animal bites

Last edited 02/2023 and last reviewed 11/2023

Animal bites are usually from dogs and cats in the United Kingdom. Typically, the hand is injuried during a defensive motion. The history is usually obvious; clinically there is cellulitis with associated lymphangitis. Osteomyelitis, tendon and joint injury also may occur.

The organisms involved is much the same as for human bites e.g. mixed anaerobes, streptococci. However, the Gram-negative coccus Pasteurella multocida is also common. The likelihood of rabies should be assessed in the history.

• most infections from animal bites are polymicrobial and contain both aerobic and anaerobic organisms. Causative organisms for infections from cat and dog bites (the most common animal bites) include Pasteurella, Streptococcus, Staphylococcus, Neisseria, Corynebacterium, Fusobacterium nucleatum and Bacteroides (1)

Any penetrating injury should be explored. Wound excision, irrigation and delayed closure may all be necessary. Treatment with antibiotics is mandatory. Radiography for foreign bodies may prove useful: all should be removed. Tetanus prophylaxis should be given. The hand should be splinted and elevated.

Is antibiotic prophylaxis indicated for dog bites? (1)

• antibiotic prophylaxis should be offered for a dog bite (or a bite from another traditional pet) if it:
• has broken the skin and penetrated bone, joint, tendon or vascular structures or
• is deep, a puncture or crush wound, or has caused significant tissue damage or
• is visibly contaminated (for example, if there is dirt or a tooth in the wound)
  
  
• antibiotic prophylaxis could be considered for a dog bite (or a bite from another traditional pet other than a cat) that has broken the skin and drawn blood if it involves a high-risk area or is in a person at risk of a serious wound infection because of a comorbidity
  
• antibiotic prophylaxis is not needed for a dog bite (or a bite from another traditional pet) that has not broken the skin, or has only caused a superficial wound that has broken the skin but not drawn blood

General wound closure considerations (2)

• small wounds
  • may be left open to heal by secondary intention with daily non-stick dressing changes until the skin has re-epithelialised
• gaping wounds
  • can be approximated and closed after copious irrigation and debridement
• wounds to the face from any animal
  • can be closed (for cosmesis; the face has no higher risk of infection than elsewhere)
• feline (cat) bite
  • should avoid closing all non-facial wounds
• canine (dog) bites
  • majority can be closed except in the hands or feet, where infection risk is much higher
• human bites
  • should avoid closing non-facial wounds or facial wounds more than 24 hours after injury
  • requires follow up with a plastic surgeon
• puncture wounds
  • have an especially high risk of infection
  • should let all puncture wounds heal by secondary intention (after irrigation)

Risk of infection associated with mammalian bite (2)

• 2% to 25% of dog bites,
• 30% to 50% of cat bites
• up to half (47%) of human bites - which increases with delay to presentation and size of wound

Reference:

• NICE (November 2020). Human and animal bites: antimicrobial prescribing
• Colmers-Gray I N, Tulloch J S, Dostaler G, Bai A D. Management of mammalian bites BMJ 2023; 380 :e071921 doi:10.1136/bmj-2022-071921