eMedicine Specialties > Emergency Medicine > Environmental

Bites, Human

Jeffrey Barrett, MD, Assistant Professor, Department of Emergency Medicine, Temple University School of Medicine
Robert M McNamara, MD, FAAEM, Chair and Professor, Department of Emergency Medicine, Temple University School of Medicine

Updated: Apr 23, 2009

Introduction

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.

International

In a 4-year retrospective review in the United Kingdom, 421 (13%) human bites were identified out of 3136 case notes. The majority of those bitten were young males, with 44% of the males aged 16-25 years. The male-to-female ratio was 3:1.¹

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

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.

Differential Diagnoses

Bites, Animal
Bites, Insects
Hand Infections

Workup

Laboratory 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

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.²
- 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.³
- 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.⁴
- 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. In other words, prophylax all human bite wounds except for those manifesting as superficial abrasions in locations other than the hands, ears, and nose.
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.⁵
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.⁶

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

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.⁷

Antibiotics

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

Amoxicillin/clavulanate (Augmentin)

Drug combination that extends antibiotic spectrum of this penicillin to include bacteria normally resistant to beta-lactam antibiotics. DOC for noninfected human bite wounds. Dosing is based on amoxicillin component. Indicated for skin and skin structure infections caused by beta-lactamase-producing strains of Staphylococcus aureus.

Dosing

Adult

875 mg PO bid for 5 d

Pediatric

45 mg/kg/d PO divided q12h

Interactions

Risk of bleeding increases when coadministered with warfarin or heparin, possibly because of additive effects

Contraindications

Documented hypersensitivity

Precautions

Pregnancy

B - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals

Precautions

Use may precipitate pseudomembranous colitis;
give for minimum of 10 d to eliminate organism and prevent sequelae (endocarditis, rheumatic fever); following treatment, perform cultures to confirm eradication of streptococci

Ampicillin/sulbactam sodium (Unasyn)

Drug combination that uses beta-lactamase inhibitor with ampicillin; covers skin, enteric flora, and anaerobes. DOC for infected bites.

Dosing

Adult

1.5 (1 g ampicillin + 0.5 g sulbactam) to 3 g (2 g ampicillin + 1 g sulbactam) IV q6h; not to exceed 4 g/d sulbactam or 8 g/d ampicillin

Pediatric

<12 years: Not established

Interactions

Probenecid and disulfiram elevate ampicillin levels; allopurinol decreases ampicillin effects and has additive effects on ampicillin rash; may decrease effects of oral contraceptives

Contraindications

Documented hypersensitivity

Precautions

Pregnancy

B - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals

Precautions

Adjust dose in renal failure; evaluate rash and differentiate from hypersensitivity reaction

Cefoxitin (Mefoxin)

Alternative drug for infected bites; second-generation cephalosporin indicated for management of infections caused by susceptible gram-positive cocci and gram-negative rods. Many infections that are caused by gram-negative bacteria and are resistant to some cephalosporins and penicillins respond to cefoxitin.

Dosing

Adult

2 g IV q8h

Pediatric

>3 months: 80-160 mg/kg/d IV divided q4-6h

Interactions

Probenecid may increase effects; coadministration with aminoglycosides or furosemide may increase nephrotoxicity (closely monitor renal function)

Contraindications

Documented hypersensitivity

Precautions

Pregnancy

B - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals

Precautions

Bacterial or fungal overgrowth of nonsusceptible organisms may occur with prolonged use or repeated treatment; caution in patients with previously diagnosed colitis

Moxifloxacin (Avelox)

Inhibits the A subunits of DNA gyrase, resulting in inhibition of bacterial DNA replication and transcription.

Dosing

Adult

400 mg PO/IV qd

Pediatric

<18 years: Not recommended
>18 years: Administer as in adults

Interactions

Antacids and electrolyte supplements reduce absorption; loop diuretics, probenecid, and cimetidine increase serum levels; NSAIDs enhance CNS stimulating effect; may increase toxicity of theophylline, caffeine, cyclosporine, and digoxin (monitor digoxin levels); may increase effects of anticoagulants (monitor PT); ferrous sulfate decreases bioavailability (administer moxifloxacin 4 h prior or 8 h following ferrous sulfate); coadministration with drugs that prolong QTc interval (quinidine, procainamide, amiodarone, sotalol, erythromycin, tricyclic antidepressants) increase risk of life-threatening arrhythmia

Contraindications

Documented hypersensitivity; known Q-T prolongation; concurrent administration of drugs that cause Q-T prolongation

Precautions

Pregnancy

C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus

Precautions

In prolonged therapy, perform periodic evaluations of organ system functions (eg, renal, hepatic, hematopoietic); superinfections may occur with prolonged or repeated antibiotic therapy; fluoroquinolones have induced seizures in CNS disorders and caused tendinitis or tendon rupture

Immunizing agents

These agents are used to immunize patients against tetanus.

Tetanus immune globulin (Hyper-Tet)

Used for passive immunization of any person with a wound that may be contaminated with tetanus spores.

Dosing

Adult

Prophylaxis: 250-500 U IM in opposite extremity to tetanus toxoid lesion
Clinical tetanus: 3000-10,000 U IM

Pediatric

Prophylaxis: 250 U IM in opposite extremity to tetanus toxoid
Clinical tetanus: 3000-10,000 U IM

Interactions

None reported

Contraindications

Since antibodies in globulin preparation may interfere with immune response to vaccination, do not administer within 3 mo of live-virus immune globulin administration; may be necessary to revaccinate persons who received immune globulin shortly after live-virus vaccination

Precautions

Pregnancy

C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus

Precautions

Persons with isolated IgA deficiency have potential for developing antibodies to IgA and may have anaphylactic reactions to subsequent administration of blood products that contain IgA; do not perform skin testing since intradermal injection of concentrated gamma globulin may cause localized area of inflammation and can be misinterpreted, causing medication to be withheld from a patient not allergic to this material; true allergic responses to human gamma globulin given in prescribed IM manner are extremely rare; do not admix with other medications since usually incompatible

Follow-up

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

Medicolegal 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

Harrison M. A 4-year review of human bite injuries presenting to emergency medicine and proposed evidence-based guidelines. Injury. Jan 31 2009;[Medline].
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].
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].
Baker MD, Moore SE. Human bites in children. A six-year experience. Am J Dis Child. Dec 1987;141(12):1285-90. [Medline].
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].
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].
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].
Bunzli WF, Wright DH, Hoang AT, et al. Current management of human bites. Pharmacotherapy. Mar-Apr 1998;18(2):227-34. [Medline].
Chen E, Hornig S, Shepherd SM, Hollander JE. Primary closure of mammalian bites. Acad Emerg Med. Feb 2000;7(2):157-61. [Medline].
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].
Gilbert DN, Moellering RC, Sande MA. Human bites. In: The Sanford Guide to Antimicrobial Therapy. 30^th ed. Antimicrobial Therapy Inc; 2000:37.
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].
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].
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].
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].
Schweich P, Fleisher G. Human bites in children. Pediatr Emerg Care. Jun 1985;1(2):51-3. [Medline].
Smith PF, Meadowcroft AM, May DB. Treating mammalian bite wounds. J Clin Pharm Ther. Apr 2000;25(2):85-99. [Medline].
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Keywords

human bites, human bite wound, closed-fist injury, chomping injury, puncture-type wound, infected human bite wounds, bite wounds, bite injury

Contributor Information and Disclosures

Author

Jeffrey Barrett, MD, Assistant Professor, Department of Emergency Medicine, Temple University School of Medicine
Jeffrey Barrett, MD is a member of the following medical societies: American Academy of Emergency Medicine and Society for Academic Emergency Medicine
Disclosure: Nothing to disclose.

Coauthor(s)

Robert M McNamara, MD, FAAEM, Chair and Professor, Department of Emergency Medicine, Temple University School of Medicine
Robert M McNamara, MD, FAAEM is a member of the following medical societies: American Academy of Emergency Medicine, American Medical Association, Pennsylvania Medical Society, and Society for Academic Emergency Medicine
Disclosure: Nothing to disclose.

Medical Editor

Samuel M Keim, MD, Associate Professor, Department of Emergency Medicine, University of Arizona College of Medicine
Samuel M Keim, MD is a member of the following medical societies: American Academy of Emergency Medicine, American College of Emergency Physicians, American Medical Association, American Public Health Association, and Society for Academic Emergency Medicine
Disclosure: Nothing to disclose.

Pharmacy Editor

Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine
Disclosure: eMedicine Salary Employment

Managing Editor

James Steven Walker, DO, MS, Clinical Professor of Surgery, Department of Surgery, University of Oklahoma Health Sciences Center
James Steven Walker, DO, MS is a member of the following medical societies: American Academy of Emergency Medicine, American College of Emergency Physicians, American College of Osteopathic Emergency Physicians, and American Osteopathic Association
Disclosure: Nothing to disclose.

CME Editor

John D Halamka, MD, MS, Associate Professor of Medicine, Harvard Medical School, Beth Israel Deaconess Medical Center; Chief Information Officer, CareGroup Healthcare System and Harvard Medical School; Attending Physician, Division of Emergency Medicine, Beth Israel Deaconess Medical Center
John D Halamka, MD, MS is a member of the following medical societies: American College of Emergency Physicians, American Medical Informatics Association, Phi Beta Kappa, and Society for Academic Emergency Medicine
Disclosure: Nothing to disclose.

Chief Editor

Jonathan Adler, MD, Attending Physician, Department of Emergency Medicine, Massachusetts General Hospital; Division of Emergency Medicine, Harvard Medical School
Jonathan Adler, MD is a member of the following medical societies: American Academy of Emergency Medicine and Society for Academic Emergency Medicine
Disclosure: Nothing to disclose.

Further Reading

Clinical guidelines

Management of human bite wounds. University of Texas, School of Nursing, Family Nurse Practitioner Program. Management of human bite wounds. Austin (TX): University of Texas, School of Nursing; 2007 May. 22 p.

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. Smith DK, Grohskopf LA, Black RJ, Auerbach JD, Veronese F, Struble KA, Cheever L, Johnson M, Paxton LA, Onorato IM, Greenberg AE. 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 2005 Jan 21;54(RR-2):1-26. [126 references] PubMed

Practice guidelines for the diagnosis and management of skin and soft-tissue infections. Stevens DL, Bisno AL, Chambers HF, Everett ED, Dellinger P, Goldstein EJ, Gorbach SL, Hirschmann JV, Kaplan EL, Montoya JG, Wade JC. Practice guidelines for the diagnosis and management of skin and soft-tissue infections. Clin Infect Dis 2005 Nov 15;41(10):1373-406. [236 references] PubMed