DESCRIPTION

An acute disruption of the human skin secondary to the bite of another mammal causing local tissue damage and, in some cases, systemic effects

EPIDEMIOLOGY

• Account for approximately 1% of all emergency department visits yearly in the United States
• Dog, cat, and human bites account for >95% of all bites.
• Animal bites
  • Dog: 60–90%
  • Cat: 5–20%
  • Rabbits, squirrels, or other rodents: 1%
  • Raccoons and other animals: 1%
  • Offending animal is often well known to the victim.
  • Cat bites are more likely than dog bites to be provoked.
  • Males and younger children are more likely to be bitten by dogs.
  • Children <6 years of age account for 50% of all dog bites.
  • Females and older children are more likely to be bitten by cats.
• Human bites
  • In younger children, human bite injuries are more likely compression or crush injuries and less frequently break skin (i.e., biting at day care).
  • In older children, human bite injuries are most likely secondary to an accidental injury in a sports/recreational injury or intentionally during altercations or abusive situations.
  • Bite injuries secondary to altercations are more likely to be puncture wounds from a fist hitting teeth.
• Estimated number of bites per year in adults and children
  • Dog: 4,500,000
  • Cat: 400,000
  • Human: 250,000
  • Incidence likely greater secondary to underreporting

GENERAL PREVENTION

• Ensure that all family pets receive necessary vaccines, including the rabies vaccination series.
• Ensure children are up to date on vaccinations, including tetanus and hepatitis.
• Consider developmentally appropriate materials to educate children about potential dangers of pets and other animals.
• Separate children from pets while feeding.
• Never leave small children alone with pets.

PATHOPHYSIOLOGY

• Age
  • Younger children are more likely to be bitten on the face, head, and neck given their shorter stature.
  • Older children, similar to adults, are more likely to be bitten on extremities.
• Dog
  • More often crush and tear injuries; may involve bone
  • In younger children <6 years of age, facial injuries requiring operative repair are more likely.
  • Bites to the head may cause skull fracture or pneumocephalus depending on dog breed.
• Cat
  • More often puncture wounds
  • Deeper penetration of wound results in higher risk of infection (e.g., septic arthritis, bacteremia). Presentation is often delayed until infection is apparent.
• Human
  • Often crush injuries or only violate epidermis
  • Clenched fist injuries are at higher risk of a puncture wound and therefore higher risk of infection given the contact with oral flora.
  • Risk of joint space involvement, especially for bite injuries in the hand
• Infection
  • Mammalian bites are considered grossly contaminated. Wound is more likely colonized by mammal’s oral microbiota rather than patient’s skin microbiota.
  • Estimated infection rate:
    • Human: 10%
    • Dog: 20%
    • Cat: 50%
  • Often, infections are polymicrobial with both aerobic and anaerobic organisms.
• Infected dog and cat bites
  • Pasteurella species are most common isolate.
    • 75% in cats (Pasteurella multocida and Pasteurella septica)
    • 50% in dogs (Pasteurella canis)
  • Capnocytophaga species found in dogs can cause bacteremia and sepsis, especially in asplenic patients.
  • Common anaerobes: Fusobacterium, bacteroides, Porphyromonas, and Prevotella.
• Human bite infection
  • Streptococcus anginosus
  • Staphylococcus aureus
  • Eikenella corrodens
  • Fusobacterium species
  • Prevotella species
• Pathogens with potential for systemic infection
  • Tetanus
  • Rabies
  • Bartonella (cat-scratch disease)
  • Leptospirosis
  • Brucellosis
  • Tularemia