year-old student is bitten on the hand by an unusually aggressive dog while travelling in a rabies-endemic country in South America. He had not received rabies vaccination before travel. The wound has been thoroughly washed and irrigated. What is the most appropriate next step?

a. Give full rabies vaccination only
b. Give human rabies immunoglobulin + full course of vaccination
c. Reassure him that rabies risk is negligible and give antibiotics only
d. Give human rabies immunoglobulin alone
e. Give tetanus booster and observe for neurological symptoms

Answer

b. Give human rabies immunoglobulin + full course of vaccination

Detailed explanation

This man has had a possible rabies exposure in a rabies-endemic country and was not previously immunised. After immediate wound cleansing, he needs both:

1. Human rabies immunoglobulin, HRIG
2. Full course of rabies vaccination

Rabies immunoglobulin provides immediate passive immunity by neutralising virus at the wound site before the patient’s own immune system has responded.

Rabies vaccine provides active immunity, allowing the patient to generate protective antibodies over the following days and weeks.

The key principle is:

Previously unimmunised + significant rabies exposure = HRIG + full vaccine course

If possible, as much HRIG as anatomically feasible should be infiltrated around and into the wound, with the remainder given intramuscularly at a site distant from the vaccine injection site.

Rabies is almost invariably fatal once clinical symptoms develop, so post-exposure prophylaxis must be given promptly when exposure risk is significant.

Why the other options are wrong

a. Give full rabies vaccination only
This is incomplete for a previously unimmunised person after a significant exposure. Vaccine takes time to induce antibodies, so immediate passive protection with HRIG is also needed.

c. Reassure him that rabies risk is negligible and give antibiotics only
This dangerously underestimates the risk. A dog bite in a rabies-endemic area is a significant exposure. Antibiotics may be needed for bacterial bite infection prevention, but they do not prevent rabies.

d. Give human rabies immunoglobulin alone
HRIG gives short-term passive protection only. It does not create durable active immunity. Vaccination is essential.

e. Give tetanus booster and observe for neurological symptoms
Tetanus status should be considered after animal bites, but observation for rabies symptoms is unsafe. Once rabies symptoms appear, the disease is almost always fatal.

Key exam point

After possible rabies exposure in a non-immunised patient, give human rabies immunoglobulin plus a full course of rabies vaccine after urgent wound washing.

Very important clinical trap

Do not give vaccine alone to a previously unimmunised patient after high-risk exposure. Vaccine alone is appropriate only in some lower-risk or previously vaccinated scenarios. HRIG is needed for immediate protection in unimmunised patients with significant exposure.

Cheat sheet for exam

• Rabies virus: RNA virus, Rhabdovirus family, Lyssavirus genus.
• Shape: bullet-shaped virion.
• Main global source: dog bites.
• Other possible sources: bats and wild carnivores depending on region.
• Incubation: variable, often weeks to months.
• Virus replicates locally in muscle, then travels via peripheral nerves to CNS.
• Causes acute encephalitis.
• Classic symptoms: fever, headache, agitation, hydrophobia, hypersalivation.
• Hydrophobia = painful pharyngeal spasms triggered by attempts to drink.
• Negri bodies: cytoplasmic inclusions in infected neurons.
• Once symptomatic, rabies is almost always fatal.
• Immediate management: wash and irrigate wound thoroughly.
• Previously vaccinated: give booster vaccine doses.
• Not previously vaccinated: HRIG + full vaccine course.
• HRIG should be infiltrated around the wound where possible.
• Vaccine and HRIG should be given at different anatomical sites.
• Antibiotics may be needed for bite infection, but do not replace rabies prophylaxis.

Flash cards

Q: What is the most important first step after a possible rabies exposure?
A: Immediate thorough wound washing and irrigation. This reduces viral inoculum at the site of entry.

Q: What post-exposure prophylaxis is needed in an unimmunised patient after a high-risk rabies exposure?
A: Human rabies immunoglobulin plus full rabies vaccination course.

Q: Why is HRIG given after rabies exposure?
A: It provides immediate passive immunity by neutralising virus before vaccine-induced antibodies develop.

Q: Why is rabies vaccine still required if HRIG is given?
A: HRIG is temporary passive protection; vaccine induces active long-term immunity.

Q: What is the classic symptom of rabies involving water?
A: Hydrophobia, caused by painful pharyngeal spasms triggered by drinking or seeing water.

Q: What are Negri bodies?
A: Cytoplasmic inclusion bodies found in neurons infected with rabies virus.

Q: What is the prognosis once clinical rabies develops?
A: Almost universally fatal.

Q: What family does rabies virus belong to?
A: Rhabdoviridae; it is a lyssavirus.

MCQs

1. A 25-year-old unvaccinated traveller is bitten deeply on the leg by a stray dog in a rabies-endemic country. The wound is cleaned thoroughly. What is the best next management?

a. Rabies vaccine only
b. Human rabies immunoglobulin only
c. Human rabies immunoglobulin plus full rabies vaccination course
d. Oral co-amoxiclav only
e. Observe the animal and treat only if the patient develops symptoms

Answer: c. Human rabies immunoglobulin plus full rabies vaccination course

Explanation: An unimmunised patient with significant possible rabies exposure needs both passive immunity with HRIG and active immunity with vaccination. Waiting for symptoms is unsafe because symptomatic rabies is almost always fatal.

2. Which of the following is false regarding rabies?

a. It can cause acute encephalitis
b. It is an RNA virus
c. It commonly produces hydrophobia
d. It is usually benign once symptoms develop
e. It may be transmitted by animal bites

Answer: d. It is usually benign once symptoms develop

Explanation: This is false. Rabies is almost invariably fatal after clinical disease develops. Prevention after exposure is therefore critical.

3. A previously vaccinated traveller is bitten by a potentially rabid animal abroad. What is usually required after wound cleansing?

a. Full vaccine course plus HRIG
b. Booster rabies vaccine doses without HRIG
c. HRIG alone
d. Antibiotics only
e. No treatment if vaccinated more than 10 years ago

Answer: b. Booster rabies vaccine doses without HRIG

Explanation: Previously immunised patients usually require additional vaccine doses but not HRIG, because they should mount a rapid anamnestic immune response.

4. What is the main purpose of infiltrating rabies immunoglobulin around the bite wound?

a. To reduce bacterial cellulitis
b. To improve wound healing
c. To neutralise rabies virus locally before neural spread
d. To induce long-term antibody memory
e. To prevent tetanus toxin release

Answer: c. To neutralise rabies virus locally before neural spread

Explanation: HRIG is passive antibody. Its main role is local neutralisation of virus at the inoculation site before the virus enters peripheral nerves.

5. Which finding is classically associated with rabies infection?

a. Donovan bodies
b. Reed-Sternberg cells
c. Negri bodies
d. Aschoff bodies
e. Councilman bodies

Answer: c. Negri bodies

Explanation: Negri bodies are eosinophilic cytoplasmic inclusions found in neurons in rabies infection, classically in hippocampal and cerebellar neurons.

6. Which of the following best describes the pathogenesis of rabies after a bite?

a. Direct bloodstream spread to liver followed by hepatic failure
b. Local replication followed by peripheral nerve spread to the CNS
c. Immediate destruction of red blood cells
d. Toxin-mediated blockade of neuromuscular junctions
e. Immune complex deposition in renal glomeruli

Answer: b. Local replication followed by peripheral nerve spread to the CNS

Explanation: Rabies virus replicates near the inoculation site, then travels via peripheral nerves to the CNS, causing encephalitis.

7. Which of the following is false about post-exposure rabies management?

a. The wound should be washed thoroughly
b. HRIG is indicated in unimmunised patients with significant exposure
c. Vaccine generates active immunity
d. HRIG and vaccine are unnecessary once the wound is cleaned
e. HRIG should be given around the wound if possible

Answer: d. HRIG and vaccine are unnecessary once the wound is cleaned

Explanation: Wound cleaning is essential but not sufficient for significant exposure in an unimmunised person. HRIG and vaccine are still required.

8. A patient develops fever, agitation, hypersalivation and painful throat spasms when attempting to drink after a dog bite several weeks earlier. What symptom is being described?

a. Photophobia
b. Hydrophobia
c. Aerophagia
d. Dysarthria
e. Trismus

Answer: b. Hydrophobia

Explanation: Hydrophobia is a classic feature of rabies, caused by pharyngeal muscle spasms triggered by attempts to swallow liquids.

9. Which statement best explains why rabies vaccine alone is inadequate immediately after high-risk exposure in an unimmunised person?

a. Rabies vaccine has no role after exposure
b. Vaccine causes immunosuppression in the first week
c. Vaccine-induced antibodies take time to develop
d. Vaccine only works against bat-associated rabies
e. Vaccine is only useful before travel

Answer: c. Vaccine-induced antibodies take time to develop

Explanation: HRIG bridges the vulnerable early period before vaccine-induced active immunity develops.

10. Which of the following is the most accurate exam statement?

a. Rabies is usually transmitted by contaminated water
b. Rabies is a DNA herpesvirus
c. Rabies is mostly harmless if treated after neurological symptoms appear
d. Rabies post-exposure prophylaxis depends partly on previous vaccination status
e. HRIG alone gives lifelong immunity

Answer: d. Rabies post-exposure prophylaxis depends partly on previous vaccination status

Explanation: Previously immunised patients usually need booster vaccine doses; unimmunised patients with significant exposure need HRIG plus vaccine.

Summary for quick exam revision

Rabies is an acute viral encephalitis caused by an RNA lyssavirus from the Rhabdoviridae family. The virus has a bullet-shaped capsid and is classically transmitted through infected animal bites, especially dog bites worldwide. After inoculation, the virus replicates locally in muscle before entering peripheral nerves and travelling to the central nervous system. Clinical rabies may begin with fever, headache and agitation, then progress to hydrophobia, hypersalivation, encephalitis and death. Hydrophobia occurs because attempts to swallow trigger painful pharyngeal spasms. Negri bodies are cytoplasmic inclusion bodies found in infected neurons. The crucial exam principle is that rabies is almost always fatal once symptoms appear, so prevention after exposure is urgent. The wound should first be thoroughly washed and irrigated. In a previously immunised person, post-exposure management usually involves further vaccine doses. In a person who has not been previously immunised and has a significant possible exposure, management is human rabies immunoglobulin plus a full course of rabies vaccination. HRIG provides immediate passive immunity and should be infiltrated around the wound if possible. The vaccine provides active immunity and long-term antibody protection. Antibiotics may be appropriate for bacterial infection after an animal bite, but they do not prevent rabies. The dangerous exam trap is choosing vaccine alone in an unimmunised patient after a high-risk exposure.