(See also Spirochetes: Rat-Bite Fever.)
Human and other mammal (mostly dog and cat, 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; about 10 to 20 people, mostly children, die from dog bites each year. However, most bites cause relatively minor wounds.
In addition to tissue trauma, infection from 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 (see Brain Infections: Rabies). Monkey bites, usually restricted in the US to animal laboratory workers, 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 (see also Hand Disorders: Infected Bite Wounds of the Hand) carry a higher risk of infection than bites to other sites. Specific infections include cellulitis, tenosynovitis, septic arthritis, and osteomyelitis. This higher risk is a particular concern after a clenched-fist strike to the mouth (a fight bite), the most common human bite wound. 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 proved 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.
Human bites sustained in an altercation are often attributed to other or vague causes to avoid involvement of the authorities or to ensure insurance coverage. Domestic violence is often denied.
Wounds are evaluated for damage to underlying structures (eg, nerves, vasculature, tendons, bone) and for foreign bodies (see Lacerations: Evaluation). 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 are explored under sterile conditions to assess tendon, bone, and joint involvement and to detect retained foreign bodies. Wounds inflicted by chomping may appear to be minor abrasions but should be examined to rule out deep injury.
Culturing fresh wounds is not valuable for targeting antimicrobial therapy, but infected wounds should be cultured. For patients with human bites, screening for hepatitis or HIV is recommended only if the attacker is known or suspected to be seropositive.
Hospitalization is indicated if complications mandate very close monitoring, particularly when patient characteristics predict a high risk of nonadherence with outpatient follow-up. Hospitalization should be considered in the following circumstances:
Priorities of treatment include wound cleaning, debridement, closure, and infection prophylaxis.
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, that have minimal damage and can be cleansed effectively). Many wounds should initially be left open, including the following:
In addition, in immunocompromised patients, wound healing may be better with delayed closure. Other wounds (ie, fresh, cutaneous lacerations) can usually be closed after appropriate wound hygiene. 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 continuously elevated (eg, hanging from a pole).
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.
Thorough wound cleansing 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. Drugs do not prevent infection in heavily contaminated or inadequately cleaned wounds. However, many practitioners prescribe prophylactic antibiotics for bites to the hand and some other bites (eg, cat bites, monkey bites).
Infections are treated with antimicrobials initially chosen based on animal species (see Table 1: Bites and Stings: Antimicrobials for 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 (see Hepatitis: Prevention) and HIV (see Human Immunodeficiency Virus (HIV): Postexposure prophylaxis (PEP)) as indicated by patient and attacker serostatus. If status is unknown, prophylaxis is not indicated.
Last full review/revision February 2013 by Robert A. Barish, MD, MBA; Thomas Arnold, MD
Content last modified March 2013