animal bites in Australia

see also:

• toxins and envenomations
• insect bites and stings
• marine stings in Australia

• ~64% of Australian households have a pet
• ~50% of Australians will have an animal bite in their lifetime
• ~2% of Australians will be bitten in any one year with 1-2 dying from an animal bite (usually children bitten on head and neck)
• 85-90% of animal bites are dog bites, 5-10% are cat bites, 2-3% are human bites, 2-3% are rodents.
• ~100,000 will be injured from dog attacks each year with 13,000 seeking treatment in hospital
• children aged < 5yrs are at greatest risk of dog bites and are often bitten on the face, whereas adults tend to be bitten on upper limbs from freely roaming dogs.
• ~75% of dog bites are caused by 5 of the 160 available breeds even though they account for only 31% of the dog population:
  • German Shepherds, Pit Bull Terriers, Blue/Red Heelers, Dobermans and Rotweillers.
  • these breeds are 4-5x more likely to bite than other breeds but other factors contribute such as training and neutering.
• surveys have suggested that 50% feared dog attacks and 21% modified their behaviour towards dogs
• most cat bites occur in women and are often unprovoked.

• document fang penetration
• consider XRay to exclude fracture, bone penetration, animal tooth remnants
• explore wound to exclude involvement of deeper structures
• if wound is clinically infected, take cultures and specifically request:
  • aerobic and anaerobic cultures
  • fastidious organisms
  • extended incubation
  • common causal organisms:
    • dog bites (~18% become infected):
      • Pasteurella dagmatis, canis (50%)
      • Staph aureus/intermedius, Streptococcus sp, Moroxella sp, Neisseria sp
      • Capnocytophaga canimorsus (4.7%) - risk of severe sepsis in immunocompromised or asplenic patients
    • cat bites (28-80% become infected):
      • Pasteurella multocida (75%)
      • mixed aerobes and anaerobes
      • Bartonella henselae, the cause of cat-scratch fever can be transmitted by scratch or bite of infected cat (30% of cats) or cat flea.
    • rodents (10% become infected)
      • Streptobacillus moniliformis and Sprillum minus cause rat bite fever charcaterised by triad of fever, rash & arthritis and most respond well to Rx with penicillin or doxycycline
    • human bites
      • Strept viridans, Group A Strept, anaerobes, Eikenella, Hep B/C and rarely HIV / AIDS

• tetanus prophylaxis
  • as appropriate - see tetanus
• if Australian bat lyssavirus exposure
  • see rabies and related lyssaviruses
  • this is fatal without vaccination
• rabies prophylaxis if bitten in rabies-prone country
  • see rabies and related lyssaviruses
  • this is fatal without vaccination
• cleanse wound
  • use copious quantities of Normal saline or water
  • if possible rabies or it was a bat then also apply a virucidal agent such as betadine and allow to dry and ensure post-exposure vaccination for rabies
• consider primary wound closure if presentation < 10hours post-bite
  • controversial as risk of infection
  • if facial wounds then generally refer to plastics for opinion
  • if possible penetration into a joint then refer to orthopaedics for consideration of joint washout
• reduce swelling:
  • elevate limb
  • immobilise limb
• consider prophylactic antibiotics if high risk wound
  • controversial
  • metanalysis seems to show relative risk of infection is 0.56 (0.32-0.82 CI) with antibiotics with absolute benefit of 1 infection prevented per 14 treated (Cummings. Ann Em Med (1994) 23:535-40).
  • high risk wounds:
    • puncture or crush wound
    • hands, feet, face
    • penetration of underlying tissues (bone, joint, tendon sheaths (esp. puncture wounds on fingers), vascular)
    • prosthetic joint
    • delayed presentation > 8hr
    • immunocompromise
  • choice of antibiotic
    • amoxycillin + clavulanate bd for 5 days
• antibiotics if infection established:
  • metronidazole 10mg/kg up to 400mg o bd for 14 days, PLUS EITHER
    • cefotaxime or ceftriaxone 50mg/kg up to 1g iv daily for 14d, or,
    • if immediate penicillin HS, then:
      • doxycycline 200mg 1st dose then 100mg bd if age > 8yrs, or,
      • cotrimoxazole bd, or,
      • ciprofloxacin 10mg/kg up to 500mg o bd
  • alternatively, can use either:
    • piperacillin + tazobactam 8h for 14d, or
    • ticarcillin + clavulanate 6h for 14d
• consider hep B/C and HIV Mx if high risk human bites
• consider non-accidental injury if child with human bites and intercanine distance > 3cm

• patient education
  • warning signs of infection
  • prevention of bites
    • avoid purchasing dangerous breeds
    • sterilization of male dogs
    • dog training, particularly puppy socialisation
    • familiarising the dog to children
    • lead use
    • encourage children to approach dogs cautiously
    • don't leave young children alone with dogs
    • hand wash after handling animals +/- wear gloves
    • early wound cleaing after bites
    • immunise bat handlers
    • warn immunocompromised or asplenic patients to seek Rx early after any bite
• patient review in 24-48hr

• Dendle & Looke. Em Med. Aust. (2008) 20, 458-467.