Dog Bite

Puncture, laceration or crush injury from a canine bite, causing direct tissue trauma plus a high infection risk from oral flora inoculation; polymicrobial, including Pasteurella multocida, Staphylococcus, Streptococcus, anaerobes, and Capnocytophaga canimorsus (particularly severe in asplenic or immunocompromised patients). Also carries rabies risk in endemic areas, which is a critical consideration in management.

Classified by wound type (puncture: deep, narrow, high infection risk despite small external appearance; laceration; crush; avulsion) and by severity (minor superficial vs. severe: deep, crush, involving face/hands/genitals, joint/tendon/bone involvement, or in a high-risk patient).

• Puncture wounds, lacerations, crush injuries, tissue avulsion; commonly hands, face (especially children, given height relative to the dog), and lower limbs

• High infection risk features: deep puncture wounds (especially over joints; septic arthritis risk), hand wounds, wounds >8-12 hours old at presentation, immunocompromised host, crush component

• Signs of established infection: increasing pain, swelling and erythema beyond the wound margins, purulent discharge, lymphangitis, fever, regional lymphadenopathy; typically 24-72 hours post-bite if untreated

• Assess for deep structure involvement: tendon function distal to the wound, joint capsule penetration, neurovascular status, bone involvement (especially skull in young children with deep facial or scalp bites; intracranial penetration risk)

• Rabies exposure assessment: unprovoked attack, unknown or unvaccinated animal, endemic area, and type of contact (bite vs. lick on broken skin vs. scratch)

• Clinical wound assessment: depth, location, deep structure involvement
• X-ray: if bone or joint involvement is suspected, a retained tooth fragment is possible, or for a facial bite in a young child (skull penetration risk)
• Wound swab/culture: only if signs of established infection are present, not routinely for fresh wounds
• FBC/CRP if systemic infection signs

Differentials: cat bite or scratch (higher infection rate than dog bites due to the puncture mechanism and Pasteurella), other animal bites with region-specific rabies risk.

• Wound irrigation: copious saline or water irrigation; the single most important infection-prevention measure

• Wound closure: primary closure is generally AVOIDED for puncture wounds and high-risk bites (hand, high-risk sites, >8h old, immunocompromised); leave open or use delayed primary closure. Facial wounds are often closed primarily given cosmetic priority and good vascularity, with prophylactic antibiotics, after thorough irrigation and debridement

Prophylactic antibiotics; recommended for puncture wounds, hand/foot/face/genital bites, wounds requiring closure, immunocompromised patients, crush component, or joint/tendon proximity:

• Co-amoxiclav 625mg PO tds for 5-7 days (covers Pasteurella, anaerobes, staph/strep); first-line

• Penicillin-allergic: doxycycline + metronidazole, or clindamycin + ciprofloxacin

• Established infection: same agents, extended duration (7-14 days), consider IV therapy if systemic signs, urgent surgical review if joint, tendon sheath or deep space infection is suspected

Tetanus prophylaxis per immunization status.

Rabies risk assessment and post-exposure prophylaxis (PEP); critical in endemic areas:

• Wound care: immediate thorough washing with soap and water for 15 minutes significantly reduces viral load

• PEP per WHO risk categorization: Category I (touching/feeding; no PEP), Category II (minor scratches or abrasions without bleeding; vaccine only), Category III (transdermal bites or scratches, licks on broken skin or mucosa, or any contact with bats; vaccine + rabies immunoglobulin)

• Rabies vaccine: intramuscular regimen (days 0, 3, 7, 14, ±28) per WHO Essen or Zagreb schedule, or intradermal dose-sparing regimens where available

• Rabies immunoglobulin: infiltrated around and into the wound as far as anatomically feasible, remainder IM at a distant site; for Category III exposures, or Category II in the immunocompromised, given with the first vaccine dose

• If the biting animal is available for 10-day observation and remains healthy, PEP can be discontinued per WHO protocol; but do not delay starting PEP while awaiting the observation outcome in a high-risk exposure

Asplenic patients: heightened vigilance for Capnocytophaga sepsis, which can progress to fulminant sepsis and DIC; lower threshold for antibiotics and admission.

Referral: surgery or plastics for deep facial wounds, hand surgery for tendon or joint involvement, urgent surgical review for suspected septic arthritis or deep space infection.