Human and other mammal bites (mostly dog and cat bites, but also squirrel, gerbil, rabbit, guinea pig, and monkey bites) are common and occasionally cause significant morbidity and disability. The hands, extremities, and face are most frequently affected, although human bites can occasionally involve breasts and genitals.
Bites by large animals sometimes cause significant tissue trauma; approximately 30 to 80 people in the United States, mostly children, die from dog bites each year. However, most bites cause relatively minor wounds (1).
(See also Rat-Bite Fever.)
Infection
In addition to tissue trauma, infection due to the biting organism’s oral flora is a major concern. Human bites can theoretically transmit viral hepatitis and HIV. However, HIV transmission is unlikely because the concentration of HIV in saliva is much lower than in blood and salivary inhibitors render the virus ineffective.
Rabies is a risk with certain mammal bites (eg, dogs, bats). Monkey bites carry a small risk of herpes simian B virus (Herpesvirus simiae) infection, which causes vesicular skin lesions at the inoculation site and can progress to encephalitis, which is often fatal.
Bites to the hand by another human carry a higher risk of infection than bites to other sites. Specific hand infections caused by bites include
A fight bite is the most common human bite wound. It results from a clenched-fist strike to the mouth of another person and is a particular risk for infection. In fight bites, the skin wound moves away from the underlying damaged structures when the hand is opened, trapping bacteria inside. Patients often delay seeking treatment, allowing bacteria to multiply.
Human bites to sites other than the hand have not been shown to carry a greater risk of infection than bites from other mammals.
Cat bites to the hand also have a high risk of infection because cats’ long, slender teeth often penetrate deep structures, such as joints and tendons, and the small punctures are then sealed off.
Reference
1. U.S. Centers for Disease Control and Prevention (CDC). QuickStats: Number of Deaths Resulting from Being Bitten or Struck by a Dog, by Sex — National Vital Statistics System, United States, 2011–2021. MMWR Morb Mortal Wkly Rep. 2023;72:999. DOI: http://dx.doi.org/10.15585/mmwr.mm7236a6
Diagnosis of Human and Mammal Bites
Examination of the bite and surrounding tissue
Sometimes imaging to assess for damage to underlying nerve, tendon, bone, and vasculature and for presence of foreign bodies
Tests for local or systemic infection
Human bites sustained in an altercation are often attributed to other causes (eg, abrasions or lacerations from striking an object or falling to the ground) to avoid involvement of the authorities. People who have experienced domestic violence are often reluctant to disclose the source of an injury.
Pearls & Pitfalls
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Wounds are evaluated for damage to underlying structures (eg, nerves, vasculature, tendons, bone) and for foreign bodies. Evaluation should focus on careful assessment of function and the extent of the bite. Wounds over or near joints should be examined while the injured area is held in the same position as when the bite was inflicted (eg, with fist clenched). Wounds inflicted by repeated low bites may appear to be minor abrasions but should be examined to exclude deep injury.
Wounds are explored under sterile conditions to assess tendon, bone, and joint involvement and to detect retained foreign bodies. If a retained foreign body is a possibility, imaging (eg, radiograph for radiopaque foreign bodies, such as most teeth) may be done. Ultrasound is a valuable tool for detecting subcutaneous foreign bodies.
Culturing fresh wounds is not valuable for targeting antimicrobial therapy; however, if a wound is infected, sending a sample for culture should be considered. For patients with human bites, screening for hepatitis or HIV is recommended only if the attacker is known or suspected to be seropositive.
Treatment of Human and Mammal Bites
Meticulous wound care
Selective wound closure
Selective use of prophylactic antibiotics
Priorities of treatment include wound cleaning, debridement, closure, and infection prophylaxis, including for tetanus (see table Tetanus Prophylaxis in Routine Wound Management).
Hospitalization is indicated if complications from a bite mandate close monitoring, particularly when patient characteristics predict a high risk of nonadherence with outpatient follow-up. Hospitalization should be considered in the following circumstances:
Infected human bite (including clenched-fist injuries)
Moderately or severely infected non-human bite
Loss of function is evident
Wound threatens or has damaged deep structures
Wound is disabling or difficult to care for at home (eg, significant wounds to both hands or both feet, hand wounds that require continuous elevation)
Wound care
Bite wounds should first be cleaned with a mild antibacterial soap and water (tap water is sufficient), then pressure irrigated with copious volumes of saline solution using a syringe and IV catheter. A local anesthetic should be used as needed. Dead and devitalized tissue should be debrided, taking particular care in wounds involving the face or the hand.
Wound closure is done only for select wounds (ie, fresh, cutaneous wounds that have minimal damage and can be cleaned effectively). Many wounds should initially be left open, including those with the following characteristics:
Human bite wounds
Puncture wounds
Wounds to the hands, feet, perineum, or genitals
Involve deeper structures (eg, tendon, cartilage, bone)
Severe edema
Signs of inflammation (eg, erythema, surrounding skin is warm)
Occurred more than several hours prior to treatment
Occurred in a contaminated environment (eg, marine, field, sewers) or any wound that is heavily contaminated
In addition, in immunocompromised patients, wound healing may be better with delayed primary closure. Results with delayed primary closure are comparable to those with primary closure, so little is lost by leaving the wound open initially if there is any question.
Hand bites should be wrapped in sterile gauze, splinted in position of function (slight wrist extension, metacarpophalangeal and both interphalangeal joints in flexion). If wounds are moderate or severe, the hand should be elevated as much as possible (eg, using a sling).
Facial bites may require reconstructive surgery given the cosmetic sensitivity of the area and the potential for scarring. Primary closure of dog bites of the face in children has shown good results, but consultation with a plastic surgeon may be indicated.
Infected wounds may require debridement, suture removal, soaking, splinting, elevation, and IV antibiotics, depending on the specific infection and clinical scenario. Joint infections and osteomyelitis require prolonged IV antibiotic therapy and orthopedic consultation.
Antimicrobials
Thorough wound cleaning is the most effective and essential way to prevent infection and often suffices. There is no consensus on indications for prophylactic antibiotics. Studies have not confirmed a definite benefit, and widespread use of prophylactic antibiotics has the potential to select resistant organisms. Antibiotics do not prevent infection in heavily contaminated or inadequately cleaned wounds. However, many clinicians prescribe prophylactic antibiotics for bites to the hand and some other bites (eg, cat bites, monkey bites) (1).
Infections are treated with antimicrobials initially chosen based on animal species (see table Antimicrobials for Infected Bite Wounds). Culture results, when available, guide subsequent therapy.
Patients with human bites that cause bleeding or exposure to the biter's blood should receive postexposure prophylaxis for viral hepatitis and HIV as indicated by patient and attacker serostatus. If status is unknown, prophylaxis is not indicated.
Antimicrobials for Bite Wounds
Medication | Comments |
|---|---|
Human and dog bites | |
Amoxicillin/clavulanic acid | For outpatients Prophylaxis: Give for 3 days Treatment: Give for 5–7 days |
Ampicillin/sulbactam | For inpatients Effective against alpha-hemolytic streptococci, Staphylococcus aureus, and Eikenella corrodens |
Trimethoprim/sulfamethoxazole plus | For penicillin-allergic patients (use weight-appropriate doses for children) |
Clindamycin | |
Doxycycline | Alternative for dog bites in penicillin-allergic patients, except children < 8 years and pregnant women |
Clindamycin plus | Alternative for dog bites in adults |
A fluoroquinolone (eg, ciprofloxacin) | |
Cat bites* | |
Amoxicillin/clavulanic acid | For outpatients Prophylaxis: Give for 3 days Treatment: Give for 5–7 days |
A fluoroquinolone (eg, ciprofloxacin) | For prophylaxis and treatment in adults |
Clarithromycin | Alternative for children Effective against Pasturella multocida† |
Clindamycin | Alternative for children |
Monkey bites‡ | |
Acyclovir | For prophylaxis |
* Squirrel, gerbil, rabbit, and guinea pig bites rarely become infected, but when they do, they can be treated with the same medications used to treat infected cat bites. | |
† Bartonella henselae—see Cat-Scratch Disease—is also transmitted by cat bites. | |
‡ For treatment of infected monkey bites, use antibacterial medications similar to those used for infected human and dog bites. | |
Key Points
Infectious risk is high for hand wounds, particularly clenched-fist injuries.
Evaluate hand wounds with the hand in the position it was when the wound was inflicted.
Evaluate wounds for damage to nerve, tendon, bone, and vasculature and for the presence of foreign bodies.
Close only wounds that have minimal damage and can be cleaned effectively.
Decrease risk of infection by thorough mechanical cleaning, debridement, and sometimes antimicrobial prophylaxis.
Treatment reference
1. Stevens DL, Bisno AL, Chambers HF, et al. Practice guidelines for the diagnosis and management of skin and soft tissue infections: 2014 update by the Infectious Diseases Society of America [published correction appears in Clin Infect Dis. 2015 May 1;60(9):1448. doi: 10.1093/cid/civ114. Dosage error in article text]. Clin Infect Dis. 2014;59(2):e10-e52. doi:10.1093/cid/ciu444
