AUTHOR AND EDITOR INFORMATION

Section 1 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

INTRODUCTION

Section 2 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Background

Human bite wounds have a notorious reputation, which is mostly based on one injury, the closed-fist injury. Human bites in other areas pose no greater risk than animal bites. Three general types of injuries can lead to complications: (1) closed-fist injury, (2) chomping injury to the finger, and (3) puncture-type wounds about the head caused by clashing with a tooth. Otherwise, the general principles of contaminated wound management apply to human bite wounds.

For more information, see Medscape's Wound Management Resource Center.

Pathophysiology

In a closed-fist injury, forces sufficient to break the skin from striking an opponent's tooth often inoculate the extensor tendon and its sheath. As the hand is flexed at the time of impact, the bacterial load is transferred caudally when the hand is opened and the tendon slides back to its relaxed state. Resulting contamination cannot be removed readily through normal cleansing and irrigation.

When a finger is bitten, such as in a chomping-type injury, tendons and their overlying sheaths are in close proximity to the skin. The wound may appear to be a minor abrasion-type injury, but careful inspection is required to rule out deep injury.

When a tooth strikes the head, even a deep puncture wound may appear innocuous. Deep, subgaleal, bacterial contamination is possible. This is especially true in young children who have relatively thin soft scalp and forehead tissue.

Frequency

United States

Exact incidence of human bite wounds is unknown, and many cases do not come to medical attention. Institutionalized patients with poor impulse control create a high-risk environment for human bite wounds. Lesch-Nyhan syndrome is an uncommon disorder that includes self-mutilation through biting.

Mortality/Morbidity

• The primary concern with human bites of the hand is infection, which can be severe because of spread along tendon sheaths and deep into the hand. Surgical incision and drainage may be needed. Resultant scarring and tissue damage may compromise normal function of the hand.
• Infection also is the major complication of bites in other areas of the body. Most can be treated adequately; however, infections of poorly vascularized structures, such as ear cartilage, may be difficult to treat.
• Other serious infectious complications such as osteomyelitis of the skull vault, necrotizing fasciitis, and septic arthritis have been associated with human bites. Transmission of human immunodeficiency virus (HIV) has been reported as a result of a human bite wound.

Sex

• Males generally are at higher risk than females for bite wounds due to their typically more aggressive nature. Closed-fist injuries are encountered almost exclusively in young males.

Age

• Closed-fist injuries occur most often in adolescents and adults younger than 40 years.
• Toddlers frequently bite one another, but injuries usually are superficial and low risk.
• Penetrating tooth injuries of the scalp and forehead pose a higher risk to young patients than to older patients.

CLINICAL

Section 3 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

History

• Consider all injuries dorsal to the metacarpophalangeal (MCP) joint bite wounds until proven otherwise. Explanations offered for such wounds often are misleading, thus extreme caution is necessary. While a careful explanation of the need for an accurate history may elicit the truth from the patient, experienced emergency physicians often treat such injuries as bites regardless of the history.
• Most bite wound infections are present at the initial ED visit. With closed-fist injuries, the initial injury often appears minor to the patient, thus no care is sought until infection develops. If a child receives a small laceration to the scalp or forehead during unwitnessed horseplay, carefully ascertain whether a tooth caused the wound to minimize complications.
• Other aspects of a patient's history that may influence care include tetanus immunization status, time delay from injury to presentation, disability encountered, and the presence of underlying immunosuppressive disease.

Physical

• Physicians must be wary of any laceration overlying the MCP joint. Additionally, carefully assess bite wounds of the fingers for deeper penetration into the tendon apparatus. Extending the wound may be necessary to fully evaluate the underlying structures and the extent of injury.
• The following points should be noted for specific bite wounds:
• • MCP wounds (closed-fist injury) - Integrity of the extensor tendons, signs of infection, crepitation, loss of knuckle height
  • Chomping injuries of the finger - Integrity of the extensor and flexor tendons, evidence of infection including flexor tenosynovitis
  • Ear bites - Loss of tissue, violation of cartilage
  • Other bites - Tissue loss, depth of penetration

Causes

• As with most intentional injuries, human bites often are the result of an incident involving alcohol.
• Domestic violence may be a factor.
• Child abuse may be associated with bite wounds from adults.

DIFFERENTIALS

Section 4 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

WORKUP

Section 5 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Lab Studies

• Routine laboratory studies: These are generally not indicated because the injured population is usually young and healthy. Diagnosis of infection is clinical.
• Wound culture: Microbiology of human bite wounds is fairly consistent, yet an untreated infected bite generally is cultured if purulence is present.

Imaging Studies

• Radiography
• • In closed-fist injuries, an underlying metacarpal head fracture is possible. This may dictate inpatient treatment.
  • Infected bites of the hand of some duration may have evidence of osteomyelitis on plain radiographs.
  • If history indicates that a tooth was broken during the incident, a radiograph may be indicated to examine for a foreign body.

Procedures

• Wound care

TREATMENT

Section 6 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Prehospital Care

• Recovery of avulsed tissue parts (eg, ear, finger) is an important consideration for prehospital providers. Otherwise, human bite wound management generally is uncomplicated and involves temporary dressing and transport.
• Avulsed parts should be wrapped in sterile gauze dressing that is soaked with normal saline and placed in a plastic bag that is, in turn, placed in a container of ice water.

Emergency Department Care

The acute, non-infected human bite

• Cleanse and debride as usual
• Tetanus prophylaxis as indicated
• Antibiotic prophylaxis
• • The literature regarding prophylaxis of human bite wounds is sparse. Only 2 randomized controlled trials directly address the question. In the first, patients with acute, non-infected human bites to the hand were randomized to prophylaxis with placebo, an oral cephalosporin, or a parenteral cephalosporin plus penicillin. Bites involving joints or tendons were excluded from this study.  The results were dramatic, with 47% of the placebo group developing infection, while none of the subjects treated with antibiotics developed infection.¹
  • A larger, more recent trial attempted to address the question in patients with “low-risk” human bites by randomizing them to placebo or an oral cephalosporin plus penicillin. This trial excluded patients with bites to the hands, feet, or cartilaginous structures, and no patient in this trial had a bite wound that penetrated deep to the epidermis. The rate of infection in this study was much lower, with only one patient in the placebo group becoming infected. There was no statistically significant difference compared to the group treated with antibiotics.²
  • A large, retrospective series examining human bite wounds in children found that none of the bites manifesting as abrasions became infected, while the rate of infection was much higher in bite wounds that caused punctures or lacerations.³
  • From these data, one can conclude that it is probably efficacious to treat acute, non-infected human bite wounds with antibiotics if the wound involves the hands, feet, cartilaginous structures, or is deeper than the epidermal layer.
• Special cases
• • Closed-fist injuries: An underlying fracture dictates inpatient treatment under certain circumstances. After appropriate anesthesia, explore the wound for joint space violation or tendon injury. Involvement of the joint space indicates admission. Consider patients with tendon injuries, which usually are present, for admission. Proper wound assessment includes using a tourniquet and extending the wound as needed to improve visualization. Provide outpatient treatment of these wounds (careful wound cleansing, antibiotic coverage, bulky dressing or splint, elevation) only in consultation with hand or orthopedic service. Early, mandatory follow-up care is essential.
  • Chomping injuries: Treat non-infected wounds that appear to violate the tendon apparatus in the same manner as non-infected closed-fist injuries.
  • Puncture wounds: These most commonly are encountered about the head. Such wounds are difficult to clean adequately unless extended to allow for effective irrigation. Even in the absence of infection, such wounds are best left open and closed secondarily, if cosmetically necessary.
  • Bites to the ear or nose: When associated with tissue loss, these wounds require consultation with plastic surgery or ear, nose, and throat (ENT) service. Seeking consult for a bite that violates cartilage in these areas also is prudent because of poor blood supply to cartilage and difficulties in treating chondritis.

The infected human bite wound

• The current recommendations from the Infectious Disease Society of America (IDSA) call for the use of amoxicillin/clavulanate or ampicillin/sulbactam. TMP/SMX plus clindamycin is an acceptable alternative in the penicillin-allergic patient.⁴
• Infected closed-fist injuries are a special case because of the deep nature of these infections and relatively poor vascular supply to the tendons and other connective tissue. Admitting patients for intravenous (IV) antibiotic therapy is generally considered appropriate is these cases. Surgical debridement and drainage also may be necessary.

Other considerations

• HIV transmission has been noted only rarely after a human bite. Exposure to saliva alone is not considered a risk factor for HIV (or hepatitis) transmission. Transmission requires HIV-infected blood mixed in the saliva of the biter and a skin break on the victim. The reverse consideration also is important in that blood drawn from an HIV-infected victim would come in contact with the mucous membranes of the biter. A 2005 Centers for Disease Control and Prevention recommendation states that postexposure prophylaxis with a 28-day course of highly active antiretroviral therapy (HAART) should be used in either of these 2 scenarios.⁵

Consultations

• In general, consult hand and/or orthopedic service for infected human bites of the hand and those involving a fracture, joint space violation, or significant tendon injury. Consider consultation or agreed-upon protocols for other human bites to the hand.
• Consult plastic surgery or ENT service for significant injuries to the special structures about the face and for wounds involving significant tissue loss.

MEDICATION

Section 7 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

The only drug therapy of significance in human bites is antibiotic treatment. Bacterial flora include that of the mouth and skin. Theoretically, penicillin treats oral pathogens and may suffice for prophylactic treatment as Staphylococcus species probably only infect bite wounds secondarily.

Once a human bite is infected, beta-lactamase–producing staphylococci must be addressed. Eikenella corrodens may not be covered by first-generation cephalosporins. Additionally, Eikenella species are resistant to clindamycin, penicillinase-resistant semisynthetic penicillins, and metronidazole. A broad-spectrum antibiotic, rather than combination therapy, is the usual choice for infected bite wounds. An in vitro study of 50 infected human bites by Talan et al indicated that amoxicillin-clavulanic acid and moxifloxacin demonstrated excellent activity against common isolates.⁶

Drug Category: Antibiotics

Therapy must cover all likely pathogens in the context of the clinical setting.

Drug Category: Immunizing agents

These agents are used to immunize patients against tetanus.

FOLLOW-UP

Section 8 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Further Outpatient Care

• Patients with human bite wounds (other than those with superficial wounds discharged from the ED) should have early, mandatory follow-up care within 1-2 days.

Complications

• Infection and resulting sequelae are the main complications in human bites. These include serious soft tissue infection, tendon damage, tissue contracture, and osteomyelitis.
• Cosmetic deformity may be a complication.

Prognosis

• The prognosis is generally excellent, except for possible sequelae from serious infection.

Patient Education

• For excellent patient education resources, visit eMedicine's Bites and Stings Center. Also, see eMedicine's patient education article Human Bites.

MISCELLANEOUS

Section 9 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Medical/Legal Pitfalls

• Failure to elicit a careful history regarding the circumstances of a wound
• Failure to treat a human bite as a complicated laceration
• • If either of these lead to a poor outcome, the physician can be faulted for taking an improper history. Key points are to be extremely cautious with wounds over the MCP joints, with hand wounds in general, and with small lacerations about the head and forehead in young children.
  • Documentation of the mechanism reported is essential to avoid later questions regarding treatment.
• Failure to report suspected child abuse (reporting is mandatory for health care professionals in most jurisdictions)

REFERENCES

Section 10 of 10

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

1. Zubowicz VN, Gravier M. Management of early human bites of the hand: a prospective randomized study. Plast Reconstr Surg. Jul 1991;88(1):111-4. [Medline].
2. Broder J, Jerrard D, Olshaker J, Witting M. Low risk of infection in selected human bites treated without antibiotics. Am J Emerg Med. Jan 2004;22(1):10-3. [Medline].
3. Baker MD, Moore SE. Human bites in children. A six-year experience. Am J Dis Child. Dec 1987;141(12):1285-90. [Medline].
4. Stevens DL, Bisno AL, Chambers HF, Everett ED, Dellinger P, Goldstein EJ. Practice guidelines for the diagnosis and management of skin and soft-tissue infections. Clin Infect Dis. Nov 15 2005;41(10):1373-406. [Medline].
5. Pretty IA, Anderson GS, Sweet DJ. Human bites and the risk of human immunodeficiency virus transmission. Am J Forensic Med Pathol. Sep 1999;20(3):232-9. [Medline].
6. Talan DA, Abrahamian FM, Moran GJ, et al. Clinical presentation and bacteriologic analysis of infected human bites in patients presenting to emergency departments. Clin Infect Dis. Dec 1 2003;37(11):1481-9. [Medline].
7. Bunzli WF, Wright DH, Hoang AT, et al. Current management of human bites. Pharmacotherapy. Mar-Apr 1998;18(2):227-34. [Medline].
8. Chen E, Hornig S, Shepherd SM, Hollander JE. Primary closure of mammalian bites. Acad Emerg Med. Feb 2000;7(2):157-61. [Medline].
9. Donkor P, Bankas DO. A study of primary closure of human bite injuries to the face. J Oral Maxillofac Surg. May 1997;55(5):479-81; discussion 481-2. [Medline].
10. Gilbert DN, Moellering RC, Sande MA. Human bites. In: The Sanford Guide to Antimicrobial Therapy. 30^th ed. Antimicrobial Therapy Inc; 2000:37.
11. Kelly IP, Cunney RJ, Smyth EG, Colville J. The management of human bite injuries of the hand. Injury. Sep 1996;27(7):481-4. [Medline].
12. Lindsey D, Christopher M, Hollenbach J, et al. Natural course of the human bite wound: incidence of infection and complications in 434 bites and 803 lacerations in the same group of patients. J Trauma. Jan 1987;27(1):45-8. [Medline].
13. Miura I, Ohshima A, Takahashi N, et al. A new non-random chromosomal translocation t(3;6)(q27;p21.3) associated with BCL6 rearrangement in two patients with non-Hodgkin's lymphoma. Int J Hematol. Oct 1996;64(3-4):249-56. [Medline].
14. Schweich P, Fleisher G. Human bites in children. Pediatr Emerg Care. Jun 1985;1(2):51-3. [Medline].
15. Smith DK, Grohskopf LA, Black RJ, et al. Antiretroviral postexposure prophylaxis after sexual, injection-drug use, or other nonoccupational exposure to HIV in the United States: recommendations from the U.S. Department of Health and Human Services. MMWR Recomm Rep. Jan 21 2005;54(RR-2):1-20. [Medline].
16. Smith PF, Meadowcroft AM, May DB. Treating mammalian bite wounds. J Clin Pharm Ther. Apr 2000;25(2):85-99. [Medline].

Article Last Updated: Jul 23, 2008