DESCRIPTION

• Most bites are from provoked animals.
• Dog bite wounds:
  • Large dogs inflict the most serious wounds (pit bulls cause the most human fatalities).
  • Most fatalities in children (70%) due to bites to face/neck
  • Dogs of family or friends account for most bites.
• Cat bite wounds:
  • Majority from pets known to victim
  • 50% infection rate in those seeking care
  • Puncture wounds most frequent due to sharp thin teeth causing deep inoculation of bacteria
• Catscratch disease (CSD):
  • 3 of the following 4 criteria:
    • Cat contact, with presence of scratch or inoculation lesion of the skin, eye, or mucous membrane
    • Positive CSD skin test result
    • Characteristic lymph node histopathology
    • Negative results of lab studies for other causes of lymphadenopathy
• Rat bite wounds:
  • Occur in lab personnel or children of low socioeconomic class
  • Rat-bite fever (RBF), rare in US but high mortality rate
  • Rat bites rarely transmit rabies, and prophylaxis not routine

ETIOLOGY

• Dog and cat bites:
  • Pasteurella multocida is the major organism in both:
    • Twice as likely to be found in cat bites than dog bites
    • Gram-negative aerobe found in up to 80% of cat infections
    • Infection appears in < 24 hr
  • Staphylococcus or Streptococcus:
    • Infection appears in > 24 hr
  • Other organisms include anaerobes and Capnocytophaga canimorsus (dogs).
• Catscratch disease:
  • Caused by Bartonella henselae
• Rat bites:
  • Caused by Spirillum minus and Streptobacillus moniliformis (RBF)

[Outline]

• DESCRIPTION
• ETIOLOGY

SIGNS AND SYMPTOMS

• Distribution of mammalian bites:
  • Dog bites represent 80–90% of all bites.
  • Cat bites represent 5–15% of all bites.
  • Human bites represent 2–5% of all bites (see "Human Bite" chapter).
  • Rat bites represent 2–3% of all bites.
• Dog bites:
  • Appearance:
    • Crush injuries (most common), tears, avulsions, punctures, and scratches
  • Low rates of infection compared with cat and human bites
  • Infections usually present with:
    • cellulitis
    • malodorous gray discharge
    • fever
    • lymphadenopathy
• Cat bites:
  • Appearance:
    • Puncture wounds (most common)
    • Abrasions
    • Lacerations
  • High infection rates (30–50%) due to deeper puncture wounds
• Catscratch disease:
  • From the bite/scratch of a cat, dog, or monkey
  • Small macule or vesicle that progresses to a papule:
    • Begins several days (3–10) after inoculation
    • Resolves within several days or weeks
    • Regional lymphadenopathy occurs 3 wk postinoculation
    • Tender
    • Nonsuppurative
    • Resolves after 2–4 mo
  • Low-grade fever, malaise, headache
• Rat-bite fever:
  • Does not have to involve a bite. Can occur from handling of rats
  • S. moniliformis:
    • Begins several days (2–10) after exposure
    • Common in US
    • Fever, rigors, migratory polyarthralgias, headaches, nausea, and vomiting
  • S. minus
    • Incubation period from 1–3 wk
    • More common in Asia
    • Arthritis not common

History

• Animal's behavior, provocation, location, ownership
• Time since attack
• Past medical history: Conditions compromising immune function, allergies, and tetanus status

Physical Exam

• Record the location and extent of all injuries.
• Document any swelling, crush injuries, or devitalized tissue.
• Note the range of motion of affected areas.
• Note the status of tendon and nerve function.
• Document any signs of infection, including regional adenopathy.
• Document any joint or bone involvement.

DIAGNOSIS TESTS & INTERPRETATION

Lab

• Aerobic and anaerobic cultures from any infected bite wound
• Cultures not routinely indicated if wounds not clinically infected
• Catscratch disease:
  • Presence of elevated titers of B. (Rochalimaea) henselae, or
  • Positive reaction to catscratch antigen (CSA):
    • Inject 0.1 mL CSA IM
    • Induration at the site 48–72 hr later equal to or exceeding 5 mm is positive

Imaging

Plain radiograph indications:

• Fracture
• Suspect foreign body (e.g., tooth)
• Baseline film if a bone or joint space has been violated in evaluating for osteomyelitis
• For infection in proximity to a bone or joint space

DIFFERENTIAL DIAGNOSIS

• Human bite injuries: Human teeth cause crush injuries and animal teeth cause more punctures and lacerations.
• Bite injuries from other animals
• CSD-caused lymphadenopathy:
  • Reactive hyperplasia (leading cause of lymphadenopathy in children < 16 yr)
  • Infection, chronic lymphadenitis, drug reaction, malignancy, and congenital conditions

[Outline]

• SIGNS AND SYMPTOMS
• DIAGNOSIS TESTS & INTERPRETATION
• DIFFERENTIAL DIAGNOSIS

PRE-HOSPITAL

Apply pressure to any bleeding wound

INITIAL STABILIZATION/THERAPY

• Achieve hemostasis on any bleeding wound.
• Airway stabilization if bite located on face or neck

ED TREATMENT/PROCEDURES

• Wound irrigation:
  • Copious volumes of normal saline irrigation with an 18G plastic catheter tip aimed in the direction of the puncture.
  • Avoid injection of saline through tissue planes due to force of irrigation.
• Débridement:
  • Remove foreign material, necrotic skin tags, or devitalized tissues.
  • Do not débride puncture wounds.
  • Remove any eschar present so underlying pus may be expressed and irrigated.
• Wound closure:
  • Closing wounds increases risk of infection and must be balanced with scar formation and effect of leaving wound open to heal secondarily.
  • Do not suture infected wounds or wounds > 24 hr after injury.
  • Repair of wounds > 8 hr: Controversial
  • Close facial wounds (warn patient of high risk of infection).
  • Infected wounds, those presenting > 24 hr after the event, and deep hand wounds should be left open.
  • May approximate the wound edges with Steri-Strips and perform a delayed primary closure.
• Antibiotic indications:
  • Infected wounds
  • Cat bites
  • Hand injuries
  • Severe wounds with crush injury
  • Puncture wounds
  • Full-thickness puncture of hand, face, or lower extremity
  • Wounds requiring surgical débridement
  • Wounds involving joints, tendons, ligaments, or fractures
  • Immunocompromised patients
  • Wounds presenting > 8 hr after the event
• Elevate injured extremity
• Tetanus prophylaxis
• Rabies immunoprophylaxis:
  • Not required if rabies not known or suspected
  • Rodents (squirrels, hamsters, rats, mice) and rabbits rarely transmit the disease.
  • Skunks, raccoons, bats, and foxes represent the major reservoir for rabies.
  • See "Rabies" chapter for treatment guidelines.
• Catscratch disease:
  • Analgesics
  • Apply local heat to affected nodes.
  • Avoid lymph node trauma.
  • Disease usually self-limiting
  • Antibiotics controversial, consider if severe disease is present or immunocompromised victim
• Rat-bite fever:
  • High mortality (10%)
  • IV penicillin or doxycycline

MEDICATION

First Line

• Amoxicillin/clavulanic acid (Augmentin): 500/125 mg (peds: 40 mg/kg/24h) q8h PO
• Ampicillin–sulbactam (Unasyn): 3 g q6h IV
• Penicillin 1–2 million units q6h IV (peds 20,000–50,000 U/kg/d div. q4h IV)
• Piperacillin–Tazobactam (Zosyn): 4.5 g q8h IV
• Ticarcillin–clavulanate (Timentin): 3.1 g q4h IV
• Ceftriaxone (Rocephin): 1 g/d plus Metronidazole (Flagyl): 500 mg q8h

Second Line

• 2 drug therapy: 1 of the following below + anaerobic coverage:
  • Trimethoprim–sulfamethoxazole (Septra DS): 1 tablet q12h (peds: 8 mg/kg trimethoprim and 40 mg/kg sulfamethoxazole per day divided into 2 daily doses) PO
  • Penicillin (Penicillin VK): 500 mg (peds: 50 mg/kg/24h) PO q6h
  • Ciprofloxacin (Cipro): 500–750 mg q12h PO or 400 mg q12h IV
  • Doxycycline: 100 mg PO BID
• + (anaerobic coverage):
  • Clindamycin (Cleocin): 150–450 mg (peds: 8–20 mg/kg/24h) PO q6h or 600–900 mg (peds: 20–40 mg/kg/24h) IV q8h
  • Metronidazole (Flagyl): 500 mg PO TID (peds: 10 mg/kg/dose TID)

[Outline]

• PRE-HOSPITAL
• INITIAL STABILIZATION/THERAPY
• ED TREATMENT/PROCEDURES
• MEDICATION

DISPOSITION

Admission Criteria

• All bites:
  • Infected wounds at presentation
  • Severe/advancing cellulitis/lymphangitis
  • Signs of systemic infection
  • Infected wounds that have failed to respond to outpatient (PO) antibiotics
• Catscratch disease:
  • Prolonged fever, systemic symptoms, and/or marked lymphadenopathy

Discharge Criteria

• Healthy patient with localized wound infection:
  • Discharge on antibiotics with 24-hr follow-up.
• Noninfected wounds:
  • 48-hr follow-up

FOLLOW-UP RECOMMENDATIONS

• Hand specialist referral/follow-up for infected hand wounds.
• Healthy patient with localized wound infection: Discharge on antibiotics with 24-hr follow-up.
• 48-hr follow-up for noninfected wounds

[Outline]

• DISPOSITION
• FOLLOW-UP RECOMMENDATIONS

Animal bites must be reported to authorities in many localities.

ICD9

• 873.40 Open wound of face, unspecified site, without mention of complication
• 874.8 Open wound of other and unspecified parts of neck, without mention of complication
• 882.0 Open wound of hand except finger(s) alone, without mention of complication

ICD10

• S01.80XA Unspecified open wound of other part of head, init encntr
• S11.90XA Unsp open wound of unspecified part of neck, init encntr
• S61.409A Unspecified open wound of unspecified hand, init encntr

[Outline]

• ICD9
• ICD10

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• Brook I. Microbiology and management of human and animal bite wound infections. Prim Care. 2003;30(1):25–39.
• Elliott SP. Rat bite fever and Streptobacillus moniliformis. Clin Microbiol Rev. 2007;20:13–22.
• Galloway RE. Mammalian bites. J Emerg Med. 1998;6:325–331.
• Griego RD, Rosen T, Orengo IF, et al. Dog, cat, and human bites: A review. J Am Acad Dermatol. 1995;33:1019–1029.
• Klein JD. Cat scratch disease. Pediatr Rev. 1994;15(9):348–353.
• Pickering L. Red Book: 2003 Report of the Committee on Infectious Diseases. 26th ed. Elk Grove Village, IL: American Academy of Pediatrics; 2003.
• Smith PF, Meadowcroft AM, May DB. Treating mammalian bite wounds. J Clin Pharm Ther. 2000;25:85–99.
• Trucksis M. Rat-bite fever. UpToDate. May 6, 2011.

See Also (Topic, Algorithm, Electronic Media Element)

Rabies

Daniel T. Wu