Introduction to Rabies and Dog Bites

Rabies is an acute viral disease causing fatal encephalomyelitis that is practically $100\%$ fatal but highly preventable.
The virus is transmitted through the saliva of rabid animals via bites, scratches, or licks on broken skin and mucous membranes.
Bites by dogs are responsible for approximately $97\%$ of all human rabies cases in India.
In rabies-endemic countries, every animal bite must be suspected as a potentially rabid animal bite and managed as a medical emergency.

Classification of Animal Bite Exposures

The World Health Organization categorizes animal bite contacts into three distinct categories to guide the required post-exposure prophylaxis (PEP).

Category	Type of Contact	Recommended Post-Exposure Prophylaxis
Category I	Touching or feeding animals; licks on intact skin	None, provided a reliable case history is available
Category II	Nibbling of uncovered skin; minor scratches or abrasions without bleeding	Wound management and Anti-rabies vaccine
Category III	Single or multiple transdermal bites or scratches; licks on broken skin; contamination of mucous membrane with saliva	Wound management, Rabies immunoglobulin, and Anti-rabies vaccine

Post-exposure prophylaxis requires a simultaneous three-pronged approach depending on the specific category of exposure.

Physical removal of the virus: Prompt, gentle, and thorough washing of the wound with soap or detergent, followed by flushing with copious amounts of running water, is the most critical initial step.
Chemical inactivation: After thorough washing and drying, chemical viricidal agents such as povidone-iodine or alcohol must be applied to the wound.
Biological neutralization: For Category III exposures, Rabies Immunoglobulin (RIG) should be infiltrated deep into and around the wound.
Harmful practices to avoid: The wound should not be touched with bare hands, and irritants like soil, chilies, oil, turmeric, or lime should never be applied; if already applied, they must be washed off with soap or detergent.
Surgical precautions: Suturing of the bite wound should be avoided as much as therapeutically possible.
If suturing is surgically unavoidable, it must be delayed by a few hours after adequate wound cleansing and local RIG infiltration.
Only minimum loose sutures should be applied to arrest life-threatening bleeding.
Cauterization of the wound is contraindicated as it leaves bad scars and provides no additional benefit over soap and water washing.
Tetanus toxoid and antibiotic prophylaxis should be administered to prevent secondary bacterial sepsis.

RIG provides immediate Passive Immunity via ready-made anti-rabies antibodies before the child's own immune system can mount a response to the vaccine.
It is strictly indicated for all Category III exposures and for Category II exposures in immune-compromised individuals.
Equine Rabies Immunoglobulin (ERIG): Administered at a dose of $40 \text{ IU/kg}$ body weight.
Human Rabies Immunoglobulin (HRIG): Administered at a dose of $20 \text{ IU/kg}$ body weight.
Anatomical administration: As much of the calculated RIG dose as anatomically feasible must be infiltrated directly into the depth and around the margins of the wound(s).
If any RIG volume remains, it must be administered via deep intramuscular injection at a site distant from the vaccine injection site.
In small children with multiple or severe wounds, the calculated RIG volume can be diluted in sterile normal saline to assure sufficient volume to infiltrate all wound sites.
RIG must never be administered in the same syringe or at the exact same anatomical site as the anti-rabies vaccine.
RIG is administered only once, preferably within 24 hours (Day 0) and up to a maximum of the 7th day following the first dose of the anti-rabies vaccine.

Active immunization is achieved using safe and potent Cell Culture Vaccines (CCVs) or Purified Duck Embryo Vaccine (PDEV).
All pediatric bite victims of Category II and III exposures, regardless of age and body weight, require the identical number of injections and the same dose per injection as adults.
Intramuscular (IM) Regimen (Essen Schedule): A five-dose schedule ($1-1-1-1-1$) administered on Days 0, 3, 7, 14, and 28.
For infants and young children, the antero-lateral aspect of the thigh is the strongly preferred site for IM injection.
The deltoid region is used for older children; the gluteal region is strictly contraindicated because local fat retards antigen absorption and impairs the immune response.
Intradermal (ID) Regimen (Updated Thai Red Cross Schedule): This involves the injection of $0.1 \text{ ml}$ of reconstituted vaccine per ID site, on two sites per visit (one on each deltoid area) on Days 0, 3, 7, and 28 (a $2-2-2-0-2$ schedule).

A 10-day observation period is clinically valid exclusively for dogs and cats.
If the biting dog remains perfectly healthy throughout the entire 10-day observation period, the PEP schedule can be clinically modified.
For the IM regimen, the post-exposure prophylaxis can be converted to pre-exposure prophylaxis by skipping the Day 14 vaccine dose and administering it on Day 28.
If the ID administration route is being utilized, the complete course of vaccination must be fully administered irrespective of the biting animal's health status.
A provoked bite or a history of prior animal vaccination does not guarantee that the animal is free of rabies; hence, PEP should be initiated immediately regardless of these factors.