Dog and cat bites

Assessment

Carefully examine bite wounds to identify deeper injuries, devitalised tissue, vascular injuries and retained foreign bodies, particularly for bites inflicted by animals with small teeth.

Assess for:

• infection
• neurovascular compromise (e.g. weakness, numbness or excessive bleeding)
• alteration in function (e.g. decreased range of motion)
• risk for wound infection
• tetanus.

Review the tetanus immunisation status of patients. Consider tetanus prophylaxis.

Increased risk of infection

Median time to signs and symptoms of infection:

• dog bite - approximately 24 hours
• cat bite - approximately 12 hours. Infections apparent within hours of a cat bite have been described.

Time elapsed between the bite and presentation for care, such as delayed presentations (≥12 hours after a bite on the extremities and ≥24 hours after a bite on the face), increases risk of infection.

Medical conditions that increase risk of infection include:

• immunocompromise (e.g. diabetes mellitus or asplenia
• liver disease (e.g. cirrhosis)
• alcohol use disorder
• foreign implants (e.g. prosthetic joints or vascular grafts)
• prior cellulitis or lymphatic or venous compromise in affected extremity.

Types of infection

• Cellulitis: Infection of deep dermis and subcutaneous fat. Symptoms include erythema, oedema, warmth, swelling, fever, with or without discharge.
• Skin abscess: Can be superficial or deep.
  • Superficial abscesses generally present as tender, fluctuant, erythematous nodules with surrounding cellulitis.
  • Deep abscesses present with pain, tenderness and induration without obvious fluctuance or skin erythema.
• Finger flexor tenosynovitis: This condition requires prompt recognition and surgical debridement because an infection of the finger flexor tendons can spread rapidly along the sheath compartments into the hand and forearm. Presents with tenderness along the flexor tendon, fusiform swelling, finger held in flexion at rest, tendon pain with passive extension.
• Septic arthritis or osteomyelitis: Occurs if bite penetrated bone or a joint space, or if soft tissue infection spreads to bone or joint.
  • Septic arthritis should be suspected in a patient with a joint effusion, warmth or pain with passive movement of an involved or adjacent joint.
  • Osteomyelitis is often challenging to diagnose and should be suspected if the bite was over a bone and pain, tenderness, erythema or swelling progress despite appropriate oral antibiotic therapy.
• Necrotising soft tissue infection (e.g. fasciitis): Limb and life threatening. Difficult to diagnose. Presents with rapidly progressive pain and oedema, pain not consistent with clinical findings, crepitus, sepsis or progressing infection despite wound care and antibiotics.

Management

Investigations

Image as required to rule out fractures and foreign bodies.

If superficial abscess or suspected deeper infection, consider point of care ultrasound, MRI or CT scan.

In children <3 years with a dog bite to the scalp associated with a wound of uncertain depth, CT of the head may be useful to evaluate for penetrating injury of the skull. CT findings may include skull fracture, puncture through the outer plate of the skull or free air in the cranial vault.

In patient with suspected infection obtain:

• wound gram stain and cultures
• blood cultures if suspected systemic infection.

Treatment

The recommended management of bites is:

• thorough cleaning
• irrigation
• debridement
• elevation
• immobilisation.

Wound preparation

• Control bleeding. Apply direct pressure to actively bleeding wounds.
• Clean wound with soap and water or an antiseptic solution.
• Irrigate with tap water or sterile saline and remove grossly visible debris, if present.
  • Cleaning the wound is often better tolerated in patients who present immediately after the bite compared with patients who have an infected wound.
• For patients with significant pain, local anaesthesia may be required to facilitate initial wound care.

UpToDate: Management of dog and cat bites (NSW Health login required)

Wound closure

For most patients with uninfected bite wounds, leave the wounds open to heal by secondary intention rather than by primary closure.

Primary closure is reasonable for a patient with a facial laceration (including a cat bite) that is sufficiently large to affect cosmesis or a gaping dog bite on the trunk, arm or leg (not on a hand or foot) who meets all of the following criteria:

• uninfected wound
• immunocompetent patient
• recent bite (<12 hours old for bites on an extremity, <24 hours old for facial bites)
• no crush injury or puncture wound
• no prior episode of cellulitis or venous or lymphatic compromise on the affected extremity.

For a wound that may benefit from primary closure but has one of these contraindications, consider prophylactic antibiotics with a plan for delayed primary closure after three to four days.

Unless the clinician has extensive experience with delayed primary closure, referral to a surgeon or other wound expert is advised since additional debridement (e.g. of excessive accumulated granulation tissue) may be necessary at the time of closure.

Indications for surgical consultation

Surgical consultation is warranted for:

• bites with associated fracture, joint disruption, retained foreign body or abnormal extensor tendon examination
• complex facial lacerations
• wounds on the hand or feet
• deep wounds, especially if significant avulsion or amputation is present
• wounds associated with neurovascular compromise.

Antibiotic therapy

Antibiotic therapy is required for infected bite injuries refer to the Therapeutic Guidelines Bite wound including clenched-fist injury (NSW Health login required).

For bites that are not infected, antibiotic therapy is usually not necessary for otherwise healthy individuals if the risk of wound infection is low. Give presumptive therapy if the risk of wound infection is high, including if any of these criteria apply:

• presentation to medical care is delayed by eight hours or more
• the wound is a puncture wound that cannot be debrided adequately
• the wound is on the hands, feet or face
• the wound involves deeper tissues (e.g. bones, joints, tendons)
• the wound involves an open fracture
• the patient is immunocompromised (e.g. due to asplenia or immunosuppressive medications) or has alcoholic liver disease or diabetes.

Background

The bacteria associated with animal bites are Pasteurella species, S. aureus, Capnocytophaga canimorsus, Streptococcus species and anaerobic bacteria.

Dog bites

Dog bites are associated with a range of injuries, from minor wounds (e.g. scratches or abrasions) to major wounds (e.g. gaping lacerations, deep puncture wounds, tissue avulsions and crush injuries). In particular, the jaws of large dogs, such as pit bull terriers, German shepherds and Rottweilers, can exert a strong force that may inflict serious injury and damage underlying structures.

Children are particularly vulnerable to dog attacks, due to their size and the proximity of their face to the dog's mouth, and attacks are frequently associated with interaction with the dog (possibly provocative) before the attack.

Cat bites

Cat bites tend to penetrate deeply with higher risk of deep infection (abscess, septic arthritis, osteomyelitis, tenosynovitis, bacteraemia or necrotising soft tissue infection) than dog bites. For example, in a retrospective series that included more than 2,500 dog bites and almost 1,000 cat bites, infection rates were 7 and 49 percent, respectively.

Patient information

Dog, cat and bat bites
Source: Healthdirect