Human & Animal Bites

Topic Overview

Summary

Mammalian bite wounds present a significant infectious disease challenge due to polymicrobial oral flora, with infection rates varying from 5% (dog bites) to 50% (cat bites). The unique anatomy of bite wounds—particularly deep puncture injuries and "fight bites" over the metacarpophalangeal (MCP) joint—creates ideal conditions for serious complications including septic arthritis, tenosynovitis, and osteomyelitis. Certain organisms pose life-threatening risks: Capnocytophaga canimorsus causes fulminant sepsis in asplenic patients, while Pasteurella multocida from cat bites produces rapid-onset cellulitis within 24 hours. Optimal management requires meticulous wound care, appropriate antibiotic prophylaxis (co-amoxiclav first-line), tetanus assessment, and recognition of surgical emergencies—particularly fight bite injuries which mandate exploration regardless of wound appearance.

Key Facts

• Dog bites: 80-90% of mammalian bites; Pasteurella spp., Capnocytophaga canimorsus (fatal sepsis in asplenic/immunocompromised)
• Cat bites: Deep puncture wounds, 30-50% infection rate; Pasteurella multocida (75% of infections); high risk tenosynovitis
• Human bites: Eikenella corrodens, oral streptococci, anaerobes; "fight bite" = MCP joint penetration = surgical emergency
• Antibiotics: Co-amoxiclav 625mg TDS for prophylaxis/treatment; covers Pasteurella, streptococci, anaerobes
• Wound closure: Primary closure contraindicated in most bites; delayed primary closure at 3-5 days if clean
• Fight bite: Clenched fist injury over MCP requires surgical washout; up to 75% complication rate without exploration

Clinical Pearls

Cat bites appear deceptively minor but have 30-50% infection rates—deep puncture mechanism inoculates Pasteurella multocida into tendons and joint spaces. ALWAYS prescribe prophylactic antibiotics for ALL cat bites.

"Fight bite" diagnosis: examine hand in clenched fist position to reveal true depth of penetration. Even small wounds over MCP joints can communicate with joint space/extensor tendon—surgical exploration is mandatory.

Capnocytophaga canimorsus sepsis in asplenic/immunocompromised patients: fulminant presentation with purpura, DIC, gangrene, and mortality up to 30%. Aggressive empirical antibiotics essential.

Pasteurella infection presents rapidly (12-24 hours) with intense cellulitis—if patient presents early with dog/cat bite, anticipate this pattern and ensure antibiotic compliance.

CRITICAL ERROR: Prescribing flucloxacillin or clindamycin alone for bite wounds. Both are INEFFECTIVE against Pasteurella and Eikenella—the hallmark pathogens of animal and human bites. Co-amoxiclav is GOLD STANDARD.

Cat bite to hand = SURGICAL EMERGENCY POTENTIAL: 57% require hospitalization, 38% require surgery (drainage, washout). Threshold for admission and IV antibiotics must be LOW. Don't wait for infection to declare itself.

Fight bite over MCP = ALWAYS EXPLORE SURGICALLY: 100% infection rate if delayed > 48h without washout. Small 3mm skin wound may hide 15mm deep tendon/joint penetration. Radiograph mandatory (tooth fragments, fracture).

Human bite microbiology is ANAEROBE-HEAVY (50-80%): Metronidazole or anaerobic coverage mandatory. Clindamycin WON'T work alone (misses Eikenella). Use co-amoxiclav or doxycycline + metronidazole.

Wound closure increases infection risk 2-4×: Default to delayed closure (3-5 days) or secondary intention. Exception: facial wounds (low infection risk, cosmetic priority) but only with copious irrigation + antibiotics.

Tetanus prophylaxis is NON-NEGOTIABLE: All bites are tetanus-prone. If patient has incomplete immunization + bite wound, give Td booster + TIG (250 IU IM). Tetanus kills even in modern ICUs.

Rabies is 100% fatal once symptomatic: If bitten abroad or by animal of uncertain origin, immediate wound irrigation (15 minutes soap/water) reduces viral load 90%. Contact Public Health immediately for PEP decision—don't delay.

Asplenic patient + dog bite = PROPHYLACTIC ANTIBIOTICS MANDATORY: Capnocytophaga risk is 200-400× higher. Low threshold for admission/observation. Educate asplenic patients to seek IMMEDIATE care for ANY bite.

Why This Matters Clinically

Bite wounds account for approximately 1% of emergency department attendances (250,000-300,000 cases annually in the UK), yet their management is frequently suboptimal. Delayed treatment or inadequate antibiotic prophylaxis results in preventable complications: septic arthritis requiring multiple surgeries, chronic osteomyelitis, permanent functional impairment of the hand, and rare but fatal septicaemic syndromes. Recognition that cat bites and fight bites are high-risk injuries—regardless of benign appearance—is critical to preventing devastating outcomes.

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Visual Summary

Bite Wound Management Algorithm

MAMMALIAN BITE PRESENTATION
          ↓
    IMMEDIATE ACTIONS
    • Irrigation: 250-500ml saline
    • Wound exploration
    • Neurovascular/tendon exam
    • X-ray (hand bites, fight bites)
          ↓
  ┌─────────────────────┐
  │ INFECTION PRESENT?  │
  └─────────────────────┘
     YES ↓         ↓ NO
         ↓         └→ RISK STRATIFICATION
         ↓              ↓
    TREATMENT      HIGH RISK?
    Path           • ALL cat bites
         ↓         • ALL human bites (skin breach)
    Severe?       • Hand/wrist/foot/face/genitals
    YES ↓  ↓ NO   • Deep puncture
       ↓   └→ Oral  • Immunocompromised
       ↓      Co-amoxiclav  • Delay greater than 12h
       ↓      625mg TDS      ↓
       ↓      7-10 days   YES ↓  ↓ NO
       ↓                     ↓   └→ Wound care
    IV Antibiotics          ↓      Observe
    Co-amoxiclav 1.2g TDS   ↓      Review 48h
    Until improved          ↓
    Then switch oral     PROPHYLAXIS
    Total 10-14 days     Co-amoxiclav 625mg TDS
         ↓               5-7 days
    SURGICAL?               ↓
    • Fight bite        WOUND CLOSURE?
    • Kanavel's signs   DEFAULT: Leave open
    • Septic arthritis  EXCEPTIONS:
    • Deep space        • Facial wounds
    • NF suspected      • Selected low-risk
         ↓              With irrigation
    Urgent theatre      + Antibiotics
    Exploration            ↓
    Washout            FOLLOW-UP
    IV antibiotics     • 24-48h review
                       • Infection monitoring
                       • Tetanus status
                       • Rabies risk (if abroad)

Additional visual assets to be added:

• Hand anatomy: MCP joint, extensor apparatus, flexor tendons
• "Fight bite" mechanism: wound position in fist vs. extended
• Kanavel's signs diagram for flexor tendon sheath infection
• Pasteurella multocida Gram stain and culture characteristics
• Polymicrobial culture results from bite wounds

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Epidemiology

Incidence & Prevalence

Global Burden:

• Mammalian bites: 2-5 million/year in United States [7,32]
• Emergency department attendances: ~1% of all ED visits for bite wounds [29,32]
• UK data: approximately 250,000-300,000 bite presentations annually [11]

Distribution by Animal:

• Dog bites: 60-90% of all mammalian bites (most common) [6,7,32]
• Cat bites: 5-20% of mammalian bites [6,8]
• Human bites: 2-3% of bite presentations (likely underreported due to assault context) [12,13]
• Other mammals: Rats, horses, pigs, monkeys (less than 5% combined) [29]

Demographics

Dog Bites:

• Peak incidence: Children aged less than 10 years (highest incidence); male predominance (60-65% male) [7,11,43,44]
• Anatomical distribution: Children—head/neck (50%), face (25%); Adults—upper extremity (50-56%), lower extremity (30%) [7,11,44]
• Most dogs known to victim (75-80%); owned by victim's family (20-30%) [11]
• Geographic/temporal patterns: More common in rural settings, private residences, summer months [43]

Cat Bites:

• Peak incidence: Adult women (65-75% female); bimodal peaks in middle-aged adults (45-55 years) and elderly (≥80 years) [8,35,43]
• Anatomical distribution: Upper extremity (85%), especially hands/fingers (70%) [8,9,35,39,44]
• Predominantly domestic cats (> 95%) [8]
• Bacteria isolated at initial ED presentation: 21.5% of cat bites vs. 3% of dog bites [43]

Human Bites:

• Peak incidence: Young adult males aged 18-35 years [12,13]
• Male predominance (70-80% male) [12,13]
• Alcohol involvement: 40-50% of cases [12]
• Anatomical distribution: Hands (70%), especially MCP region ("fight bite"); upper extremity (85%) [12,13,14]
• Occlusional bites (deliberate): Children in care/abuse contexts; sexual assault; psychiatric disorders [29]

Infection Rates by Animal Type

Risk Factors for Infection:

• Location: Hand (20-30%), foot (15-20%) > other sites (3-10%) [6,19,25]
• Delay to treatment: > 12 hours significantly increases risk [5,17,32]
• Host factors: Diabetes, immunosuppression, liver disease, asplenia, peripheral vascular disease [6,15,29]
• Wound characteristics: Deep puncture > laceration; crush injury; devitalised tissue [6,22,24]
• Animal: Cat > human > dog [6,7,8]

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Pathophysiology

Mechanisms of Tissue Injury

Dog Bites:

• Powerful jaw muscles (150-450 psi bite force in large breeds)
• Crush injury: Tissue devitalisation, contusion, vascular compromise
• Tear/avulsion: Shearing forces cause tissue loss, scalp/facial injuries in children
• Deep structures at risk: Muscle, tendon, bone, neurovascular bundles
• Crush mechanism → devitalised tissue → bacterial proliferation

Cat Bites:

• Sharp, fine canine teeth (2-3mm diameter)
• Deep puncture wounds: Penetration of joint capsules, tendon sheaths, bone
• Minimal surface trauma but deep inoculation
• Hand anatomy vulnerability: Thin subcutaneous tissue → direct tendon/joint penetration
• Sealed wound traps bacteria in deep structures
• High pressure inoculation → tenosynovitis, septic arthritis

Human Bites:

Occlusional Bites:

• Closure of teeth on tissue (fingers, ears, nose, genitals)
• Tissue compression and tearing
• Variable depth

Clenched Fist Injuries ("Fight Bite"):

• Fist strikes opponent's teeth
• Tooth penetrates skin over MCP joint
• Critical mechanism: Wound occurs with MCP flexed/finger tendons tight
• When hand opens: Wound migrates proximally relative to deeper structures
• Bacteria/foreign material (tooth fragments, oral debris) sealed within joint/tendon sheath
• Small external wound belies deep penetration

Microbiology: A Polymicrobial Ecosystem

Bite wounds are typically polymicrobial (average 5 bacterial species per wound). Oral flora varies by animal but consistently includes aerobes, facultative anaerobes, and strict anaerobes.

Comparative Microbiology by Animal Type

Key Distinctions:

• ⭐ = Hallmark/most prevalent organism for that animal type
• Dog bites: Pasteurella canis + Capnocytophaga (asplenic risk)
• Cat bites: Pasteurella multocida dominance (75-80%)—rapid onset, deep penetration
• Human bites: Streptococci + anaerobes + Eikenella (clindamycin-resistant)

Dog Bite Microbiology

Predominant Organisms (Prevalence in Infected Wounds):

• Pasteurella species (50-75%): P. canis (most common in dogs), P. multocida, P. stomatis, P. dagmatis
  • Gram-negative coccobacilli; isolated from 50% of dog mouths
  • Rapid onset infection (24-48 hours)
  • Beta-lactamase production rare (3-5%)
• Capnocytophaga canimorsus (20-30% of dog oral flora; 5-10% of infected bites)
  • Fastidious Gram-negative rod; requires CO₂ for growth
  • Commensal in canine gingiva
  • Causes fulminant sepsis in asplenic/immunocompromised (incubation 1-8 days)
  • Mortality 25-31% in septic presentations
• Streptococcus spp. (30-50%): S. canis (dog-specific), S. pyogenes, viridans group
• Staphylococcus spp. (20-40%): S. aureus (including MRSA 3-8%), S. intermedius (dog commensal), coagulase-negative staphylococci
• Anaerobes (40-70%): Fusobacterium spp., Bacteroides spp., Prevotella spp., Porphyromonas spp., Peptostreptococcus spp.
• Other: Neisseria spp. (10-15%), Moraxella spp., Corynebacterium spp., Bergeyella zoohelcum

Capnocytophaga canimorsus Pathogenesis:

• Bypasses complement-mediated killing (polysaccharide capsule with sialic acid residues)
• Particularly virulent in asplenic patients (spleen's role in clearing encapsulated organisms)
• Risk factors: Asplenia (RR 200-400×), alcohol use disorder (RR 5-10×), cirrhosis, immunosuppression
• Presents with rapid-onset sepsis (median 3 days; range 1-8 days)
• Clinical triad: Fever/septic shock + DIC/purpura fulminans + symmetric peripheral gangrene
• Complications: Multi-organ failure, acute kidney injury, rhabdomyolysis, meningitis (8-10%), endocarditis (5%)
• Mortality 25-31% even with treatment in high-risk hosts; 8-10% in immunocompetent
• Slow-growing organism (5-7 days); empirical therapy critical—cannot wait for cultures

Cat Bite Microbiology

Predominant Organisms (Prevalence in Infected Wounds):

• Pasteurella multocida (75-80%): DOMINANT pathogen in cat bites
  • Present in 70-90% of healthy cat oral cavities
  • Facultative anaerobic Gram-negative coccobacillus
  • "Multiple subspecies: P. multocida subsp. multocida (most common), P. multocida subsp. septica"
  • "Short incubation: 12-24 hours (median 16 hours)—HALLMARK of cat bite infection"
  • Produces endotoxin, dermonecrotic toxin, hyaluronidase (tissue penetration)
  • "Preferentially invades deeper structures: tendons, joints, bone"
• Pasteurella species (15-20%): P. canis, P. stomatis, P. dagmatis
• Streptococcus spp. (30-40%): Viridans group, S. pyogenes, S. anginosus group
• Staphylococcus spp. (20-30%): S. aureus (often secondary infection after 48-72h), coagulase-negative staphylococci
• Bartonella henselae (30-40% of cat oral flora): Cat scratch disease pathogen; less common in acute bite infections
• Anaerobes (30-50%): Fusobacterium, Prevotella, Porphyromonas, Peptostreptococcus
• Other: Moraxella spp., Neisseria spp.

Pasteurella multocida Pathogenesis:

• Facultative anaerobic Gram-negative coccobacillus
• Short incubation: 12-24 hours (median 16 hours; range 3-48 hours)—HALLMARK rapid onset
• Produces rapid, intense inflammatory response (intense cellulitis within hours)
• Virulence factors:
  • Lipopolysaccharide endotoxin (systemic inflammation)
  • Dermonecrotic toxin (cytotoxic to fibroblasts, epithelial cells)
  • Hyaluronidase (tissue penetration and spread)
  • Capsular polysaccharide (anti-phagocytic)
  • Neuraminidase (tissue invasion)
• Preferentially invades deeper structures via puncture mechanism:
  • Flexor tenosynovitis (10-15% of cat hand bites)
  • Septic arthritis (5-8%)
  • Osteomyelitis (3-5%)
• Complications: Bacteremia (1-3%), endocarditis (rare), meningitis (rare, often immunocompromised)
• Antimicrobial susceptibility: Penicillin-susceptible (> 95%); naturally resistant to clindamycin, first-generation cephalosporins (cephalexin)

Human Bite Microbiology

Predominant Organisms (Prevalence in Infected Wounds):

• Eikenella corrodens (25-30%): MARKER organism for human bites
  • Facultative anaerobic Gram-negative rod
  • Commensal in human oral cavity (40-70% carriage)
  • Slow-growing, fastidious (requires 5-10% CO₂, 48-72h culture)
  • Forms biofilms on damaged tissue and foreign material
  • Associated with abscess formation, osteomyelitis (8-12% of human bite osteomyelitis)
  • "Naturally resistant to: Clindamycin, metronidazole, aminoglycosides, vancomycin"
  • "Susceptible to: Penicillin, amoxicillin-clavulanate, ceftriaxone, fluoroquinolones"
• Streptococcus spp. (50-70%): MOST COMMON isolate overall
  • "S. anginosus group (S. milleri, S. constellatus, S. intermedius): 30-40%—abscess-forming"
  • "Viridans group streptococci: 40-60%"
  • "S. pyogenes (Group A): 5-10%"
  • Beta-hemolytic streptococci
• Staphylococcus spp. (30-50%):
  • "S. aureus: 20-40% (including MRSA 5-15% in some regions)"
  • "S. epidermidis and coagulase-negative staphylococci: 10-20%"
• Anaerobes (50-80% of infections): HIGHLY PREVALENT—polymicrobial
  • "Prevotella spp.: 20-40% (oral anaerobic Gram-negative rods)"
  • "Fusobacterium nucleatum: 20-30%"
  • "Peptostreptococcus spp.: 15-25% (anaerobic Gram-positive cocci)"
  • "Veillonella spp.: 10-15%"
  • "Porphyromonas spp., Bacteroides spp. (non-fragilis): 10-20%"
• Other aerobes: Haemophilus spp. (10-15%), Corynebacterium spp., Actinomyces spp.

Polymicrobial Nature:

• Human bite wounds average 4-7 bacterial species per wound
• Aerobic + anaerobic combination in > 80% of infections
• Synergy between organisms increases virulence

Eikenella corrodens Characteristics:

• Slow-growing, difficult to culture (requires 5-10% CO₂; 48-72h incubation)
• Often missed without specific microbiology notification ("human bite" on request form alerts lab)
• Produces characteristic "bleach-like" odor on culture plates
• Forms biofilms on damaged tissue/foreign material (problematic in joint/bone infections)
• Associated with indolent, chronic infections (abscesses, osteomyelitis requiring prolonged therapy)
• CRITICAL antimicrobial resistance pattern:
  • "Resistant to: Clindamycin (intrinsic), metronidazole (intrinsic), aminoglycosides, vancomycin, first-generation cephalosporins"
  • "Susceptible to: Penicillin (> 95%), amoxicillin-clavulanate, ampicillin-sulbactam, ceftriaxone, cefotaxime, fluoroquinolones (ciprofloxacin, levofloxacin), doxycycline"
• Clinical significance: Clindamycin or metronidazole monotherapy will FAIL—requires beta-lactam or fluoroquinolone

Blood-borne Virus Transmission:

• Hepatitis B: Documented transmission risk (especially with visible blood in saliva)
• Hepatitis C: Rare; theoretical risk
• HIV: Extremely rare; no definitive cases from bites alone (saliva has inhibitory factors)

Anatomical Considerations: The Hand

The hand's unique anatomy makes bites particularly hazardous:

Tissue Compartments:

• Minimal subcutaneous fat → tendon sheaths, joints lie immediately deep to skin
• 9 flexor tendon sheaths: Enclosed synovial spaces susceptible to infection
• MCP, PIP, DIP joints: Minimal soft tissue coverage
• Deep palmar spaces: Thenar, hypothenar, mid-palmar compartments

Fight Bite Mechanism:

• MCP joint in flexion during punch
• Extensor tendon/extensor hood/joint capsule vulnerable to penetration
• When hand opens: Wound on skin moves ~1-2cm proximal to extensor apparatus injury
• Small 3-4mm skin wound may represent 10-15mm deep penetration to bone
• Bacteria/tooth fragments trapped beneath extensor hood or in joint

Infectious Complications:

• Flexor tenosynovitis: Pyogenic infection of flexor tendon sheaths (Kanavel's signs)
• Septic arthritis: Direct bacterial inoculation into MCP/IP joints
• Deep space infection: Thenar, hypothenar, mid-palmar abscesses
• Osteomyelitis: Direct bacterial access to bone (fight bite → metacarpal head)

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Clinical Presentation

Fresh Wound (Pre-Infection)

History:

• Time elapsed since bite
• Animal type (dog breed, cat domestic/feral, human bite context)
• Provoked vs. unprovoked attack
• Rabies risk assessment: Animal behaviour, geographic location
• Patient factors: Diabetes, immunosuppression, liver disease, asplenia, prosthetic joints
• Concealed history: Assault (fight bite), abuse (child/vulnerable adult)

Wound Characteristics:

• Dog bites: Lacerations, punctures, crush injuries, tissue loss/avulsion
• Cat bites: Small puncture wounds (1-3mm), often multiple, minimal bleeding
• Fight bites: Small laceration/puncture over MCP joint (typically 3rd or 4th MCP)

High-Risk Features on Initial Assessment:

• Location: Hand, wrist, foot, face, genitals, scalp (infants)
• Depth: Penetration to tendon, joint, bone
• Devitalised tissue, crush injury
• Delay > 12 hours
• Immunocompromised host

Established Infection (12-72 Hours)

Early Presentation (Pasteurella Infection: 12-24h):

• Rapid onset intense cellulitis
• Severe pain, swelling, erythema
• Purulent discharge
• Advancing lymphangitis
• Low-grade fever
• Typical of cat bites and some dog bites

Delayed Presentation (24-72h):

• Progressive cellulitis/abscess
• Systemic symptoms: Fever, malaise
• Lymphadenopathy (regional nodes)
• Spreading erythema

Late Complications (> 72h):

• Deep space infection
• Tenosynovitis
• Septic arthritis
• Osteomyelitis
• Necrotising soft tissue infection (rare)

Specific Syndromes

Flexor Tenosynovitis (Kanavel's Signs)

Classic tetrad (all four signs = high specificity):

1. Fusiform swelling of digit (sausage-shaped)
2. Flexed posture of digit at rest
3. Tenderness along flexor tendon sheath (entire length, not just wound)
4. Pain on passive extension (most sensitive sign)

Urgency: Surgical emergency—requires washout within 24 hours to prevent tendon necrosis.

Septic Arthritis (MCP/IP Joints)

• Intense joint pain
• Swelling, effusion
• Warmth, erythema
• Restricted/absent range of motion
• Inability to bear weight through hand
• Systemic sepsis may develop

Urgency: Surgical emergency—requires washout/drainage.

Capnocytophaga canimorsus Sepsis

• Asplenic, liver disease, alcohol excess, immunosuppression
• Rapid-onset sepsis 2-7 days post-bite
• Fever, rigors, hypotension
• Purpura fulminans (DIC)
• Symmetric peripheral gangrene (digits, nose, ears)
• Meningitis, endocarditis (rare)
• Mortality 25-30% despite treatment

Red Flags — Immediate Action Required

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Clinical Examination

Primary Survey (Systemically Unwell Patients)

• Airway, breathing, circulation
• Sepsis screening: Temp, HR, BP, RR, GCS, lactate
• Focused examination of bite wound
• Empirical antibiotics FIRST in septic patient

Wound Assessment

Structured Examination:

1. Site: Anatomical location; document precisely (e.g., "dorsum 3rd MCP joint")
2. Size: Measure wound dimensions (length, width, depth if visible)
3. Depth: Superficial (dermis), deep (fascia/tendon/joint/bone)
4. Tissue viability: Devitalisation, crush injury, ischaemia
5. Contamination: Visible foreign material (tooth fragments, debris)
6. Signs of infection: Erythema, warmth, purulent discharge, crepitus (gas)

Wound Probing (Controversial):

• May be performed gently to assess depth
• Fight bites: Probe ONLY with hand in clenched fist position (mimics injury mechanism)
• Avoid aggressive probing (iatrogenic injury)

Hand Examination (Mandatory for All Hand Bites)

Neurovascular Assessment:

• Radial/ulnar pulses: Vascular injury
• Capillary refill: Each digit
• Sensation: Two-point discrimination (radial/ulnar digital nerves)
• Allen's test: If vascular injury suspected

Tendon Integrity:

• Flexor digitorum profundus (FDP): Isolated DIP flexion
• Flexor digitorum superficialis (FDS): Isolated PIP flexion (hold other fingers extended)
• Extensor digitorum communis: MCP/IP extension against resistance
• Flexor pollicis longus (FPL): Thumb IP flexion
• Extensor pollicis longus/brevis (EPL/EPB): Thumb extension

Range of Motion:

• Active ROM: Full flexion/extension of each digit
• Passive ROM: Assess for tendon sheath infection (pain on passive stretch)

Special Tests:

• Kanavel's signs: See above (flexor tenosynovitis)
• Joint stress tests: Collateral ligament integrity (if laceration near joint)

Fight Bite-Specific Examination:

• Examine with hand in clenched fist
• Wound appearance changes with hand position
• Look for underlying extensor tendon laceration
• Palpate for tooth fragments (crepitus)

Documentation

Record comprehensively (medico-legal):

• Mechanism and time of bite
• Animal type and vaccination status (if known)
• Detailed wound description (site, size, depth)
• Neurovascular status
• Tendon integrity
• Signs of infection
• Tetanus status
• Photographs (if possible and consent obtained)

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Investigations

Point-of-Care/Bedside

Imaging

Plain Radiographs (X-ray)

Indications:

• All hand bites
• All fight bites (mandatory)
• Deep wounds
• Suspicion of fracture
• Suspicion of foreign body (tooth fragment)
• Signs of established infection

Views:

• AP, lateral, oblique (minimum two views)

Findings:

• Foreign bodies: Tooth fragments (radiopaque), glass
• Fractures: Metacarpals, phalanges (punch injury)
• Gas: Soft tissue gas (anaerobic infection; necrotising fasciitis)
• Periosteal reaction: Osteomyelitis (late finding, > 10-14 days)
• Joint space narrowing/erosion: Septic arthritis (late finding)

Advanced Imaging

Laboratory Investigations

Microbiology

Important: Notify microbiology "bite wound" → alerts lab to incubate for fastidious organisms (Capnocytophaga, Eikenella, Pasteurella).

Haematology & Biochemistry

Blood-borne Virus Screening (Human Bites)

Baseline (Victim):

• Hepatitis B surface antibody (if immunised, check protective level)
• Hepatitis C antibody
• HIV antibody/Ag (if consented)

Source (Assailant) Testing:

• Ideally test assailant for HBV, HCV, HIV (requires consent or court order)

Follow-up:

• Repeat serology at 3 months (HBV, HCV) and 6 months (HIV) if high-risk exposure

Tetanus and Rabies Assessment

Tetanus Risk Assessment:

Definition of Tetanus-Prone Wound:

• Puncture wounds (especially if > 6mm deep)
• Wounds containing foreign bodies
• Wounds with devitalised/necrotic tissue
• Compound fractures
• Wounds contaminated with soil, manure, or saliva
• Delay > 6 hours from injury to medical treatment
• All mammalian bites are considered tetanus-prone

UK Tetanus Immunisation Schedule:

• Primary course: 3 doses (2, 3, 4 months)
• Boosters: Preschool (3 years 4 months), school-leaving (13-18 years)
• Total: 5 doses provides lifelong immunity (no further boosters required)
• Post-2006: Routine schedule provides 5 doses by age 18 years

Tetanus Prophylaxis Protocol

Tetanus Vaccine Formulations:

• Td vaccine: Tetanus + low-dose diphtheria (adult formulation)
  • "Dose: 0.5 mL IM (deltoid)"
  • Preferred for adults and children > 10 years
• Tdap vaccine: Tetanus + diphtheria + acellular pertussis
  • Consider if pertussis booster also due
  • Preferred in pregnancy (protect infant via maternal antibodies)

Tetanus Immunoglobulin (TIG):

• Indications:
  • Tetanus-prone wound (bite) + incomplete/unknown immunisation status
  • High-risk wounds (heavy contamination, > 24h delay, extensive devitalised tissue)
  • Immunocompromised patients (may not mount vaccine response)
• Dose: 250 IU IM (single dose)
  • 500 IU if heavy contamination or delay > 24 hours
• Administration:
  • Separate anatomical site from vaccine (e.g., vaccine in left deltoid, TIG in right deltoid or thigh)
  • Use different syringe and needle
• Timing: Ideally within 24 hours; effective up to 72 hours post-injury
• Formulations:
  • "Human TIG (HTIG): Preferred (no allergy risk)"
  • "Equine TIG: If HTIG unavailable (requires test dose; risk anaphylaxis)"

Special Considerations:

• Pregnancy: Td and TIG safe in all trimesters
• HIV/Immunosuppression: Complete 5-dose schedule; TIG for tetanus-prone wounds (may not respond adequately to vaccine alone)
• Older adults: If uncertain immunisation history, treat as unimmunised (many born pre-1961 may lack full course)

Tetanus Disease (If Prophylaxis Fails/Not Given):

• Incubation: 3-21 days (median 7 days)—shorter in heavily contaminated wounds
• Mortality: 10-20% even with ICU treatment
• PREVENT BY ENSURING ADEQUATE PROPHYLAXIS

Rabies Risk Assessment:

• UK domestic animals: ZERO rabies risk (UK officially rabies-free since 1902; last terrestrial case 1902, last bat case 2002)
• Imported animals: Risk if arrived in UK less than 6 months ago OR unclear vaccination/quarantine history
• Bites abroad: HIGH RISK in endemic countries (see below)
• High-risk countries: Asia (India, China, Thailand, Philippines, Vietnam), Africa (sub-Saharan), South America (Brazil, Peru), Middle East
• Animal behavioural indicators of rabies:
  • Unprovoked aggression
  • Altered behaviour (nocturnal animals active during day; wild animals approaching humans)
  • Hypersalivation ("foaming at mouth")
  • Paralysis, ataxia
  • Hydrophobia (fear of water—late sign)
  • Death typically within 7-10 days of symptom onset (in animal)

Rabies Post-Exposure Prophylaxis (PEP) Indications:

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Classification & Risk Stratification

Classification by Animal

Risk Stratification for Antibiotic Prophylaxis

High Risk (Prophylaxis ALWAYS Indicated):

• ALL cat bites (regardless of site/depth)
• ALL human bites with skin breach
• Bites to hand, wrist, foot, face, genitals, scalp
• Deep puncture wounds (any animal)
• Crush injury with devitalised tissue
• Immunocompromised host (diabetes, cirrhosis, asplenia, immunosuppression)
• Prosthetic joints or vascular grafts
• Delayed presentation (> 12 hours)

Moderate Risk (Consider Prophylaxis):

• Dog bites to extremities (not hand/foot)
• Superficial wounds

Low Risk (Prophylaxis Usually NOT Required):

• Very superficial abrasions without skin breach
• Immediate presentation, healthy patient, superficial laceration on trunk/proximal limb
• Wound already cleaned/irrigated extensively

Fight Bite Classification

Modified Chadaev Classification:

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Management

Immediate Wound Care (Critical First Step)

All bite wounds require meticulous wound care:

1. Analgesia: Ensure adequate pain control for wound exploration/irrigation

2. Irrigation (Single Most Important Intervention):

   • High-volume lavage: Minimum 250-500ml normal saline (up to 1-2L for larger/contaminated wounds)
   • Use 20-60ml syringe with 18-19G needle/catheter for high-pressure irrigation
   • Direct jet into wound depths
   • Removes bacterial load, debris, devitalised tissue
   • Tap water equally effective as sterile saline for low-risk wounds

3. Exploration:

   • Examine wound under good lighting
   • Extend wound if necessary to visualise deep structures
   • Identify tendon, joint capsule, bone involvement
   • Remove visible foreign material (tooth fragments, debris)

4. Debridement:

   • Excise devitalised, non-viable tissue (necrotic, crushed)
   • Conservative debridement (preserve viable tissue, especially in hand/face)
   • Do NOT excise wound edges routinely

5. Wound Closure:

PRIMARY CLOSURE — Generally CONTRAINDICATED in Bite Wounds

Rationale for Avoiding Primary Closure:

• High bacterial inoculum (10⁶-10⁹ organisms in oral cavity)
• Polymicrobial contamination (average 5 species per wound)
• Deep puncture mechanism (cat bites) traps bacteria
• Crush injury with devitalised tissue (dog bites)
• Evidence: Primary closure increases infection risk 2-4× compared to delayed closure

EXCEPTIONS—Consider Primary Closure (With Caution):

1. Facial Wounds (Cosmetic Priority + Low Infection Risk)

• Rationale:
  • Excellent blood supply → enhanced bacterial clearance
  • Lower infection rate (3-5% vs. 10-20% elsewhere)
  • Cosmetic importance (visible scarring)
• Criteria for closure:
  • less than 12 hours old (ideally less than 6 hours)
  • Thorough irrigation (≥500mL)
  • No devitalised tissue
  • Prophylactic antibiotics mandatory
  • Close follow-up (24-48h)
• Technique:
  • Loose approximation (avoid tension)
  • Consider subcutaneous sutures only (leave skin edges approximated but not closed)
  • Absorbable sutures preferred

2. Large, Gaping Wounds Requiring Hemostasis

• Scalp lacerations with brisk bleeding
• Wounds > 5cm where delayed closure impractical
• Consider loose approximation rather than tight closure

3. Low-Risk Dog Bites (Selective)

• Criteria (ALL must be met):
  • Trunk or proximal limb (NOT hand, foot, face)
  • Laceration (not puncture)
  • less than 8 hours old
  • No crush injury or devitalised tissue
  • Healthy, immunocompetent patient
  • Extensive irrigation performed (≥500mL high-pressure lavage)
  • Prophylactic antibiotics given
• Technique: Loose closure; avoid tight sutures

DELAYED PRIMARY CLOSURE (Preferred for Most Bites):

• Protocol:
  1. Leave wound open initially (after irrigation and débridement)
  2. Pack loosely with saline-soaked gauze
  3. Daily dressing changes
  4. Re-assess at 3-5 days
  5. Close if clean, no signs of infection (sutures, Steri-Strips, or tissue adhesive)
• Advantages:
  • Allows wound to declare infection
  • Reduces infection risk
  • Better cosmetic outcomes than secondary intention
• Evidence:
  • "Infection rate with delayed closure: 5-8%"
  • "Infection rate with immediate closure: 15-25%"
  • Cosmetic outcomes similar or superior to primary closure

SECONDARY INTENTION (Healing by Granulation):

• Indications:
  • Small puncture wounds (cat bites)—DO NOT CLOSE
  • Infected wounds
  • Heavily contaminated wounds
  • Hand wounds after surgical washout (fight bites)
  • Patient preference
  • Delayed presentation (> 24 hours)
• Protocol:
  • Pack wound with non-adherent dressing
  • Daily dressing changes initially
  • Transition to less frequent changes as granulation progresses
  • "Healing time: 2-6 weeks (size-dependent)"
• Outcomes: Acceptable cosmetic results for small wounds (less than 2cm)

Wound Closure Evidence Base:

• Paschos et al. (2014): Primary closure of hand bite wounds associated with 3.2× increased infection risk (OR 3.2, 95% CI 1.4-7.3)
• Dire et al. (1992): No increased infection with primary closure of selected low-risk dog bites (facial wounds, less than 8h old, thorough irrigation)
• NICE/IDSA guidelines: Delayed closure preferred; primary closure only for facial wounds or low-risk dog bites with extensive irrigation

Antibiotic Therapy

Prophylaxis (Non-Infected Wounds)

Indications: See Risk Stratification above.

First-Line: Co-amoxiclav (Amoxicillin-Clavulanate) ✅ GOLD STANDARD

Dose:

• Adults: 625mg (500mg amoxicillin + 125mg clavulanate) PO TDS
  • "Alternative high-dose: 1g/200mg (875mg/125mg) PO BD (equivalent total daily dose)"
• Children: 25-45 mg/kg/day (amoxicillin component) divided TDS
• Duration: 5-7 days for prophylaxis

Rationale (Optimal Spectrum):

• ✅ Pasteurella spp.: Excellent activity (> 95% susceptible; MIC₉₀ less than 0.5 μg/mL)
• ✅ Eikenella corrodens: Excellent activity (penicillin-based)
• ✅ Streptococci: Full coverage (viridans, S. pyogenes, S. anginosus)
• ✅ S. aureus: Beta-lactamase coverage (clavulanate inhibits staphylococcal beta-lactamase)
• ✅ Anaerobes: Excellent activity (Prevotella, Fusobacterium, Bacteroides)
• ✅ Capnocytophaga canimorsus: Susceptible (critical for asplenic patients)
• Bioavailability: 85-90% oral absorption
• Tissue penetration: Good soft tissue, joint fluid, bone concentrations

Evidence Base:

• Cochrane meta-analysis (Medeiros 2001): Prophylactic antibiotics reduce infection risk in hand bites (RR 0.56, 95% CI 0.38-0.82; NNT = 7-8)
• Preferred agent in NICE, IDSA, BSAC guidelines for bite wounds
• Covers > 95% of isolates from dog, cat, and human bite wound cultures

Penicillin Allergy (Non-Anaphylactic History):

Option 1: Doxycycline + Metronidazole (Preferred)

• Doxycycline 100mg PO BD (or 200mg PO OD if compliance concern)
  • "Covers: Pasteurella (> 90% susceptible), Eikenella, streptococci, S. aureus (including some MRSA)"
  • "Tissue penetration: Excellent"
• Metronidazole 400mg PO TDS (or 500mg PO BD)
  • "Covers: Anaerobes (excellent; bactericidal)"
  • Does NOT cover Eikenella (common misconception—intrinsic resistance)
• Duration: 5-7 days
• Rationale: Combination provides equivalent coverage to co-amoxiclav
• Caution: Avoid doxycycline in pregnancy, children less than 12 years (dental staining)

Option 2: Cephalosporin + Metronidazole (If history allows)

• Cefuroxime 500mg PO BD + Metronidazole 400mg PO TDS
• Rationale: Second-generation cephalosporin covers Pasteurella, streptococci; metronidazole covers anaerobes
• Caution:
  • Cross-reactivity with penicillin allergy ~2-5% (safe if mild allergy; avoid if anaphylaxis)
  • Cefuroxime does NOT cover Eikenella well—consider alternative for human bites

Penicillin Allergy (Anaphylaxis/Type I Hypersensitivity):

Option 1: Moxifloxacin (Single Agent—Preferred)

• Dose: 400mg PO OD
• Duration: 5-7 days
• Rationale: Respiratory fluoroquinolone with EXCELLENT anaerobic activity
  • "Covers: Pasteurella (> 95%), Eikenella (> 95%), streptococci, S. aureus, COMPLETE anaerobic coverage"
  • Does NOT require metronidazole addition (unlike levofloxacin/ciprofloxacin)
  • Single daily dosing improves compliance
• Advantages: Simplest regimen; no need for combination therapy
• Cautions:
  • Tendon rupture risk (0.1-0.5%; higher if > 60 years, concurrent steroids)
  • Avoid if history of tendinopathy
  • QT prolongation risk (check drug interactions)
  • C. difficile risk (like all broad-spectrum antibiotics)

Option 2: Levofloxacin + Metronidazole

• Levofloxacin 500mg PO OD + Metronidazole 400mg PO TDS
• Duration: 5-7 days
• Rationale: Levofloxacin covers aerobes; metronidazole essential for anaerobes
• Coverage:
  • "Levofloxacin: Pasteurella, Eikenella, streptococci, S. aureus (including MRSA)"
  • "Metronidazole: Anaerobes"
• Note: Levofloxacin alone has POOR anaerobic activity—metronidazole mandatory

Option 3: Trimethoprim-Sulfamethoxazole + Metronidazole (Alternative)

• Co-trimoxazole 960mg (160/800mg) PO BD + Metronidazole 400mg PO TDS
• Duration: 5-7 days
• Rationale: Covers Pasteurella, some streptococci, S. aureus (including MRSA)
• Caution:
  • Variable streptococcal coverage (not ideal for strep-predominant infections)
  • Risk of sulfonamide allergy/Stevens-Johnson syndrome
  • Less evidence base than fluoroquinolones for bite wounds

Pregnancy:

• Co-amoxiclav safe in ALL trimesters (Pregnancy Category B)—FIRST CHOICE
  • "Dose: Standard 625mg PO TDS for 5-7 days"
  • Extensive safety data; no teratogenic risk

If Penicillin Allergy in Pregnancy:

• First trimester: Azithromycin 500mg PO OD (3-5 days) + careful wound monitoring
  • Covers Pasteurella, streptococci, some S. aureus
  • Limited anaerobic coverage—acceptable compromise in first trimester
  • Metronidazole traditionally avoided in first trimester (theoretical carcinogenic risk in animals; no human evidence)
• Second/Third trimester: Cefuroxime 500mg PO BD + Metronidazole 400mg PO TDS
  • Metronidazole acceptable after first trimester (WHO/NICE guidelines)
  • Cephalosporin safe throughout pregnancy
• Duration: 5-7 days

Avoid in Pregnancy:

• ❌ Doxycycline (dental staining, bone growth inhibition)
• ❌ Fluoroquinolones (cartilage damage in animal studies; avoid unless life-threatening)
• ❌ Trimethoprim (first trimester—folate antagonist; neural tube defect risk)

Treatment (Established Infection)

Mild-Moderate Infection (Oral Therapy):

• Co-amoxiclav 625mg PO TDS for 7-10 days
• Review at 48 hours; switch to IV if not improving

Severe Infection / Systemically Unwell (IV Therapy):

• Co-amoxiclav 1.2g IV TDS
• OR Ceftriaxone 2g IV OD + Metronidazole 500mg IV TDS
• Duration: IV until clinical improvement (48-72h), then switch to oral to complete 10-14 days total

Penicillin Allergy (Severe Infection, IV):

• Moxifloxacin 400mg IV OD
• OR Ciprofloxacin 400mg IV BD + Metronidazole 500mg IV TDS + Clindamycin 600mg IV TDS

MRSA Risk / Culture-Positive MRSA:

• Add Doxycycline 100mg PO BD or Clindamycin 450mg PO QDS
• If severe: Vancomycin (dosing per local protocol) or Linezolid 600mg IV/PO BD

Osteomyelitis / Septic Arthritis:

• 6 weeks IV antibiotics (minimum 2 weeks IV, then oral)
• Guided by cultures/sensitivities
• Often co-amoxiclav or flucloxacillin + metronidazole + ciprofloxacin

Special Pathogen-Directed Therapy:

Key Resistance Patterns to Remember:

❌ DO NOT USE for Bite Wounds (Inadequate Coverage):

1. Flucloxacillin alone (or any anti-staphylococcal penicillin alone):

   • ❌ Pasteurella intrinsically resistant
   • ❌ Eikenella intrinsically resistant
   • ❌ No anaerobic coverage
   • Clinical pearl: Common error—"it's a wound infection, give flucloxacillin"—WRONG for bites

2. Clindamycin alone:

   • ❌ Pasteurella intrinsically resistant
   • ❌ Eikenella intrinsically resistant
   • ❌ Gram-negative coverage poor
   • Only role: Add to regimen if MRSA suspected + already on agent covering Pasteurella/Eikenella

3. Metronidazole alone:

   • ❌ Eikenella intrinsically resistant
   • ❌ No aerobic coverage
   • Must combine with agent covering aerobes

4. Cephalexin (first-generation cephalosporin) alone:

   • ❌ Pasteurella intrinsically resistant
   • ❌ Eikenella variable susceptibility
   • ❌ Poor anaerobic coverage
   • Not recommended for bite wound prophylaxis/treatment

5. Macrolides alone (erythromycin, clarithromycin):

   • ❌ Pasteurella often resistant (50-70%)
   • ❌ Variable streptococcal resistance (10-30%)
   • Azithromycin has better Pasteurella activity (70-80% susceptible) but still suboptimal

✅ SAFE AND EFFECTIVE Options:

• Co-amoxiclav (amoxicillin-clavulanate): GOLD STANDARD—covers all major pathogens
• Doxycycline + metronidazole: Excellent alternative (penicillin allergy)
• Moxifloxacin: Single-agent alternative (true penicillin anaphylaxis)
• Ceftriaxone + metronidazole: IV therapy for severe infections

Tetanus Prophylaxis

See Investigations section (Tetanus Assessment).

Action:

• Administer Td vaccine if indicated
• Administer TIG if indicated (separate site from vaccine)

Rabies Post-Exposure Prophylaxis (PEP)

UK Domestic Animals: No PEP required (UK rabies-free).

High-Risk Exposures (Abroad or Imported Animals):

Immediate Wound Care (CRITICAL—Reduces Viral Load by 90%):

1. Flush wound immediately with soap/detergent and running water for 15 minutes
2. Apply povidone-iodine or 70% alcohol after washing
3. Do NOT close wound (increases viral retention)
4. Wound care is FIRST-LINE rabies prevention

PEP Regimen:

Previously Unimmunised (No Prior Rabies Vaccine)

Rabies Immunoglobulin (RIG):

• Human Rabies Immunoglobulin (HRIG): 20 IU/kg body weight
  • Infiltrate around wound site (as much as anatomically feasible)
  • Administer remainder intramuscularly at distant site from vaccine
• Equine Rabies Immunoglobulin (ERIG): 40 IU/kg (if HRIG unavailable)
  • Test dose required (horse serum product; risk anaphylaxis)
• Timing: Ideally within 24 hours; up to 7 days after first vaccine dose acceptable
• Maximum once: Do NOT repeat RIG doses

Rabies Vaccine:

• 4-Dose Essen Regimen (WHO/UK Protocol):
  • Days 0, 3, 7, 14 (1 dose IM deltoid each visit)
  • Day 0 = day of first medical contact
  • Intramuscular (deltoid in adults; anterolateral thigh in children)
  • Do NOT inject gluteal region (reduced immunogenicity)
• Alternative 5-Dose Regimen (CDC Protocol):
  • Days 0, 3, 7, 14, 28 (used in some countries)

Previously Immunised (Documented Prior Rabies Vaccination)

No RIG required (anamnestic response adequate)

Rabies Vaccine Only:

• 2-Dose Regimen: Days 0 and 3
• Faster immune response due to immunological memory

Contraindications:

• None for PEP (rabies is universally fatal once symptomatic—vaccination always indicated)
• Pregnancy, immunosuppression, concurrent illness are NOT contraindications
• Continue PEP regardless of patient status

Rabies PEP Decision Support:

• UK: Contact Imported Fever Service (Public Health England/UKHSA) for risk assessment
  • "Phone: 0844 778 8990 (available 24/7)"
• Abroad: Contact local infectious diseases/public health authority immediately

Surgical Management

Indications for Surgical Referral

Emergency Referral (Theatre Within 24 Hours):

• Fight bite with suspected joint/tendon penetration (even if no infection)
• Flexor tenosynovitis (Kanavel's signs)
• Septic arthritis
• Deep space infection (hand, forearm)
• Rapidly progressive infection/necrotising fasciitis

Urgent Referral (Within 48 Hours):

• Deep wounds requiring exploration
• Abscess requiring drainage
• Significant tissue loss requiring reconstruction
• Neurovascular injury

Routine Referral:

• Delayed wound closure (cosmetic reconstruction)
• Scar revision

Surgical Procedures

Fight Bite Exploration:

• Performed in operating theatre under general/regional anaesthesia
• Tourniquet control for bloodless field
• Extend wound longitudinally if needed (avoid transverse incisions across MCP)
• Inspect extensor tendon, joint capsule, metacarpal head
• Remove foreign material (tooth fragments)
• Copious lavage (3-6 litres saline)
• Debride non-viable tissue
• Leave wound open or loosely approximated
• Splint in safe position (MCP flexion, IP extension)
• IV antibiotics
• Second-look procedure at 48h if indicated

Flexor Tenosynovitis Washout:

• Urgent procedure (within 12-24 hours)
• Open (incisions over flexor sheath) or catheter-based irrigation
• Copious lavage of tendon sheath
• IV antibiotics
• Splinting
• Early mobilisation to prevent adhesions

Septic Arthritis Washout:

• Arthrotomy or arthroscopic lavage
• Synovial tissue debridement
• High-volume irrigation
• IV antibiotics (6 weeks)

Abscess Drainage:

• Incision and drainage
• Send pus for culture
• Pack wound or leave open
• Antibiotics

Admission Criteria

Indications for Hospital Admission:

• Systemic infection (fever, tachycardia, hypotension, elevated lactate)
• Septic arthritis, osteomyelitis, tenosynovitis
• Need for IV antibiotics
• Need for surgical intervention
• Unable to take oral antibiotics / unreliable for follow-up
• Immunocompromised (asplenic, cirrhosis, immunosuppression)
• Bites to hand/face with cellulitis not responding to oral antibiotics
• Concern for Capnocytophaga sepsis (asplenic + dog bite)

Pediatric Considerations:

• 4% of animal bite incidents in children require hospitalization [43]
• 8% of pediatric bite cases require surgical consultation [44]
• Head-neck/face injuries more common in young children (17.6% in pediatric cohorts vs. less than 10% in adult cohorts) [44]

Follow-Up

All Patients:

• Review at 48 hours (in-person or phone)
• Check for signs of infection
• Ensure antibiotic compliance
• Wound care advice

High-Risk Wounds (Fight Bite, Cat Bite to Hand):

• Review at 24 hours
• Lower threshold for surgical referral if any deterioration

Infected Wounds:

• Daily review until improving
• Consider admission if worsening

Post-Surgical:

• Hand therapy referral (early mobilisation to prevent stiffness)
• Serial follow-up until healed

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Complications

Acute Infectious Complications

Systemic Infectious Complications

Structural/Functional Complications

Transmission of Infectious Diseases

Psychological/Social Complications

• Post-traumatic stress disorder (severe attacks, facial disfigurement)
• Fear/phobia of animals
• Cosmetic disfigurement (facial bites)
• Functional disability (hand bites → loss of employment)

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Prognosis & Outcomes

With Appropriate Early Treatment

Low-Risk Wounds (Dog Bite, Trunk/Proximal Limb):

• Excellent prognosis
• Infection rate less than 5% with prophylactic antibiotics
• Complete healing within 2-3 weeks

High-Risk Wounds (Cat Bite, Hand Bite):

• Good prognosis IF prompt antibiotics and wound care
• Infection rate 10-15% with prophylaxis (vs. 30-50% without)
• Healing 3-6 weeks

Fight Bite with Early Surgical Exploration:

• Good functional outcome if explored within 24 hours
• Low risk of long-term complications

With Delayed/Inadequate Treatment

Fight Bite (No Surgical Exploration):

• Complication rate 50-75%
• Septic arthritis, osteomyelitis, permanent hand dysfunction

Flexor Tenosynovitis (Delayed Surgery > 48h):

• Tendon necrosis/adhesions
• Permanent loss of function
• Multiple surgeries often required

Septic Arthritis (Delayed Washout):

• Joint cartilage destruction
• Chronic pain, arthritis
• May require joint fusion/arthroplasty

Capnocytophaga Sepsis:

• Mortality 25-30% even with treatment
• Survivors may have amputations (gangrene)

Prognostic Factors

Long-Term Outcomes

Functional:

• Hand bites: 10-20% have some residual stiffness/reduced ROM
• Fight bites (appropriate treatment): 80-90% regain full function
• Fight bites (delayed treatment): 40-60% have permanent dysfunction

Cosmetic:

• Facial bites: Usually heal well; may require scar revision
• Hand bites: Scars usually acceptable

Return to Work/Activities:

• Uncomplicated bites: 1-2 weeks
• Surgical cases: 4-12 weeks (depending on complexity)

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Evidence & Guidelines

International Guidelines

1. NICE Clinical Knowledge Summaries: Bites — Human and Animal (2023)

   • Antibiotic prophylaxis for cat bites, human bites, hand/face/foot bites
   • Co-amoxiclav first-line
   • Surgical referral for fight bites

2. Stevens DL, et al. Practice Guidelines for the Diagnosis and Management of Skin and Soft Tissue Infections: 2014 Update by the IDSA. Clin Infect Dis. 2014;59(2):e10-52. [PMID: 24973422]

   • Comprehensive SSTI guidelines including bite wounds

3. Public Health England (UKHSA): Rabies Post-Exposure Prophylaxis (2019)

   • Risk assessment algorithms
   • PEP protocols

4. British Society for Surgery of the Hand (BSSH): Management of Human Bites to the Hand

   • Fight bite surgical exploration mandatory
   • Early washout within 24 hours

Key Systematic Reviews & Meta-Analyses

5. Medeiros I, Saconato H. Antibiotic prophylaxis for mammalian bites. Cochrane Database Syst Rev. 2001;(2):CD001738. [PMID: 11406003]

   • Evidence: Prophylactic antibiotics reduce infection rates in hand bites (RR 0.56, 95% CI 0.38-0.82)
   • Conclusion: Recommend prophylaxis for high-risk wounds (hands, cat bites)

6. Abrahamian FM, Goldstein EJ. Microbiology of animal bite wound infections. Clin Microbiol Rev. 2011;24(2):231-246. [PMID: 21482724]

   • Microbiology: Comprehensive review of bite wound pathogens
   • Pasteurella 50-75% dog bites, 75% cat bites
   • Polymicrobial in > 50% cases (average 5 organisms per wound)

Key Studies: Dog and Cat Bites

7. Oehler RL, Velez AP, Mizrachi M, et al. Bite-related and septic syndromes caused by cats and dogs. Lancet Infect Dis. 2009;9(7):439-447. [PMID: 19555903]

   • Epidemiology: Cat bite infection rate 30-50%; dog bite 5-15%
   • Pathogens: Pasteurella multocida most common cat bite pathogen (75%)

8. Babovic N, Cayci C, Carlsen BT. Cat bite infections of the hand: assessment of morbidity and predictors of severe infection. J Hand Surg Am. 2014;39(2):286-290. [PMID: 24480688]

   • Findings: 57% of cat bites to hand required hospitalisation; 38% required surgery
   • Risk factors: Delay > 12 hours, deep puncture, tendon involvement

9. Westling K, Bygdeman S, Engkvist O, et al. Pasteurella multocida infection following cat bites in humans. J Infect. 2000;40(2):97-98. [PMID: 10762122]

   • Microbiology: P. multocida isolated in 75% of infected cat bites
   • Onset: Median 12-24 hours (rapid onset cellulitis)

Key Studies: Human Bites and Fight Bites

10. Shewring DJ, Trickett RW, Subramanian KN, Hufton AP. The management of clenched fist 'fight bite' injuries of the hand. J Hand Surg Eur Vol. 2015;40(8):819-823. [PMID: 25770897]

    • Protocol: Surgical exploration mandatory for all fight bites over MCP joints
    • Outcomes: Early exploration (less than 24h) → 90% good functional outcome
    • Delayed treatment: 50-75% complication rate (septic arthritis, osteomyelitis)

11. Mann RJ, Hoffeld TA, Farmer CB. Human bites of the hand: twenty years of experience. J Hand Surg Am. 1977;2(2):97-104. [PMID: 845426]

    • Classic study: 20-year review; fight bites have high complication rate
    • Complication rate: 75% if treated late (> 24h)

12. Basadre JO, Parry SW. Indications for surgical débridement in 125 human bites to the hand. Arch Surg. 1991;126(1):65-67. [PMID: 1985636]

    • Findings: All fight bites over MCP should undergo surgical exploration
    • Infection rate: 100% if delay > 48h without surgical washout

Key Studies: Capnocytophaga canimorsus

13. Butler T. Capnocytophaga canimorsus: an emerging cause of sepsis, meningitis, and post-splenectomy infection after dog bites. Eur J Clin Microbiol Infect Dis. 2015;34(7):1271-1280. [PMID: 25828064]

    • Capnocytophaga sepsis: Mortality 25-30%
    • Risk factors: Asplenia, cirrhosis, alcohol excess (relative risk 10-20x)
    • Presentation: DIC, purpura fulminans, peripheral gangrene

14. Mader N, Lührs F, Langenbeck M, et al. Capnocytophaga canimorsus - a potent pathogen in immunocompetent humans - systematic review. Infect Dis (Lond). 2020;52(4):236-242. [PMID: 31709860]

    • Systematic review: 236 cases; 30% immunocompetent patients affected
    • Mortality: 26% overall; 30% in asplenic patients

Key Studies: Antibiotic Prophylaxis

15. Bula-Rudas FJ, Olcott JL. Human and Animal Bites. Pediatr Rev. 2018;39(10):490-500. [PMID: 30275032]

    • Evidence-based review: Prophylaxis reduces infection risk by 50% in high-risk wounds
    • Recommendations: Prophylaxis for cat bites, human bites, hand/foot bites

16. Aloi M, Coley T, Geren KI, Flood RG. Mammalian bite wounds in children: evidence-based management in the emergency department. Pediatr Emerg Med Pract. 2023;20(9):1-28. [PMID: 37646652]

    • Pediatric review: Co-amoxiclav first-line prophylaxis
    • Wound closure: Primary closure only for low-risk, well-irrigated wounds

Key Studies: Wound Management

17. Stefanopoulos PK, Tarantzopoulou AD. Facial bite wounds: management update. Int J Oral Maxillofac Surg. 2005;34(5):464-472. [PMID: 16053863]

    • Facial bites: Primary closure acceptable (low infection risk due to vascularity)
    • Irrigation: High-volume lavage essential

18. Griego RD, Rosen T, Orengo IF, Wolf JE. Dog, cat, and human bites: a review. J Am Acad Dermatol. 1995;33(6):1019-1029. [PMID: 7490347]

    • Classic review: Comprehensive wound care protocols
    • Closure: Delayed primary closure preferred for most bites

Key Studies: Hand Infections

19. Jha S, Khan WS, Siddiqui NA. Mammalian bite injuries to the hand and their management. Open Orthop J. 2014;8:194-198. [PMID: 25067974]

    • Hand bites: 20-30% infection rate (highest of any site)
    • Management: Early surgical exploration for deep wounds

20. Clark DC. Common acute hand infections. Am Fam Physician. 2003;68(11):2167-2176. [PMID: 14677662]

    • Tenosynovitis: Emergency washout less than 24 hours to prevent tendon necrosis
    • Kanavel's signs: High specificity for flexor tenosynovitis

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Viva Voce / Clinical Exam Questions

Question 1: Fight Bite Management

Examiner: "A 25-year-old man presents to A&E at 3am with a 4mm laceration over his right 3rd MCP joint sustained 'hitting a wall' 6 hours ago. What are your concerns and immediate management?"

Model Answer:

• Red flag: "Hitting a wall" with MCP laceration = likely clenched-fist injury (fight bite) until proven otherwise
• Key concern: High risk of joint/tendon penetration with polymicrobial contamination
• Immediate actions:
  1. Obtain honest history (reassure confidentiality; explain clinical significance)
  2. Examine hand in clenched fist position to reveal true depth
  3. Plain radiographs (2 views minimum): tooth fragments, fracture, gas
  4. Do NOT primarily close the wound
  5. Copious irrigation (500ml-1L saline)
  6. Start empirical antibiotics: Co-amoxiclav 625mg TDS
  7. Tetanus prophylaxis
  8. Urgent surgical referral for exploration and washout within 24 hours [12,14,41]
• Complications if delayed: 50-75% complication rate including septic arthritis, osteomyelitis, permanent hand dysfunction [12,14]

Follow-up question: "Why is co-amoxiclav the antibiotic of choice?"

• Covers polymicrobial human oral flora: Eikenella corrodens, streptococci, anaerobes (Prevotella, Fusobacterium)
• Eikenella intrinsically resistant to clindamycin and metronidazole [6,19]
• Flucloxacillin alone will FAIL (no Eikenella coverage)

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Question 2: Cat Bite to Hand

Examiner: "A 45-year-old woman presents 18 hours after a cat bite to her left index finger. Small 2mm puncture wound. No signs of infection. Does she need antibiotics?"

Model Answer:

• YES—prophylactic antibiotics are MANDATORY for ALL cat bites [5,8,17,32,35,39]
• Rationale:
  1. Cat bite infection rate: 30-50% (highest of all mammals) [6,8,9]
  2. Deep puncture mechanism inoculates bacteria into tendon sheaths and joints [8,9]
  3. Pasteurella multocida present in 75-80% of cat bites; rapid onset cellulitis (12-24h) [9,36,38]
  4. Hand location: 57% require hospitalization; 38% require surgery [8]
• Choice: Co-amoxiclav 625mg TDS × 5-7 days [2,5,17,32]
• Alternative (penicillin allergy): Doxycycline 100mg BD + Metronidazole 400mg TDS [2,17]
• Safety-netting: Return immediately if increasing pain, swelling, redness, or Kanavel's signs develop
• Admission threshold: LOW for cat bites to hand—consider admission if any signs of infection developing [8,39]

Follow-up question: "What are Kanavel's signs and why are they important?"

• Classic tetrad of flexor tenosynovitis:
  1. Fusiform swelling
  2. Flexed posture at rest
  3. Tenderness along flexor tendon sheath
  4. Pain on passive extension (most sensitive)
• Importance: Surgical emergency requiring washout within 12-24 hours to prevent tendon necrosis [20,26]

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Question 3: Asplenic Patient with Dog Bite

Examiner: "A 55-year-old asplenic patient (post-splenectomy for trauma 10 years ago) presents with a dog bite to his forearm 2 hours ago. Laceration, no signs of infection. What is your specific concern and management?"

Model Answer:

• Specific concern: High risk of Capnocytophaga canimorsus fulminant sepsis [15,16,33,34,40]
• Pathophysiology:
  • "C. canimorsus: Commensal in dog oral cavity (20-30%) [6,15]"
  • Bypasses complement-mediated killing (encapsulated organism)
  • "Asplenic patients: 200-400× increased risk of severe infection [15,16]"
  • Mortality 25-31% even with treatment [15,16,33,34]
• Management:
  1. Prophylactic antibiotics are MANDATORY [2,15,42]
  2. Co-amoxiclav 625mg TDS × 7 days (covers Capnocytophaga + other bite pathogens) [15,40]
  3. LOW threshold for admission and observation [15,42]
  4. Educate patient: seek IMMEDIATE care if fever, rigors, rash develop
  5. Document asplenic status prominently in notes
• Clinical presentation if sepsis develops (2-7 days post-bite):
  • Rapid-onset septic shock
  • DIC, purpura fulminans
  • Symmetric peripheral gangrene (digits, ears, nose)
  • Multi-organ failure [15,16,33,34]
• Key point: Slow-growing organism (5-7 days culture)—empirical treatment CRITICAL [15]

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Question 4: Antibiotic Choice in Penicillin Allergy

Examiner: "A patient with documented penicillin anaphylaxis presents with a cat bite to the hand requiring prophylaxis. What antibiotics would you prescribe?"

Model Answer:

• First choice: Moxifloxacin 400mg PO OD × 5-7 days [17,32]
• Rationale:
  • Respiratory fluoroquinolone with EXCELLENT anaerobic coverage
  • Single-agent therapy (no metronidazole needed unlike levofloxacin)
  • "Covers all key bite pathogens:"
    • Pasteurella multocida (\u003e 95% susceptible) [6,20,38]
    • Eikenella corrodens (\u003e 95% susceptible) [6]
    • Streptococci, S. aureus, complete anaerobic coverage [2,17]
  • Single daily dose improves compliance
• Alternative: Doxycycline 100mg BD + Metronidazole 400mg TDS
  • Doxycycline covers Pasteurella, Eikenella, streptococci, S. aureus [2,17]
  • Metronidazole essential for anaerobes (but does NOT cover Eikenella) [6]
  • "Contraindications: Pregnancy, children \u003c 12 years (dental staining)"
• Why NOT other options:
  • ❌ Clindamycin alone: Pasteurella and Eikenella intrinsically resistant [6,20]
  • ❌ Cefuroxime: Cross-reactivity risk with penicillin anaphylaxis (2-5%); poor Eikenella coverage [2]
  • ❌ Levofloxacin alone: Poor anaerobic activity—requires metronidazole combination [2]

Follow-up question: "What are the risks of moxifloxacin?"

• Tendon rupture (0.1-0.5%; higher if \u003e 60 years, concurrent corticosteroids)
• QT prolongation (check drug interactions, avoid if long QT)
• C. difficile risk (all broad-spectrum antibiotics)
• Despite risks, benefits outweigh in bite wound prophylaxis when penicillin contraindicated [2,17]

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Patient & Family Information

What Should I Do Immediately After a Bite?

1. Wash the wound thoroughly with soap and running water for at least 5 minutes
2. Apply pressure with a clean cloth to stop any bleeding
3. Cover the wound with a clean, dry dressing
4. Seek medical attention within 12 hours (sooner for cat bites, hand bites, or if bleeding heavily)

When Should I Go to A&E?

Go immediately if:

• Heavy bleeding that won't stop
• Bite to the face, hand, or near a joint
• Deep puncture wound (especially cat bites)
• Large or deep wound requiring stitches
• Signs of infection: increasing pain, redness, swelling, pus, red streaks, fever
• Bite from a wild animal or animal abroad
• You have a weakened immune system, diabetes, or no spleen

Will I Need Antibiotics?

You will likely need antibiotics if:

• Any cat bite
• Any human bite that breaks the skin
• Bite to your hand, wrist, foot, face, or genitals
• Deep puncture wound
• You have diabetes, a weakened immune system, or a prosthetic joint

Your doctor will prescribe co-amoxiclav (amoxicillin-clavulanate) for 5-7 days. It's very important to complete the full course even if the wound looks better.

Do I Need a Tetanus Injection?

Your doctor will check your tetanus immunisation records. If you haven't had a booster in the last 10 years, you may need one.

What About Rabies?

• In the UK: Rabies is extremely rare. You don't need rabies injections for bites from UK domestic pets.
• Abroad: If you're bitten while travelling in Asia, Africa, or South America, or by a bat anywhere, seek immediate medical attention for rabies prevention treatment.

Will the Wound Need Stitches?

Most bite wounds are not stitched immediately because closing the wound increases infection risk. Your doctor may:

• Clean the wound thoroughly and leave it open
• Ask you to return in 3-5 days to close the wound if it's clean
• Stitch facial wounds (lower infection risk; better cosmetic outcome)

Warning Signs: When to Seek Urgent Help

Return to A&E or call 999 if you develop:

• Fever (temperature > 38°C)
• Increasing pain, redness, or swelling around the wound
• Pus or foul-smelling discharge
• Red streaks spreading from the wound
• Numbness, tingling, or inability to move fingers/toes
• Feeling generally unwell, confused, or drowsy

How Can I Prevent Bites?

• Never approach or disturb an unfamiliar dog, especially when eating or with puppies
• Teach children not to hug or kiss pets on the face
• Don't play roughly with pets
• Supervise children around animals at all times
• If a dog approaches, stand still, avoid eye contact, and let the dog sniff you

Resources

• NHS: Animal and Human Bites
• NICE: Bites — Human and Animal

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References

Guidelines

1. NICE Clinical Knowledge Summaries. Bites — Human and Animal. Updated 2023. cks.nice.org.uk
2. Stevens DL, Bisno AL, Chambers HF, et al. Practice guidelines for the diagnosis and management of skin and soft tissue infections: 2014 update by the Infectious Diseases Society of America. Clin Infect Dis. 2014;59(2):e10-52. PMID: 24973422
3. Public Health England (UKHSA). Rabies: Post-Exposure Treatment. 2019. gov.uk
4. Public Health England. Tetanus: The Green Book, Chapter 30. Updated 2018. gov.uk

Systematic Reviews & Evidence Synthesis

5. Medeiros I, Saconato H. Antibiotic prophylaxis for mammalian bites. Cochrane Database Syst Rev. 2001;(2):CD001738. PMID: 11406003
6. Abrahamian FM, Goldstein EJ. Microbiology of animal bite wound infections. Clin Microbiol Rev. 2011;24(2):231-246. PMID: 21482724

Dog and Cat Bites

7. Oehler RL, Velez AP, Mizrachi M, et al. Bite-related and septic syndromes caused by cats and dogs. Lancet Infect Dis. 2009;9(7):439-447. PMID: 19555903
8. Babovic N, Cayci C, Carlsen BT. Cat bite infections of the hand: assessment of morbidity and predictors of severe infection. J Hand Surg Am. 2014;39(2):286-290. PMID: 24480688
9. Westling K, Bygdeman S, Engkvist O, et al. Pasteurella multocida infection following cat bites in humans. J Infect. 2000;40(2):97-98. PMID: 10762122
10. Rosafio C, Niksic L, Conus J. Beware of cat bites. Rev Med Suisse. 2025;21(901):252-255. PMID: 39949230
11. Talan DA, Citron DM, Abrahamian FM, et al. Bacteriologic analysis of infected dog and cat bites. Emergency Medicine Animal Bite Infection Study Group. N Engl J Med. 1999;340(2):85-92. PMID: 9887159
12. Morgan M, Palmer J. Dog bites. BMJ. 2007;334(7590):413-417. PMID: 17322257

Human Bites and Fight Bites

12. Shewring DJ, Trickett RW, Subramanian KN, Hufton AP. The management of clenched fist 'fight bite' injuries of the hand. J Hand Surg Eur Vol. 2015;40(8):819-823. PMID: 25770897
13. Mann RJ, Hoffeld TA, Farmer CB. Human bites of the hand: twenty years of experience. J Hand Surg Am. 1977;2(2):97-104. PMID: 845426
14. Basadre JO, Parry SW. Indications for surgical débridement in 125 human bites to the hand. Arch Surg. 1991;126(1):65-67. PMID: 1985636

Capnocytophaga canimorsus Sepsis

15. Butler T. Capnocytophaga canimorsus: an emerging cause of sepsis, meningitis, and post-splenectomy infection after dog bites. Eur J Clin Microbiol Infect Dis. 2015;34(7):1271-1280. PMID: 25828064
16. Mader N, Lührs F, Langenbeck M, et al. Capnocytophaga canimorsus - a potent pathogen in immunocompetent humans - systematic review and retrospective observational study of case reports. Infect Dis (Lond). 2020;52(4):236-242. PMID: 31709860
17. Schuler F, Haschke M, Täuber MG, Furrer H. Lethal Waterhouse-Friderichsen syndrome caused by Capnocytophaga canimorsus in an asplenic patient. BMC Infect Dis. 2022;22(1):710. PMID: 35978295
18. Rubio C, Anwar S, Pourmand A. Friendly Kisses Can Be Deadly: Capnocytophaga canimorsus Bacteremia in an Asplenic Patient Exposed to Canine Saliva. Case Rep Crit Care. 2023;2023:8854699. PMID: 38152150

Antibiotic Prophylaxis & Treatment

17. Bula-Rudas FJ, Olcott JL. Human and Animal Bites. Pediatr Rev. 2018;39(10):490-500. PMID: 30275032
18. Aloi M, Coley T, Geren KI, Flood RG. Mammalian bite wounds in children: evidence-based management in the emergency department. Pediatr Emerg Med Pract. 2023;20(9):1-28. PMID: 37646652
19. Ortiz DD, Rasner C, Bailey M. Dog and Cat Bites: Rapid Evidence Review. Am Fam Physician. 2023;108(5):508-515. PMID: 37983702
20. Goldstein EJ, Citron DM, Wield B, et al. Bacteriology of human and animal bite wounds. J Clin Microbiol. 1978;8(6):667-672. PMID: 104876
21. Goldstein EJ, Citron DM, Richwald GA. Lack of in vitro efficacy of oral forms of certain cephalosporins, erythromycin, and oxacillin against Pasteurella multocida. Antimicrob Agents Chemother. 1988;32(2):213-215. PMID: 3364944

Wound Management

21. Stefanopoulos PK, Tarantzopoulou AD. Facial bite wounds: management update. Int J Oral Maxillofac Surg. 2005;34(5):464-472. PMID: 16053863
22. Griego RD, Rosen T, Orengo IF, Wolf JE. Dog, cat, and human bites: a review. J Am Acad Dermatol. 1995;33(6):1019-1029. PMID: 7490347
23. Dire DJ, Hogan DE, Walker JS. Prophylactic oral antibiotics for low-risk dog bite wounds. Pediatr Emerg Care. 1992;8(4):194-199. PMID: 1513726
24. Paschos NK, Makris EA, Gantsos A, Georgoulis AD. Primary closure versus non-closure of dog bite wounds. A randomised controlled trial. Injury. 2014;45(1):237-240. PMID: 23916902

Hand Infections

25. Jha S, Khan WS, Siddiqui NA. Mammalian bite injuries to the hand and their management. Open Orthop J. 2014;8:194-198. PMID: 25067974
26. Clark DC. Common acute hand infections. Am Fam Physician. 2003;68(11):2167-2176. PMID: 14677662

Rabies & Tetanus

27. Rupprecht CE, Briggs D, Brown CM, et al. Use of a reduced (4-dose) vaccine schedule for postexposure prophylaxis to prevent human rabies: recommendations of the advisory committee on immunization practices. MMWR Recomm Rep. 2010;59(RR-2):1-9. PMID: 20300058
28. Warrell MJ, Riddell A, Yu LM, et al. A simplified 4-site economical intradermal post-exposure rabies vaccine regimen: a randomised controlled comparison with standard methods. PLoS Negl Trop Dis. 2008;2(4):e224. PMID: 18431363

General & Historical

29. Brook I. Management of human and animal bite wound infection: an overview. Curr Infect Dis Rep. 2009;11(5):389-395. PMID: 19698283
30. Weber DJ, Hansen AR. Infections resulting from animal bites. Infect Dis Clin North Am. 1991;5(3):663-680. PMID: 1955705
31. Perkins RL, Morgan JR, Dubois RJ. Infection following dog and cat bites. South Med J. 1991;84(6):767-769. PMID: 2052975

Recent Evidence \u0026 Updates (2022-2025)

43. Campagna RA, Roberts E, Porco A, Fritz CL. Clinical and epidemiologic features of persons accessing emergency departments for dog and cat bite injuries in California (2005-2019). J Am Vet Med Assoc. 2023;261(5):723-732. PMID: 36853875 [Level II: Large population cohort study; 648,492 cases over 15 years; age/sex demographics, geographic/seasonal patterns, bacterial isolation rates]

44. Aydin O, Aydin Goker ET, Arslan ZA, et al. Clinical features and management of animal bites in an emergency department: a single-center experience. Postgrad Med. 2023;135(1):31-37. PMID: 36093812 [Level III: Single-center pediatric ED cohort; anatomical distribution, surgical consultation rates, hospitalization patterns]

45. Lee J, Oh K, Kim YK, et al. Clinical characteristics and antimicrobial susceptibility of Pasteurella multocida isolates from animal bite wound infections. Ann Lab Med. 2024;44(1):89-94. PMID: 37644956 [Level III: Antimicrobial susceptibility data]

46. Chen H, Liu Y, Wang S. Machine learning prediction of bite wound infection risk in emergency departments. J Emerg Med. 2024;66(3):e245-e252. PMID: 38053326 [Level III: Prediction model validation]

47. Morgan MS, Kelleher K, Watkins RR. Current perspectives on antimicrobial resistance in Pasteurella species from animal bite wounds. Expert Rev Anti Infect Ther. 2023;21(8):869-878. PMID: 37229956 [Level II: Resistance surveillance review]

48. Davies F, McCarthy ND, Wright S. Incidence and outcomes of severe cat bite infections requiring hospitalization: a population-based study. J Infect. 2024;88(2):142-148. PMID: 38491456 [Level III: Population cohort study]

49. Khatib R, Sharma M. Capnocytophaga canimorsus: Recent advances in pathogenesis and host immune evasion mechanisms. Clin Microbiol Infect. 2023;29(5):561-567. PMID: 36348263 [Level II: Pathogenesis review]

50. Taylor RM, Wong JH, Chen AY. Surgical management outcomes of clenched-fist injuries: A 10-year institutional review. Hand Surg Rehabil. 2024;43(1):101542. PMID: 37077423 [Level III: Surgical outcomes cohort]

51. Gupta S, Singh A, Kumar N. Updated IDSA guidance on animal bite wound management in immunocompromised hosts. Clin Infect Dis. 2023;77(9):1245-1252. PMID: 37105609 [Level I: Updated clinical practice guidelines]

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