Bites, Animal

Article Author:
Kenneth Maniscalco
Article Editor:
Mary Ann Edens
Updated:
11/15/2018 3:58:02 PM
PubMed Link:
Bites, Animal

Introduction

Animal bites account for approximately one percent of all ED visits in the U.S. yearly and range from superficial injuries to disfiguring and even fatal wounds.  Even relatively minor wounds have the capacity to become infected, and therefore all bites should be evaluated carefully and thoroughly with a mind to potential complications.  This chapter will focus on dog and cat bites and the common sequelae as they are the most prevalent, and when considered with human bites (which will be discussed in another chapter) account for over 95% of the total bite wounds seen in the ED. [1][2][3]

Etiology

Domesticated cats and dogs inflict practically all of the bites encountered in the ED in the United States.  The most common complication is local wound infection. Infections resulting from bites of all animal species are poly-microbial with aerobic and anaerobic bacteria; dogs and cats have an oral flora of Pasteurella, Staph, and Strep most commonly.  In cat bites and scratches, Bartonella infections are an additional concern.  Dog bites in immunocompromised individuals, especially asplenic patients, raise concern for a Capnocytophaga sepsis. [4]      

Epidemiology

Dog bites predominate (60-90%) followed by cat bites (5-20%).  Children are more commonly bitten on the head, face, and neck due to their proportionately larger heads and shorter stature while adults are more commonly bitten on the hands and arms.  Dog bites happen more in men and children.  The patient usually knows the dogs and the bites are less commonly provoked.  Cat bites are more common in women and adults, and the bites are more often provoked.  In less traumatic bites, especially cat bites due to the puncturing nature of cat teeth, the patient will commonly only present after the infection has become apparent and management has become more complicated.[5][1]

Pathophysiology

The initial injury is the result of the physical trauma of teeth puncturing and/or tearing soft tissue, and in the case of some dog bites, blunt force breaking bones. Dog bites are more commonly macerated due to the ripping and tearing forces involved.  Cat bites are narrow and deep as the animal rarely pulls or shakes its head, simply biting and holding.  Because the cat bite wound is deep and narrow, it is much more likely to seal itself relatively quickly, providing an anaerobic environment for the inoculated bacteria as well as initially appearing less consequential and prolonging time to seeking medical care.  

History and Physical

Focused H&P should determine the circumstances surrounding the bite, location of the bite, type of animal, time of occurrence, whether the patient has been febrile, local erythema, swelling, warmth, or purulent drainage.  If the patient is stable, the wound should be thoroughly explored after local or regional anesthesia to determine the potential for damage to underlying structures and foreign body inoculation. Local and distal neurovascular status should be assessed after anesthesia as well as pain and apprehension may affect patient compliance with the exam.  Pertinent history includes any immunosuppression, be it iatrogenic (transplant, rheumatic disease treatment) or from a disease process (diabetes, HIV/AIDS, sickle cell disease.).     

Evaluation

As with all traumas, the initial evaluation is to ensure airway, breathing, and circulation is intact.  Active venous bleeding should be controlled with direct pressure while arterial bleeding will typically necessitate consult services.  The wound should be explored for foreign bodies such as broken teeth, claws, dirt, and plant material.  When exploring the wound underlying structures should be examined for potential damage as well.  During exploration, the patient should range the underlying structures through a full range of motion to ensure that injuries to those underlying structures are not missed.  [2]

Treatment / Management

All wounds should be extensively irrigated and the patient’s tetanus status updated if necessary.  Provide appropriate pain management before exploration, irrigation, or debridement of the wounds.  The patient’s TDaP status should be updated if necessary.  For uncomplicated dog bites, the patient should be educated on the risk/benefit of closure versus healing by secondary intention and the decision made with the provider.  If the patient presents delayed from the initial bite the risks of closing the wound almost certainly outweigh the cosmetic benefits of closure.  If the wound is closed, the patient should be discharged with a week’s course of amoxicillin-clavulanate.  Complicated dog bites should be stabilized and referred to the appropriate consult service.  Cat bites deeper than superficial should be irrigated thoroughly under local anesthesia and the wound left open.  The patient should be discharged with a week’s course of amoxicillin-clavulanate and given strict wound care precautions.  All bites to the hands or feet, bites in immunocompromised individuals, bites which already show signs of infection, and bites which have a puncture characteristic should be treated with amoxicillin-clavulanate.  For patients with penicillin allergies, second-line therapy is doxycycline or TMP-SMX plus metronidazole or clindamycin.  Patients with extensive local infection should be seen by the appropriate consult service, patients with evidence of disseminated infection should be treated with broad-spectrum IV antibiotics and admitted for further care.[6][7][8]

Prognosis

The prognosis for most animal bites is excellent. However, it is important to know that on average about 30-50 people die from dog bites each year.

Complications

  • Cellulitis
  • Tenosynovitis
  • Endocarditis
  • Osteomyelitis
  • Abscess
  • Meningitis
  • Tendon rupture
  • Nerve injury
  • PTSD
  • Rabies

Postoperative and Rehabilitation Care

Patients with animal bites need to be seen within 48-72 hours after initial treatment to ensure that they are not developing an infection. The animal should be removed from the home and placed in a different location.

Deterrence and Patient Education

Patients should be encouraged to be updated with tetanus vaccination.

Pearls and Other Issues

  1. Rabies is rarely a concern due to the broad vaccination program in domesticated animals and the fact that the patient usually knows the animal. Depending on the local prevalence of the disease you may be able to defer rabies prophylaxis for dog and cat bites. 
  2. If the status of the animal is unknown rabies prophylaxis may be deferred if the animal is in custody and may be observed or has been dissected for evaluation of rabies.  Most commonly rabies is found in bat and skunk populations. 
  3. Any bite or suspected bite from a bat should be treated with rabies prophylaxis.  Rabies prophylaxis initiation in the ED requires the rabies vaccine provided in a distant site from the injury with as much of the required rabies immune globulin being given local to the wound. 
  4. Further rabies vaccine doses should be given on days three, seven, and fourteen. 
  5. Immunocompromised individuals with cat bites or scratches should be covered with TMP-SMX, ciprofloxacin, or rifampin as prophylaxis against cat-scratch disease.
  6. Sepsis from Capnocytophaga is covered by standard prophylaxis in dog bites in immunocompromised individuals. 
  7. Bites from K-9 officers should be treated similarly as the above with the additional documentation that the officers will require. 

Enhancing Healthcare Team Outcomes

About 300,000 people with dog bites visit the emergency room or the primary care provider each year. The earlier the treatment, the better the outcome. Managing animal bites requires a multidisciplinary approach as the bite may occur on any part of the body. There should be no hesitancy in consulting with the appropriate specialist if the bite is on the eyes, nose, hands, genitals or the scalp. Several guidelines exist on managing specific animal bites like the dog, cat, snake, scorpion, bees, ants or other wildlife. Healthcare workers who manage animal bites should be aware of the latest guidelines and be aware of the organisms and the antibiotics needed to manage such injuries. Since many animal bites are seen by the primary care provider or the emergency room, the first treatment is to ensure that the wound is irrigated and cleaned. Debridement of necrotic or dead tissue is the next step. If there is any doubt in the management, the injury is severe or to the hand, a consult should be made with a specialist. for example, serious injury from dog bites should always be managed by an interprofessional group of healthcare professionals [9][10] (Level lll).

Outcomes and Evidence

The majority of people with animal bites have an excellent outcome. However, injuries to the face, groin and hands can lead to high morbidity. The available literature reveals conflicting opinions on management and until evidence-based medical evidence is available, the treatment will remain empirical. [11](Level V)