Animal and human bites
Animal and human bites are contaminated wounds whose organism profile depends on the biter, Pasteurella multocida from cats and dogs, Eikenella corrodens and group A Streptococcus from humans, and every wound needs irrigation plus an independent assessment for rabies and tetanus risk. First-line prophylaxis or treatment is amoxicillin-clavulanate 875/125 mg PO every 12 hours, with human and cat bites carrying the highest infection risk and any hand or joint-adjacent wound treated as high risk for septic arthritis or osteomyelitis.
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What this article covers
- Overview
Definition: animal and human bites are contaminated, often crush-and-tear wounds inoculated with the biting mouth's oral flora and the victim's own skin flora.
- Epidemiology
Risk of infection by source: human bites carry the highest risk of infection, followed by cat bites, then dog bites, reflecting the density and pathogenicity of the inoculated oral flora.
- Risk factors
Bite by a human or a cat: confers the highest infection risk among common bite sources.
- Pathophysiology
Inoculation of oral flora into torn tissue: crush injury, laceration, and direct inoculation with the biting mouth's flora together favor both aerobic and anaerobic infection.
- Clinical features
Visible puncture, laceration, or crush wound at the bite site, with the biter's identity and the circumstances of the bite determining risk stratification.
- Differential diagnosis
Necrotizing fasciitis: unlike bite-wound cellulitis, shows crepitus, spreading discoloration, and pain out of proportion to exam, requiring emergent debridement.
- Diagnosis
Diagnosis of an infected bite wound is clinical, based on a bite history plus local erythema, warmth, swelling, and pain; no single test is required, and the workup instead assesses severity and excludes deep-space or bone involvement.
- Management
First, irrigate the wound thoroughly to reduce bacterial inoculum before deciding on closure or antibiotics.
- Complications
Necrotizing fasciitis: usually from a polymicrobial infection or toxin-producing group A Streptococcus, requiring debridement plus clindamycin and a beta-lactam; mortality is 30% in previously…
- Prognosis
Good with prompt irrigation, appropriate antibiotics, and early recognition of deep-space or joint involvement; most bite wounds heal without sequelae.
- Prevention
Prophylaxis for all human bites and for animal bites with a high-risk feature (immunocompromise, a wound near a joint or bone, or crush injury/edema), using amoxicillin-clavulanate 875/125 mg PO every 12 hours for 3 to 5 days.
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