Initial management of animal and human bites

INTRODUCTION — Animal and human bites are a common problem. Proper care requires wound inspection for injury to deeper structures; meticulous wound care at the initial encounter; and decisions regarding primary closure, the provision of prophylactic antibiotics for wounds at high risk for infection, and prophylaxis for tetanus and rabies as indicated. EPIDEMIOLOGY — Animal bites are common. In the United States, there is an annual incidence of two to five million occurrences which account for about 1 percent of all visits to emergency departments. Approximately 10 percent of bite wounds presenting for medical attention require suturing and follow-up care, and 1 to 2 percent result in hospitalization. MICROBIOLOGY — The predominant pathogens in animal bite wounds are the oral flora of the biting animal and human skin flora. Infection usually results from a mixture of organisms. Common pathogens (in order of prevalence) include Pasteurella species, staphylococci, streptococci, and anaerobic bacteria. Capnocytophaga canimorsus, a fastidious gram-negative rod, can cause bacteremia and fatal sepsis after animal bites, especially in asplenic patients, chronic alcohol abusers, or those with underlying hepatic disease. Cat bites can also transmit Bartonella henselae, the organism responsible for cat scratch disease. Cat bites — Two-thirds of cat bites involve the upper extremities; scratches typically occur on the upper extremities or face. Deep puncture wounds are of particular concern because cats have long, slender, sharp teeth. When the hand is the target of such a puncture wound, bacteria can be inoculated below the periosteum or into a joint and result in osteomyelitis or septic arthritis INITIAL MANAGEMENT: Stabilization — Direct pressure should be applied to actively bleeding wounds and a neurovascular assessment should be performed in areas distal to the wound. Deep wounds to vital structures should be treated as major penetrating trauma. Wound preparation — Appropriate local anesthesia facilitates adequate wound cleansing. To reduce the counts of bacteria present in the wound, the surface should be cleaned with 1 percent povidone iodine or 1 percent benzalkonium chloride, and the depths irrigated with copious amounts of saline using pressure irrigation. Debridement of devitalized tissue is important to remove any nidus for infection. Primary closure — A clinician with prior training and experience in laceration repair may perform primary wound closure of simple lacerations due to dog bites. In contrast, most cat or human bites are left open to heal by secondary intention. In addition to these indications for primary wound closure of open lacerations, we suggest that the laceration meets ALL of the following criteria: ■Clinically uninfected ■Less than 12 hours old (24 hours on the face) ■NOT located on the hand or foot In particular, wounds to the face are usually closed promptly because good cosmesis is especially important, and infection of these wounds is uncommon Wounds at high risk for the development of infection should NOT be closed primarily in most cases [3,5,8,29,30]. These include: ■Crush injuries ■Puncture wounds ■Bites involving the hands and feet ■Wounds more than 12 hours old (24 hours old on face) ■Cat or human bites, except those to the face ■Bite wounds in compromised hosts (eg, immunocompromised, absent spleen or splenic dysfunction, venous stasis, diabetes mellitus [adults]) Surgical consultation — Surgical consultation is usually necessary for the following wounds [30]: ■Deep wounds that penetrate bone, tendons, joints, or other major structures ■Complex facial lacerations ■Wounds associated with neurovascular compromise ■Wounds with complex infections (eg, abscess formation, osteomyelitis, or joint infection) Antibiotic prophylaxis — Prophylactic antibiotics reduce the rate of infection due to some animal bites, especially cat bites. Although routine antibiotic prophylaxis is not recommended, prophylaxis is warranted in certain high-risk wounds . ■Deep puncture wounds (especially due to cat bites) ■Moderate to severe wounds with associated crush injury ■Wounds in areas of underlying venous and/or lymphatic compromise ■Wounds on the hand(s), genitalia, face, or in close proximity to a bone or joint (particularly the hand and prosthetic joints) ■Wounds requiring closure ■Bite wounds in compromised hosts (eg, immunocompromised, absent spleen or splenic dysfunction, and adults with diabetes mellitus) Tetanus and rabies prophylaxis — Viral prophylaxis after human bites — Any unvaccinated patient or individual negative for anti-HBs antibodies who is bitten by an individual positive for HBsAg should receive both hepatitis B immune globulin (HBIG) and hepatitis B vaccine Infected bites — To successfully manage an infected wound, the clinician must recognize early signs of infection and be aware of the likely pathogens. (See 'Infected wound' above.) If a bite wound appears to be infected, the following actions should be taken: ■Remove suture material, if previously repaired. ■Obtain Gram stain and aerobic and anaerobic cultures from the depth of an infected puncture or laceration prior to the initiation of antibiotics. The laboratory requisition should note that an animal or human bite wound is the culture source. ■Draw aerobic and anaerobic blood cultures prior to antibiotic therapy in patients with signs of systemic infection. ■Consult a surgeon for possible operative exploration, debridement, and drainage if abscess formation or suspected infection of bone, joint, or other major underlying structure (eg, clenched fist infections and other hand infections) is present. Debrided material should be sent for aerobic and anaerobic culture. ■Hospitalize patients with systemic symptoms or progression or development of infection despite receiving oral antibiotics. Empiric antibiotic therapy — Once a bite becomes infected, it is crucial to perform aggressive debridement and abscess drainage, as indicated, and to administer intravenous broad-spectrum antibiotics to cover probable infecting bacteria in patients with dog or cat bites (table 1) or human bites (table 2). A common approach involves initial IV therapy until infection is resolving followed by oral therapy to complete a course of 10 to 14 days. Empiric intravenous antibiotic therapy for animal bites Adults Children Options for empiric gram-negative and anaerobic coverage include: Monotherapy with a beta-lactam/beta-lactamase inhibitor, such as one of the following: Ampicillin-sulbactam (unasyn) 3 g every six hours 50 mg/kg per dose (based on ampicillin component) every six hours* Piperacillin-tazobactam (zosyn)4.5 g every eight hours 125 mg/kg per dose (based on piperacillin component) every eight hours* Ticarcillin-clavulanate (timentin)3.1 g every four hours 50 mg/kg per dose (based on ticarcillin component) every four hours* A third generation cephalosporin such as ceftriaxone 1 g IV every 24 hours PLUS Metronidazole 500 mg IV every eight hours A third generation cephalosporin such as ceftriaxone 100 mg/kg per dose every 24 hours* PLUS Metronidazole 10 mg/kg per dose every eight hours* COMPLICATIONS — The most serious complications of animal bites include trauma to deep structures, and infections, either transmitted or arising in the wound. In addition children who have suffered dog bites requiring at least minor surgical intervention may develop symptoms of post-traumatic stress disorder (PTSD) [40]. ■Systemic infections – Any infected bite wound can progress to infection of underlying structures (eg, bone, joint, tendon) and to bloodstream infection. Human bites can transmit numerous other infections, including hepatitis viruses B (HBV) and C (HCV), primary syphilis (rare), and herpes simplex virus [33,41]. The risk for transmitting HIV through saliva is extremely low but is of concern if there is blood in the saliva. Counseling regarding post-exposure HIV prophylaxis is appropriate in this setting [34]. (See "Management of healthcare personnel exposed to HIV".) Any patient negative for anti-HBs antibodies who is bitten by an individual positive for HBsAg should receive both hepatitis B immune globulin (HBIG) and hepatitis B vaccine (table 7). Individuals who work in facilities where the risk for human bites is high, such as institutions for the cognitively impaired, should be given the hepatitis B vaccine series upon employment. (See "Hepatitis B virus vaccination", section on 'Indications'.) ■Post-traumatic stress disorder – Children who have suffered dog bites requiring at least minor wound repair, particularly if the wounds are deep or multiple, may develop symptoms of post-traumatic stress disorder (PTSD) [40]. In one prospective study, the parents of 22 children who presented to an emergency department for minor surgical treatment of dog bites agreed to complete a questionnaire and undergo a telephone and/or personal interview about the circumstances of the injury and the child's behavior before and after it occurred. The interviews took place between two and nine months after the incident. Among the 22 children, 12 had symptoms of PTSD for at least one month (five children met all of the DSM-IV criteria and seven met only some) (table 8). SUMMARY AND RECOMMENDATIONS ■Most animal bites are caused by dogs, cats, and humans. The predominant organisms in animal bite wounds are the oral flora of the biting animal as well as human skin flora (such as Staphylococci and Streptococci). (See 'Epidemiology' above and 'Microbiology' above and "Soft tissue infections due to dog and cat bites" and "Soft tissue infections due to human bites".) ■The typical location and nature of the injury differs depending upon the animal inflicting the bite. (See 'Clinical manifestations' above.) Wound assessment ■After appropriate local anesthesia, the wound should be carefully explored to identify injury to underlying structures and the presence of a foreign body. Appropriate imaging should be obtained for deep bite wounds near bone and/or joints and when a foreign body is suspected (eg, plain radiograph or ultrasound). (See 'Plain radiographs and ultrasound' above and "Infiltration of local anesthetics" and "Topical anesthetics in children".) ■Head computed tomography is warranted in patients with a deep dog bite to the scalp, including puncture wounds, especially in children less than two years of age. (See 'Head computed tomography' above.) ■If a bite wound appears to be infected, Gram stain and aerobic and anaerobic cultures should be obtained prior to the initiation of antibiotics. Wound cultures are NOT indicated in clinically uninfected bite wounds as results do not correlate with the likelihood of infection or the pathogen that is present in patients with subsequent infection. (See 'Infected wound' above and 'Wound culture' above.) Wound management ■Wound irrigation and debridement of devitalized tissue are essential components in the initial management of bite wounds. The wound should be carefully explored to identify injury to underlying structures and the presence of a foreign body. (See 'Wound preparation' above and "Minor wound preparation and irrigation".) ■We suggest primary closure of open lacerations in healthy patients that meet all of the following criteria (Grade 2B): •Cosmetically important (eg, facial lacerations) •Wounds that are clinically uninfected •Wounds less than 12 hours old (24 hours on the face) •Wounds NOT located on the hand or foot ■Sealing the wound with cyanoacrylate tissue adhesive ("glue") should be avoided. (See 'Primary closure' above and 'Wound preparation' above.) ■We suggest NOT closing wounds at high risk for the development of infection including the following types of wounds (Grade 2C): •Crush injuries •Puncture wounds •Bites involving the hands or feet •Wounds more than 12 hours old (24 hours old on face) •Cat or human bites (except those to the face) •Bite wounds in compromised hosts (eg, immunocompromised, absent spleen or splenic dysfunction, venous stasis, diabetes mellitus [adults]) (see 'Primary closure' above) ■Tetanus and rabies prophylaxis should be provided as indicated. (See 'Tetanus and rabies prophylaxis' above.) ■Surgical consultation may be indicated in selected circumstances. (See 'Surgical consultation' above.) ■Patients who are discharged after initial care should follow-up with their primary care provider or other appropriate clinician within 48 to 72 hours to assess wound status. (See 'Follow-up care' above.) Antibiotic therapy ■Prophylaxis with oral antibiotics should be given for patient circumstances as outlined above (table 3 and table 4). (See 'Antibiotic prophylaxis' above and "Soft tissue infections due to dog and cat bites", section on 'Prophylaxis' and "Soft tissue infections due to human bites", section on 'Antibiotics'.) ■Patients with deep or severe wound infections are treated with intravenous rather than oral antibiotics (table 1 and table 2). (See 'Infected bites' above and 'Empiric antibiotic therapy' above and "Soft tissue infections due to dog and cat bites", section on 'Prophylaxis' and "Soft tissue infections due to human bites", section on 'Antibiotics'.) Virus transmission after human bite ■Any patient negative for anti-HBs antibodies who is bitten by an individual positive for HBsAg should receive both hepatitis B immune globulin (HBIG) and hepatitis B vaccine (table 7). (See 'Viral prophylaxis after human bites' above.) ■The risk for transmitting HIV through saliva is extremely low but is of concern if there is blood in the saliva. Counseling regarding post-exposure HIV prophylaxis is appropriate in this setting. (See 'Viral prophylaxis after human bites' above and "Management of healthcare personnel exposed to HIV".)