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Animal bites

Author: Jenna Beaumont. Final year medical student, University of Auckland. Chief Editor: Dr Amanda Oakley, Dermatologist, Hamilton, New Zealand, May 2015.

Introduction

The majority of animal bites received by humans are dog bites (85–90%), followed by cat bites (5–10%) and rodent bites (2–3%).

Human bites constitute 2–3% of animal bites received by humans.

Dog bites

Most dog bites in young children occur on the head and neck. In older children and adults, they are more commonly situated on the arms and legs. This is likely due to the level of these body parts in relation to the mouths of large dogs.

Dog bites commonly result in crush injuries, but may also cause scratches, deep cuts, puncture wounds, and tearing of the skin and underlying flesh.

Cat bites

Most cat bites occur on the arms and the hands. Cat bites typically result in either scratches or deep puncture wounds.

Rodent bites

Complications of animal bites

Complications of animal bites include:

Animal bite wound infection

Wound infection can lead to:

Up to 20% of dog bite wounds become infected. Most dog bite wound infections are polymicrobial. The most common pathogens are:

Cat bite wounds are more likely to become infected than dog bite wounds, due to the tendency of cat bites to result in deep puncture wounds. Bites located on the hands have a greater risk of leading to further complications such as osteomyelitis or septic arthritis. The most common pathogens are:

Bartonella henselae, the causative agent of catscratch disease , can also be transmitted via a bite from an infected cat.

Approximately 20% of rodent bite wounds become infected. The most common pathogens are:

Bites from rodents infected with Streptobacillus moniliformis or Spirillum minus can result in rat bite fever, a rare systemic illness that can be serious or fatal if untreated. Patients with rat bite fever typically present 10 days to 4 weeks after a rodent bite with fever, rash, and septic arthritis.

Although New Zealand is free of rabies, the risk of an animal bite being infected with rabies must be considered if the bite occurred outside of New Zealand.

Initial management of animal bites

An animal bite wound should be carefully examined and treated as soon as possible after it has occurred to reduce the risk of complications.

When to see a doctor

If you have been bitten by an animal, consult a doctor:

Medical and surgical management of animal bite wounds

Assessment of the wound

Antibiotics for animal wounds

Antibiotic prophylaxis should be considered for high risk wounds, such as:

The most common bacteria cultured from animal wounds, Pasteurella, should be considered resistant to flucloxacillin, first generation cephalosporins, erythromycin, and clindamycin.

Amoxicillin clavulanate is the first-line antibiotic for animal wounds. Other options are:

Rat bite fever can be treated with penicillin or doxycycline.

Indications for hospital referral include:

A tetanus booster (tetanus toxoid) should be offered to patients if it has been more than 5 years since their last dose and they have completed their primary vaccination course. If they have not previously been fully immunised against tetanus, they should be offered tetanus toxoid plus tetanus immunoglobulin.

Rabies post-exposure prophylaxis should be considered for all bites that occurred overseas in a rabies endemic area.

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