DESCRIPTION

A bite to the human skin and/or subcutaneous tissues by another mammal causing local, and in some cases systemic, effects

EPIDEMIOLOGY

• Animal bites
  • Approximate frequency
    • Dogs: 80–90%
    • Cats: 5–15%
    • Rodents or rabbits: 1%
    • Raccoons and other animals: 1%
  • The offending animals are often well known to the victim.
  • Children are the most common victims:
    • Boys are more likely than girls to be bitten by dogs.
    • Girls are more likely to be bitten by cats.
• Human bites
  • Third most common cause of all bites seen in ED
  • Younger children more often present with occlusion bites (which generally compress tissue causing ecchymoses).
  • Children >10 years old are more likely to present due to accidental injury during sports activities or intentionally during altercations or abusive situations. These are more likely to be due to clenched fist/fight bites (puncture wounds when fist hits teeth).

GENERAL-PREVENTION

• Ensure that children receive routine immunizations against tetanus and hepatitis and that family pets are immunized against rabies.
• Never leave small children alone with pets.
• Encourage children to avoid contact with wild animals and dead animals.

PATHOPHYSIOLOGY

• Injury associated with bite types:
  • Dog
    • Younger children more often have head and neck bites; older children more often extremities are affected.
    • Crush and tear injuries
    • May involve bone
  • Cat
    • Puncture-type wounds
    • Penetrate deeper and carry a higher risk of infection (think osteomyelitis, septic arthritis)
  • Human
    • Generally only violate skin
    • However, clenched fist/fight bites tend to be worse due to the possibility of penetrating injury.
    • Penetration into joint and tendon sheath spaces can occur (especially bites overlying the metacarpal-phalangeal areas).
• Infection
  • Animal bites are considered grossly contaminated.
  • Infections are most commonly polymicrobial with both aerobic and anaerobic organisms.
  • Infected dog and cat bites
    • Pasteurella species are the most frequent isolates.
    • Dog: Pasteurella canis, new emerging bacteria Capnocytophaga species (can cause endocarditis, meningitis, sepsis)
    • Cat: Pasteurella multocida and Pasteurella septica
    • Common anaerobes include Fusobacterium, bacteroides, Porphyromonas, and Prevotella.
  • Infected human bites
    • Streptococcus anginosus
    • Staphylococcus aureus
    • Eikenella corrodens
    • Fusobacterium species
    • Prevotella species