See also

Snakebite
Spider bite – Big black spider
Spider bite – Redback spider
Management of tetanus prone wounds
Rabies and Australian Bat Lyssavirus post exposure prophylaxis

Key Points

1. Animal and human bite injuries in which the skin is broken pose a high risk of infection and are considered contaminated wounds; prompt thorough washout is required
2. Adequate analgesia/anaesthesia/sedation is important to facilitate washout and wound exploration
3. These wounds require a thorough assessment for depth and injury to associated structures
4. Most bite injuries should be left open, without primary closure

Background

• Children (particularly toddlers) are the most common victims of animal bites
• Dog bite wounds are most often crush injuries, lacerations and abrasions resulting from the high pressures generated from the canine jaw and the associated ripping and tearing motion
• Cats almost always inflict puncture wounds, which can appear small at the surface but can penetrate deeply and damage bone, joints and tendons
• Human bite injuries can be sustained from frank bites or clenched-fist injuries
• A clenched-fist injury occurs when a closed fist impacts the teeth of another person (eg resulting from a punch), also known as a “fight bite”
• Infection is the most common complication of bite injuries, especially cat and human bites
• Bite infections are polymicrobial, with potential pathogens arising from the mouth of the biting mammal, the child’s own skin flora and the environment
• There is risk of transmission of blood-borne viruses after human bites if blood exposure occurs

Assessment

History

• Animal or person involved
• Timing of injury
• Number and location of bites
• Risk of associated injuries eg if the child has fallen or been dragged
• Immunisation status (particularly tetanus)
• Other medical history: co-morbidities (eg immunosuppression), regular medications, allergies
• Social history: home environment, other household members, supervision around animals

Examination

• Location of injury
• Areas more likely to require specialist surgical involvement are face, hands, feet, genitals
• A clenched-fist injury involves laceration over the dorsum and MCP joints of the hand
• Associated injuries
• C-spine/head if fall has occurred
• Long bone/limb/spinal if child has been dragged
• Eye injury if face is involved
• Assess depth of wound (subcutaneous, breach of muscle fascia)
• Cat bites and clenched-fist injuries often penetrate deep tissues
• Look for evidence of neurovascular or tendon injury prior to local anaesthetic infiltration (altered sensation, haemorrhage, loss of function)
• If joint involved, examine the wound in a range of positions
• Assess viability/perfusion of skin edges of wound and skin distal to the injury
• If concerned about perfusion refer to plastic surgery for further exploration and assessment in theatre
• Assess for signs of infection (surrounding erythema, purulence, fever)
• Infection can be clinically evident in dog bites within 24 hours and in cat bites as quickly as 12 hours
• Consider child abuse if there is any suspicion that bite is from a human adult

Management

Any life-threatening injuries should be treated as per trauma guidelines (see Trauma- primary survey)

Children presenting with bite injuries should be fasted from arrival, in case they require sedation +/- surgical intervention

Investigations

Wound swabs:

• Cultures should not be taken for wounds that are not clinically infected, as there is poor correlation between early culture results and subsequent infections
• Collect wound swabs for MCS only where there is clinical evidence of infection

Imaging:

• Xray of the area may be indicated if there is suspicion of underlying bony injury, joint involvement or foreign body in wound
• Further imaging: seek senior advice
• Ultrasound: if suspected collection associated with an infected wound
• CT head: in children who have sustained a dog bite of uncertain depth to the scalp, or bite marks on opposing sides of the skull, a CT should be performed to evaluate for associated skull fracture or penetrating injury
• Abdominal CT: if abdominal injuries sustained

Treatment

Any bite injury which involves a “special location” (face, hand, foot or genitalia), or has extensive skin loss (>1cm defect present on attempts to oppose skin edges), requires referral to relevant surgical team for assessment and management

Washout

• All animal and human bite wounds with broken skin require washout and exploration with anaesthesia +/- sedation
• A consideration of available resources, time of day and appropriate staffing will determine the most appropriate setting for this to occur
• Remove any foreign bodies (teeth, debris)
• Irrigate the wound using 0.9% sodium chloride under pressure with a 20mL syringe and large-bore cannula
• Use enough fluid to remove all visible dirt and foreign material
• At least 250mL generally required
• Explore the wound and assess for extent/depth, potential injury to underlying structures (nerve, vessel, muscle, tendon) or extension into joint
• If any doubt regarding extent of wound or associated injuries, or concerns regarding ability to perform adequate washout or exploration in the Emergency Department, refer to specialty surgical unit (Plastics or Orthopaedics)

Wound closure and dressing

• Most animal and human bite wounds should be allowed to close by secondary intention (ie left open) 
• Primary closure may be considered in select wounds: low infection risk injuries which can be adequately explored and irrigated, are <12 hours old and where cosmesis is an issue ie face/neck
• Elevation of affected limb for 48-72 hours is recommended

Antibiotics
Antibiotic prophylaxis is recommended in clinically non-infected bite wounds with the following high-risk features

• Wounds undergoing primary closure
• Delayed presentation (wound > 8 hours old)
• Deep puncture wounds or lacerations
• Bite on hands (including clenched-fist injuries), face, feet or genital area
• Close proximity to bone or joint
• Associated crush injury
• Involving an open fracture
• Immunocompromised child
• Cat bites

Recommended oral prophylaxis:

Amoxicillin/clavulanate 22.5mg/kg (max 875mg) (amoxicillin component) oral BD for 5 days

In penicillin hypersensitivity:
Metronidazole 10mg/kg (max 400mg) oral BD for 5 days
PLUS
Trimethoprim-sulfamethoxazole 4/20mg/kg (max 160/800mg) oral BD for 5 days

If wound appears grossly contaminated or infected, or if admission is required for surgical washout and repair, IV antibiotics are recommended:

Amoxicillin/clavulanate 25mg/kg (max 1g) (amoxicillin component) IV 6-8 hourly
OR
Ceftriaxone 50mg/kg (max 1g) IV daily + oral metronidazole 10mg/kg (max 400mg) TDS
OR
Piperacillin-tazobactam 100mg/kg (max 4g) (piperacillin component) IV 8 hourly

Recommend minimum 14 days total antibiotic therapy for infected wounds

• Longer duration of therapy likely to be required for infections involving deeper tissues, bone or joint
• Consider Infectious Diseases consult for advice on duration of therapy and IV to oral switch

Tetanus prophylaxis
Animal and human bites are considered tetanus prone wounds. See Management of tetanus prone wounds

Rabies prophylaxis
All patients in whom there is a suspicion or high risk of bite from a bat should receive post-exposure prophylaxis to protect against Lyssaviruses (ie rabies and Australian bat lyssavirus), regardless of time since injury. Seek advice from Infectious Diseases team and local Public Health unit. See Rabies and Australian Bat Lyssavirus post exposure prophylaxis

Post-exposure prophylaxis for blood borne viruses
In human bite injuries with associated blood exposure, consider the need for post-exposure prophylaxis against blood borne viruses (eg hepatitis B, HIV). Suggest discussing with Infectious Diseases team

Consider consultation with local paediatric team when

Specialist surgical input is required:

• Animal bite injuries in special locations eg face, hand, foot, genitals
• Poor perfusion associated with the injury
• Cosmetic risk
• Extensive skin loss
• The appropriate surgical specialty (plastic surgery/general surgery/orthopaedics) will depend on location of injury and policy of the local hospital

Child abuse or neglect is suspected due to nature of injuries or circumstances surrounding injury. See Child abuse

Consider discussion with Infectious Diseases team for management of bites from exotic animals

Consider transfer when

Child requiring care beyond the level of comfort of the treating hospital

For emergency advice and paediatric or neonatal ICU transfers, see Retrieval Services

Consider discharge when

• Wound has been adequately irrigated and assessed with no evidence of associated injuries
• Oral antibiotics prescribed where indicated
• GP follow up for wound review can be arranged in 2-3 days
• Dangerous animals have been reported to local councils where required

Parent information

Raising Children Network - Dogs and Children: preventing child injuries

Last updated March 2023