Description

A bite to the human skin and/or subcutaneous tissues by another mammal causing local, and in some cases systemic, effects

Epidemiology

• Animal bites
  • Approximate frequency
    • Dogs: 80–90%
    • Cats: 5–15%
    • Rodents or rabbits: 1%
    • Raccoons and other animals: 1%
  • The offending animals are often well known to the victim.
  • Children are the most common victims:
    • Boys are more likely than girls to be bitten by dogs.
    • Girls are more likely to be bitten by cats.
• Human bites
  • Third most common cause of all bites seen in ED
  • Younger children more often present with occlusion bites (which generally compress tissue causing ecchymoses).
  • Children >10 years old are more likely to present due to accidental injury during sports activities or intentionally during altercations or abusive situations. These are more likely to be due to clenched fist/fight bites (puncture wounds when fist hits teeth).

General Prevention

• Ensure that children receive routine immunizations against tetanus and hepatitis and that family pets are immunized against rabies.
• Never leave small children alone with pets.
• Encourage children to avoid contact with wild animals and dead animals.

Pathophysiology

• Injury associated with bite types:
  • Dog
    • Younger children more often have head and neck bites; older children more often extremities are affected.
    • Crush and tear injuries
    • May involve bone
  • Cat
    • Puncture-type wounds
    • Penetrate deeper and carry a higher risk of infection (think osteomyelitis, septic arthritis)
  • Human
    • Generally only violate skin
    • However, clenched fist/fight bites tend to be worse due to the possibility of penetrating injury.
    • Penetration into joint and tendon sheath spaces can occur (especially bites overlying the metacarpal-phalangeal areas).
• Infection
  • Animal bites are considered grossly contaminated.
  • Infections are most commonly polymicrobial with both aerobic and anaerobic organisms.
  • Infected dog and cat bites
    • Pasteurella species are the most frequent isolates.
    • Dog: Pasteurella canis, new emerging bacteria Capnocytophaga species (can cause endocarditis, meningitis, sepsis)
    • Cat: Pasteurella multocida and Pasteurella septica
    • Common anaerobes include Fusobacterium, bacteroides, Porphyromonas, and Prevotella.
  • Infected human bites
    • Streptococcus anginosus
    • Staphylococcus aureus
    • Eikenella corrodens
    • Fusobacterium species
    • Prevotella species

History

• Animal bites
  • Type of animal
  • Apparent health of the animal
  • Provocation for the attack
  • Timing of the bite
  • Location of the bite or bites
  • Availability of animal for undergoing observation (i.e., known animal as opposed to a stray or wild animal)
  • Rabies immunization status of the animal
• Past medical history
  • Tetanus immunization status of the child
  • Hepatitis B immunization status of child
  • Is patient immunocompromised or asplenic?

Physical Exam

• Carefully assess neurovascular integrity.
• Location of bite
  • If bite is located over a joint, assess for violation of joint capsule.
• Examine entire patient to ensure that all wounds are identified and treated.
• Older wounds
  • Assess for signs of infection such as erythema, induration, purulence, regional adenopathy, and elevated temperature.

Diagnostic Tests and Interpretation

General Measures

• Wound care:
  • Copious irrigation with normal saline or tap water to remove visible debris
  • Do not use antimicrobial solutions to irrigate.
  • Cleanse but do not irrigate puncture wounds.
• Human bites over metacarpals (clenched-fist injuries) require orthopedic evaluation for possible surgical exploration and irrigation.
• Debride devitalized tissue.
• The increased risk of infection associated with suturing a potentially contaminated wound must be weighed against the cosmetic effect due to nonclosure:
  • Primary closure of larger wounds or significant facial wounds may be indicated unless wound is old or has evidence of infection.
• Hand wounds may be an exception, due to high propensity for infection.
• Avoid tissue adhesives for wound closure.

Medication (Drugs)

• Antibiotics: Data are often contradictory. In general, treat all high-risk individuals or bites requiring closure and consider in average risk individuals (see “Alert” section).
  • Amoxicillin–clavulanic acid PO is drug of choice (50 mg amoxicillin/kg/24 h divided b.i.d. or t.i.d. for 5 days).
  • An alternative antibiotic regimen for penicillin-allergic patients is trimethoprim–sulfamethoxazole plus clindamycin.
  • Infected wounds should be treated for at least 10 days.
• IV antibiotics and hospitalization should be considered for patients with signs of systemic involvement or infected-appearing wounds to face and hands.
  • Ampicillin/sulbactam IV 150 mg ampicillin/kg/24 h in 4 divided doses
  • For penicillin-allergic patients, 3rd-generation cephalosporin
• Tetanus prophylaxis if indicated
• Rabies prophylaxis if indicated
  • Unknown dog or cat; dogs or cats with unknown immunization status that cannot be observed for 10 days
  • Bites from wild animals, including raccoons, bats, skunks, foxes, coyotes
  • Because bat bites may go undetected, especially by a sleeping child, rabies prophylaxis is recommended after exposure to bats in a confined setting.
  • Rabies is unlikely if the child was bitten by an immunized dog, cat, or other pet (e.g., hamsters, guinea pigs, gerbils).
  • Rabies is unlikely if the child was bitten by a small rodent (squirrels, mice, or rats) or rabbit.
  • The regimen for patients who have not been vaccinated previously should include both human rabies vaccine (a series of 4 doses administered IM on days 0, 3, 7, and 14; immunocompromised patients should receive a fifth dose on day 28) and rabies-immune globulin (20 IU/kg) administered as much as possible into the wound, the remainder given IM at a site distant from the site used for vaccine administration.
• HIV postexposure prophylaxis (PEP)
  • There are case reports describing transmission of HIV by human bites; however, the risk of transmission due to biting is unknown. It is estimated to be extremely small. Bites with saliva containing no visible blood have no associated risk for transmission and, therefore, are not considered exposures.
  • HIV PEP requires a multidrug regimen administered over 28 days that can be associated with significant toxicity.
  • Decisions to initiate PEP are best made in consultation with local experts or by contacting the National Clinicians Post-Exposure Prophylaxis hotline at 888-448-4911.
  • Hepatitis B has been transmitted from nonbloody saliva. Check the vaccination status of the bitten (or biter if necessary) to consider PEP. Unvaccinated children should begin the hepatitis B vaccine series.
  • The transmission rate of hepatitis C via human bites is unknown, and no regimen for PEP currently exists.

Issue for Referral

• Human bites over metacarpals (clenched-fist injuries) require orthopedic evaluation for possible surgical exploration and irrigation.
• Local regulations dictate the reporting of animal bites to health departments.

Follow-Up Recommendations

Prognosis

Most injury from animal bites is trivial, but infections, and rarely deaths, do occur.

Complications

Human bites over metacarpals (clenched fist) can penetrate tendon sheaths, become infected, and result in a tenosynovitis.

ICD-9

• 882.0 Open wound of hand except finger(s) alone, without mention of complication
• 873.40 Open wound of face, unspecified site, without mention of complication
• 883.0 Open wound of finger(s), without mention of complication
• 027.2 Pasteurellosis
• V01.5 Contact with or exposure to rabies

ICD-10

• S61.459A Open bite of unspecified hand, initial encounter
• S01.85XA Open bite of other part of head, initial encounter
• S61.259A Open bite of unsp finger without damage to nail, init encntr
• A28.0 Pasteurellosis
• Z20.3 Contact with and (suspected) exposure to rabies

SNOMED

• 283683002 Mammal bite wound (disorder)
• 283792007 Animal bite of face (disorder)
• 283782004 Cat bite - wound (disorder)
• 283734005 Dog bite - wound (disorder)
• 262555007 Human bite - wound (disorder)
• 83172007 Pasteurella infection (disorder)
• 283738008 Dog bite of face (disorder)
• 283687001 Human bite of face (disorder)
• 283754006 Dog bite of hand (disorder)
• 444459008 Exposure to Rabies virus (event)
• 283705004 Human bite of hand (disorder)