Basics
Description
Injury to the human skin and/or subcutaneous tissues caused by bite, causing local, and in some cases systemic, effects ‚
Epidemiology
- Animal bites
- Approximate frequency
- Dogs: 90 " “95%
- Cats: 3 " “8%
- Rodents or rabbits: 1%
- Raccoons and other animals: 1%
- 90% of the offending animals are well-known to the victim.
- Children are the most common victims:
- Boys are twice as likely as girls to be bitten by dogs.
- Girls are more likely to be bitten by cats.
- Human bites
- Most common in children ages 2 " “5 years
- In older children, bites may occur accidentally during sports activities or intentionally during altercations or abusive situations.
Incidence
- An estimated 4.5 million dog bites and 400,000 cat bites occur annually in the United States.
- The incidence of human bites is unknown due to underreporting.
General Prevention
- Ensure that children receive routine immunizations against tetanus and hepatitis and that family pets are immunized against rabies.
- Encourage children to avoid contact with wild animals and dead animals.
Pathophysiology
- Injury associated with bite types:
- Dog
- Crush and tear injuries
- May involve bone
- Cat
- Puncture-type wounds
- Penetrate deeper and carry a higher risk of infection
- Human
- Generally only violate skin
- However, penetration into joint and tendon sheath spaces may occur (especially bites overlying the metacarpal-phalangeal areas).
- Infection
- Rate of infection
- Dog bites: 3 " “18%
- Cat bites: 28 " “80%
- Human bites: 15 " “20%
- More recent studies have suggested an incidence of infection after dog and cat bites to be closer to 2 " “3%.
- 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
- Cat: Pasteurella multocida and Pasteurella septica
- Common anaerobes include Fusobacterium, bacterioids, Porphyromonas, and Prevotella.
- Infected human bites
- Streptococcus anginosus
- Staphylococcus aureus
- Eikenella corrodens
- Fusobacterium species
- Prevotella species
Diagnosis
History
- Animal bites
- Type of animal
- Apparent health of the animal
- Provocation for the attack
- Location of the bite or bites
- Availability of animal for undergoing observation (i.e., Is it a 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 & Interpretation
Lab
- Blood culture if fever or systemic toxicity is noted
- Aerobic and anaerobic cultures from infected wounds
Imaging
In penetrating injuries overlying bones or joints, consider radiography to evaluate for presence of fracture, foreign body (e.g., tooth), and air within joint. ‚
Diagnostic Procedures/Other
No tests routinely done ‚
Treatment
Medication
- Antibiotics: Data are often contradictory. In general:
- All cat bites should be treated with prophylactic antibiotics, due to high risk of infection with P. multocida.
- 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).
- All human bites should be treated with antibiotic prophylaxis. 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 plusclindamycin.
- Bites to the hand, face, deep puncture wounds, and wounds in immunocompromised patients may be treated empirically.
- Skin and soft tissue infections requiring hospitalization:
- Ampicillin/sulbactam IV 150 mg ampicillin/kg/24 h in 4 divided doses
- For penicillin-allergic patients, 3rd-generation cephalosporin
- Antibiotics with poor activity against Pasteurella include penicillinase-resistant penicillins, clindamycin, and aminoglycosides.
- 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; immune-compromised patients should receive a 5th 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.
Alert
A bite with a break in the skin is considered low risk, and a bite with intact skin is felt to pose no risk. ‚
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.
Issues for Referral
Local regulations dictate the reporting of animal bites to health departments. ‚
Ongoing Care
Follow-up Recommendations
Patient Monitoring
- Signs and symptoms of infection
- All patients with significant bites should receive follow-up 48 hours after bite.
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. ‚
Additional Reading
- Havens ‚ PL, American Academy of Pediatrics, Committee on Pediatric AIDS. Postexposure prophylaxis in children and adolescents for nonoccupational exposure to human immunodeficiency virus. Pediatrics. 2003;111(6):1475 " “1489. ‚ [View Abstract]
- Medeiros ‚ IM, Saconato ‚ H. Antibiotic prophylaxis for mammalian bites. Cochrane Database Syst Rev. 2008;(2):CD001738. ‚ [View Abstract]
- Rupprecht ‚ CE, Briggs ‚ D, Brown ‚ CM, et al. Use of a reduced (4-dose) vaccine schedule for postexposure prophylaxis to prevent human rabies: recommendations of the advisory committee on immunization practices. MMWR Recomm Rep. 2010;59(RR-2):1 " “9. ‚ [View Abstract]
- Talan ‚ DA, Abrahamian ‚ FM, Moran ‚ GJ, Emergency Medicine Human Bite Infection Study Group. Clinical presentation and bacteriologic analysis of infected human bites in patients presenting to the emergency departments. Clin Infect Dis. 2003;37(11):1481 " “1489. ‚ [View Abstract]
- Wu ‚ PS, Beres ‚ A, Tashjian ‚ DB, et al. Primary repair of facial dog bite injuries in children. Pediatr Emerg Care. 2011:27(9):801 " “813. ‚ [View Abstract]
Codes
ICD09
- 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
ICD10
- 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)
FAQ
- Q: What are the clinical features of Pasteurella infections?
- A: Infections caused by Pasteurella tend to progress rapidly, usually over a 12 " “24-hour period, and are characterized by tenderness and purulent drainage. The rapid progression of these infections tends to distinguish them from wounds that are infected with S. aureus and other pathogens.
- Q: Why are cat bites often more severe than dog bites?
- A: Cat bites are associated with puncture-type wounds and are more likely to involve Pasteurella infection, which is generally more aggressive than other organisms. However, dog bite infections may also be caused by Pasteurella.