Understanding Rabies: Transmission, Prevention, and Treatment

Rabies is a deadly but preventable virus spread to people from the saliva of infected animals. It is a rare condition because vaccines are widely available.

Rabies is an important topic for PSM. Read this blog thoroughly to elevate your NEET PG exam preparation. 

• Zoonotic disease. It has a maximum case fatality rate: 100% fatality rate. If someone bit by the rabid animal and post prophylaxis is not given on time, the person will die for sure without any escape. It doesn’t follow the iceberg phenomenon.

Epidemiological Determinants

1. Agents
   • Lyssavirus type 1 
     • Bullet shaped RNA virus.
     • Belongs to the Rhabdoviridae family.
2. Two Types of Viruses
   • Street virus
     • Responsible for Natural infection
     • Street Virus causes Rabies. 
   • Fixed virus
     • Not responsible for Natural infection.
     • Used for production of the Vaccine.
     • Does not demonstrate Negri bodies.

Host factors

• The dog bite mostly occurs in children and as well as adults 
• Age group: 1 to 24 years

Occupation

• Dog handlers
• Forest workers 
• Veterinarians.

Route of Transmission

• Animal bite: Dog bite, Cat bite, Monkey bite or Wild animal bite.
• They all require vaccination. In India, Urban Rabies is very common. Rodent bites don't require vaccination. Licks on abraded skin (integrity of the skin is broken) is also considered as the route of transmission. Aerosol (Rabies infected bats) transmission is very rare. In India, bat rabies (Aerosol mode transmission) is not reported.
• Human bite is very dangerous bite- no documented cases so far 

Categories of Exposure to Suspect or Confirmed Rabid Animal Bite

• Management depends on these categories only.
• There are 3 categories
  1. Category-1
  2. Category-2
  3. Category-3 
• Post exposure prophylaxis: Primary level of prevention.
  • The virus doesn’t get attached to the nerve endings and travel to the brain.

Categories of contact with suspect rabid animal	Post-exposure Prophylaxis
Category 1: Licks or touch on intact skin. The integrity of the skin is not broken.	Local wound management
Category 2: Minor scratch or Abrasions without bleeding. Integrity of the skin is broken.	Local wound management  Immediate Rabies vaccination
Category 3 It can be a single bite or multiple transdermal bites. Bleeding occurs. Licks on broken skin. Contamination of mucus membrane from the saliva through licks. Contact with bats. Wild animal bite.	Wound management  Rabies vaccination  Rabies immunoglobulin administration

Wound Management

• Wound must be kept under running water
• Wash it with soap and water for 10 to 15 minutes.
• Three purposes of Wound Management:
  1. Physical
  2. Chemical
  3. Biological 

Physical	Wash with running tap water	Mechanical removal of virus from wound
Chemical	Wash the wound with soap and water Apply disinfectants like tincture, Iodine.	Inactivation of virus
Biological	Infiltrate immunoglobulin in the depth and around the wound in Category 3 exposures	Neutralisation of Virus

Management of Animal Bite

Local Wound Treatment: It is done in all the categories 

• The wound must be kept under running water and washed with soap and water for 15 to 20 minutes. 
• Purpose- The virus must be removed and doesn’t get attached to the nerve endings. You can clean with alcohol and tincture. Don’t suture the wound because it may cause spreading of the virus. If suturing of a wound is required it will be done 24 to 48 hours later.

Rabies Vaccination (Post Exposure Prophylaxis Recommended Regimens)

• It can given both in the form of Intramuscular (IM) and Intradermal (ID). According to the Natural Rabies Control Program, Intradermal regimen is preferred over Intramuscular regimen, because the ID regimen is cost effective. The ID regimen is the updated THAI Red Cross regimen.

THAI Red Cross Regimen

• Intradermal regimen.
• Schedule: On Days: 0, 3, 7, 28 the Rabies vaccination is given. In the four visits, the vaccine is given on two sites simultaneously (2-2-2-2)
• In the IM regimen, the vaccine is also given on day 14.
  • It is given like 2-2-2-0-2. Meaning the vaccine is not given by ID route on day 14. Because on day 14, the vaccine is given through the IM route.
• Dose: 0.1ml. Total: 8 doses are given in this schedule.
• Day 0 is not the first day of dog bite.
  • Day 0 means the day when first dose of vaccination is administered.

Essen Regimen

• Intramuscular regimen 
• It has 5 visits: On days 0, 3, 7, 14, 28. It’s been given on one site only.. So, it is 1-1-1-1-1
• Site: 
  • For adults, it is given on the deltoid but not on the gluteal region.
  • For children, the Anterolateral aspect of the thigh.
• Dose: 0.5ml; one complete vial is used. Government is preferring to give in the Intradermal regimen whereas in private the Essen regimen is followed. This regimen is not cost effective.

Re- Exposure Guidelines

• Same person suffers from a dog bite again. It has 2 visits- on days 0, 3. Intramuscular or Intradermal regimens can be used.
• It can be divided into two:
  1. A dog bite again within 3 months-
     • No Vaccination required. Person is previously immunized. 
  2. A dog bite again beyond 3 months- 
     • Vaccination is required. Only 2 visits are needed- On days 0,3 through ID/IM. Do Not repeat immunoglobulins in Re exposure prophylaxis if it is administered prior (need not be repeated for life)

Pre-Exposure Guidelines

• Given to people at high risk
  • Veterinarians
  • Forest workers
  • Animal handlers
• 3 visits are required.
• Days: 0, 7, 21 or 28
• Route: IM or ID

Rabies Immunoglobulin

• It is given in category 3 bite. 
• In certain conditions, it is also given in category 2.
  • In HIV case 
  • Immunocompromised case
• Rabies Immunoglobulin is two types
  1. Equine immunoglobulin
     • Not preferred
     • It’s units are 20 IU/kg
  2. Human rabies Immunoglobulin
     • Preferred, given with 40 IU/kg.. It must be started on Day 0 along with vaccination. Can be given Up to 7 days (after that not required as antibodies start forming due to vaccination). Given through IM route
     • It is given 70% in and around the wound and the rest can be given distant from the wound.
• Immunoglobulin once given in life need not be repeated even in re-exposure cases.

Special Considerations

• No contraindication to post exposure prophylaxis as it is 100% fatal.
• Rabies vaccine be given in pregnancy, HIV, Immunocompromised, infants and children.
• Rabies vaccine is a killed vaccine.
• Individuals on chloroquine treatment for malaria - IM route is preferred as ID route reduces response of vaccine.
• Even if the bite is from a vaccinated pet dog – post exposure prophylaxis is given.
  • If the dog is observed and remains healthy for 10 days – continue and finish vaccination.
  • Day 14^th vaccine can be omitted (but not recommended to omit)
• In comparison of Rabies vaccine and COVID vaccine
  • Preference is given to Rabies vaccine.
  • Any other vaccine can be given after a 14 days gap.

Anti-Rabies Vaccine

• The different types of Anti Rabies Vaccines are
  • Nervous tissues Vaccines
  • Avian Embryo Vaccines
  • Primary cell culture Vaccines: Human Diploid Cell Vaccines- Currently used 
• Vaccines approved for ID use: Verorab, Rabipur, Abhayrab; these are commonly used.
• Rabies vaccine is a killed and Reconstituted vaccine.
• It has to be used within 6 hours.

Q. A 10 year old child with an unprovoked dog bite comes to you. He has suffered a deep wound. Appropriate action is:

1. Local treatment of wound for 15 minutes
2. Withhold vaccine and observe dog for 10 days
3. Give cell culture derived vaccine
4. Kill the dog and send brain for biopsy
5. Immediate suturing of the wound should be done 

1. a, d
2. a, b, e
3. a, c, d
4. a, c
5. a, c, e

Rabies in Dogs

• Dogs are the most important source of Urban rabies.
• Control
  • Dogs need to be vaccinated.
  • If in any community, 80% of the dog population is vaccinated, Rabies can be controlled. 
  • 80-90% of the dog population is accessible for vaccination
  • Dogs should receive primary immunisation at age of 3-4 months and booster doses should be given at regular intervals
• Rabies in dogs manifest in 2 forms:
  1. Furious rabies- the dog has got mad and it is biting everyone
  2. Dumb rabies- the dog has become completely silent

Q. An urban area has higher No. of rabies cases. Most cost effective and logical approach of controlling rabies is

1. Testing all dogs for rabies
2. Capacity building 
3. Removing stray dogs and vaccinating dog population 
4. Building cooperation among health workers

Types of Vaccines

1. BPL inactivated nervous tissue vaccine (single dose)
   • Dose
     • 5ml for dogs 
     • 3 ml for cats.
   • Revaccination advised after 6 months and subsequently every year.
2. Modified live virus vaccine
   • Dose is 
     • 3ml by single injection 
     • Booster dose every 3 years
   • Eliminate all the stray dogs and zone adults 80% of the dog population.

Other Methods Include

• Registering and licensing of all domestic dogs
• Restraint of dogs in public places 
• Immediate destruction of dogs and cats bitten by rabid animals.
• Quarantine for 6 months of imported dogs.
• Health education of people regarding care of dogs and prevention of rabies.

Q. In India, urban rabies is maintained by?

1. Dogs 
2. Cats
3. Rats
4. Mongoose

Q. All are features of rabies in man except?

1. Dead end infection
2. Aerosol transmission is quite common
3. Common age group 1-24 years
4. All animals are susceptible to rabies

Q. Rabies is not found in?

1. Lakshadweep islands
2. Rajasthan
3. Meghalaya
4. Orissa

Q. A classical cause of Rabies is characterised by all except?

1. Variable incubation period 
2. Short period of illness
3. Encephalomyelitis always present 
4. Fatal only some cases 

Q. A 10 year old child with an unprovoked dog bite comes to you. Appropriate action is?

1. Withhold vaccine and observe dog for 10sae a
2. Give cell culture derived vaccine
3. No further action is necessary 
4. Kill the dog and send brain for biopsy

Q. Pre-exposure prophylaxis for rabies is given on?

1. Days 0, 3, 7, 14, 28, 90
2. Days 0,3, 7, 28, 90
3. Days 0, 3
4. Days 0, 7, 28

And that is everything you need to know about Rabies for your PSM preparation. For more informative and interesting blog posts, download the PrepLadder App and keep following our blog!