Animal bites account for 1% of all visits to emergency rooms in the United States.
Two to five million animal bites occur every year.
More than 1 million victims of animal bites visit their physician at a total cost of approximately $30 million per year.
Animal bites result in 10 to 20 deaths every year in the United States, mainly among infants and small children.
Animal bites involving joints or bones are more likely to get complicated by septic arthritis, tenosynovitis, or local abscesses.
Bites to the hand require careful radiographic and surgical evaluation if a puncture or a severe laceration has been noticed.
Most casualties from animal bites are due to dog bites.
Note that human bites and cat bites account for the majority of infected wounds by clinicians.
Initial steps include the use of ice, elevation, and control of any bleeding.
Washing the wound with soap and water as soon as possible will help decrease the risk of rabies infection if done within 3 hours.
Note the circumstances of the bite attack, focusing on the behavior of the biting animal and whether the animal is in captivity and has been immunized against rabies.
Assess tetanus immunization status and allergies to antibiotics.
Provide good wound care in the form of adequate irrigation and debridement of nonviable tissue as needed.
General wound management measures such as rabies vaccine, tetanus toxoid administration, and wound closure should also be employed (see Table 41-1).
Specific inquiry should be made about risks for poor wound healing (see Table 41-2):
Diabetes
Peripheral vascular disease
Steroid use, splenectomy, or alcoholism
Table 41-1 Initial Evaluation and Management of Animal Bites
History
Physical Examination
Wound Care
Imaging
Indication for Hospitalization
Reporting
An exact history should be elicited and should include the type of animal that attacked the patient, whether the bite was provoked or unprovoked, and the circumstances in which the bite occurred.
If animal can be rabid, locate the animal for 10 days’ observation or sacrifice.
Obtain general health and immunization status of animal.
Record a diagram of the wound with the location, type, and depth of injury; range of motion; possibility of joint penetration; presence of edema or crush injury; nerve and tendon function; signs of infection; and odor of exudate.
Photo documentation may be useful in case that may involve litigation such as unleashed dog bite.
Obtain Gram stain, and wound cultures should be done in the presence of abscesses, sepsis, serious cellulitis, devitalized tissue, or foul odor of the exudate.
Animal bite wounds should be irrigated with copious amounts of normal saline.
Puncture wounds should be irrigated with a “high-pressure jet” from a 20-50 mL syringe and an 18-20 gauge needle.
Irrigation with either normal saline or Ringer’s lactate can decreased infection rate by 20-fold.
X-rays should be obtained if fracture bone penetration or foreign bodies are suspected
Fever, sepsis, spreading cellulitis, significant edema or crush injury, loss of function, compromised host, and patient noncompliance.
Require the reporting of bites by any animals known to be potential carriers of rabies, such as bats, raccoons, skunks, foxes, and cattle, to prevent cases of human rabies and control the spread of rabies within the animal community.
Document the time and location of the attack.
Debridement
Necrotic skin tags or devitalized tissues should be debrided and any foreign bodies should be removed
Obtain patient’s medical history such as splenectomy, steroid use, lung disease, peripheral vascular disease, diabetes, mastectomy, liver disease, and immunosuppression.
Wound closure: may be necessary for selected, fresh, uninfected wounds, especially facial wounds, but primary wound closure is not usually indicated.
Wound edges should be approximated with adhesive strips in selected cases
Table 41-2 Risk Factors in Bite Wound Infections
Factor
High Risk
Low Risk
Animal
Cat
Human
Pig
Dog
Rodent
Site of wound
Hand
Leg
Oral through and through
Joint
Face
Scalp
Mucosa
Type of wound
Puncture wound
Contaminated
Crush
Old
Large
Superficial
Clean
Recent
Co-morbidity
Diabetes mellitus
History of splenectomy
Peripheral vascular disease
Prosthetic heart valve
Use of corticosteroids and Cytotoxic drugs.
Alcoholism
Wounds inflicted on the hands and below the knee are the highest sites for infection risk. A dog bite to the hand may lead to infection 30% of the time as opposed to only 9% if bitten elsewhere. Hand injuries from cat bites have a nearly 20% infection rate.
In contrast, dog bites of the face and neck have an infection rate of only 0% to 5% even when sutured, unless they are severe and require hospitalization.
Patients with underlying medical conditions such as diabetes, peripheral vascular disease, splenectomy, liver disease, use of steroids, and an immunocompromised status have increased risk of infection and poor outcomes (Table 41-2).
Antibiotic prophylaxis is considered reasonable if the risk of infection is 5% to 10%.
Prophylactic antibiotics are not indicated for most routine dog bite wounds, except for hand wounds.
Because cat bites have been reported to have a high likelihood of infection, and infected cat bites often require hospitalization, it is not unwise to consider prophylactic antibiotics for cat bites, especially hand wounds (Table 41-3)
For dog bite wound infections, coverage of Pasteurella multocida must be used.
A second- or third-generation cephalosporin or amoxicillin-clavulanate is an excellent first-line agent.
Clindamycin plus sulfamethoxazole can be used for the patient having history of penicillin allergy.
Table 41-3 Antimicrobial Therapy: Indications for Prophylactic Antibiotics
Presentation more than 8 hours after bites?
Moderate or severe injury?
Cat bites (most)
Diabetes mellitus
Asplenic patient
Immunocompromised patient (mastectomy, liver disease, or steroid therapy)
Hand or facial involvement
Deep puncture wounds with possible bone or joint penetration
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