INTRODUCTION — The evaluation and management of animal bite wounds will be discussed here.
Issues related to zoonoses from dogs and cats are found elsewhere. (See "Zoonoses: Dogs" and "Zoonoses: Cats" and "Capnocytophaga" and "Pasteurella infections" and "Microbiology, epidemiology, clinical manifestations, and diagnosis of cat scratch disease".)
Issues related to the evaluation and management of human bite wounds are discussed separately. (See "Human bites: Evaluation and management".)
EPIDEMIOLOGY — Animal bites are common worldwide and may be associated with significant morbidity. In North America, two to five million animal bites occur annually, which account for about 1 percent of emergency department visits and 10,000 inpatient admissions annually [1-3].
Dog bites account for approximately 90 percent of animal bites (rate of 103 to 118 per 100,000 population) [4]. Most dog bite victims are children, with the highest number in boys between five and nine years of age [5-9]. Fatalities are rare but disproportionately affect children younger than 10 years of age [10,11]. In resource-poor regions of the world, stray dog bites are an important cause of rabies transmission. (See "Clinical manifestations and diagnosis of rabies", section on 'Animal reservoirs'.)
Cat bites account for approximately 10 percent of animal bite wounds and occur most often in adult women [7]. Infections are more common after cat bites than dog bites [12,13]. For example, in one retrospective series including more than 2500 dog bites and almost 1000 cat bites, infection rates were 7 and 49 percent, respectively [12,13].
Factors that increase the risk of infection following an animal bite include [4,14]:
●Underlying immunosuppression (including diabetes)
●Bite involving the hand or foot
●Bite in an extremity with underlying venous and/or lymphatic compromise
●Bite near or in a prosthetic joint or vascular graft
●Crush injury or puncture wound
●Cat bite (given propensity for association with deep puncture wounds)
●Delayed presentation (≥12 hours after a bite on the extremities and ≥24 hours after a bite on the face)
MICROBIOLOGY — Relevant pathogens in the setting of animal bite wounds include the oral flora of the biting animal and human skin flora (such as staphylococci and streptococci) [15,16].
Important oral animal flora include:
●Pasteurella spp – Pasteurella species are isolated from 50 percent of dog bite wounds and 75 percent of cat bite wounds (picture 1) [15]. Pasteurella multocida are fastidious organisms and are often misidentified. The incubation period for P. multocida infection is one to three days. (See "Pasteurella infections".)
●Capnocytophaga spp – Capnocytophaga canimorsus can cause bacteremia and fatal sepsis after animal bites, especially in patients with asplenia, alcoholism, or underlying hepatic disease [17]. The incubation period for C. canimorsus infection is one to three days. (See "Capnocytophaga".)
●Bartonella henselae – B. henselae may be transmitted via the bite of an infected cat; other forms of transmission include cat scratches, flea exposure, and contact with cat saliva via broken skin or mucosal surfaces. The incubation period for B. henselae infection is 7 to 14 days. (See "Microbiology, epidemiology, clinical manifestations, and diagnosis of cat scratch disease".)
●Anaerobes – Anaerobes isolated from dog and cat bite wounds include Bacteroides species, fusobacteria, Porphyromonas species, Prevotella species, cutibacteria (formerly propionibacteria), and peptostreptococci [18].
The average bite wound culture yields five types of bacterial isolates [15]. Mixed aerobic and anaerobic bacteria are observed in 60 percent of cases; skin flora are isolated in about 40 percent of cases [15].
Specimens obtained at the time of debridement of infected wounds should be sent for aerobic and anaerobic bacterial cultures to identify the causative pathogen(s), prior to initiation of antibiotics. The laboratory requisition should note that an animal bite wound is the culture source, given the fastidious nature of P. multocida. (See 'Debridement' below.)
CLINICAL EVALUATION — Patients may seek care for evaluation of bite injury (in absence of infection) or established bite infection.
History and physical examination — The typical location and nature of bite injury differs depending upon the nature of the animal inflicting the bite.
●Dog bites – In young children, dog bites usually involve the head and neck [8,19]. In older children, adolescents and adults, dog bites usually involve the extremities, particularly the dominant hand [4,7].
Dog bites may be associated with a range of injuries, from minor wounds (eg, scratches, abrasions) to major wounds (eg, open lacerations, deep puncture wounds, tissue avulsions, and crush injuries) (picture 2) [7,20]. In particular, the jaws of large dogs, such as pit bull terriers, German shepherds, and Rottweilers can exert a strong force that may inflict serious injury and damage underlying structures [21,22].
In children, a dog bite to the head may penetrate the skull, resulting in depressed skull fracture, local infection, and/or brain abscess [23,24].
●Cat bites – Cat bites usually occur on the extremities [7]. Cat bite wounds tend to penetrate deeply with higher risk of deep infection (abscess, septic arthritis, osteomyelitis, tenosynovitis, bacteremia, or necrotizing soft tissue infection) than dog bites [7,25,26].
The physical examination should first ensure that the patient is hemodynamically stable and should assess for injuries to adjacent structures, especially for bites with deep puncture wounds on the head, neck, trunk, or close to joints. Bite wounds should be evaluated carefully for foreign material, and a neurovascular assessment should be performed in areas distal to the wound.
The likelihood of wound infection should be determined based upon physical findings. The median time to signs and symptoms of infection following a dog bite is approximately 24 hours; the median time to signs and symptoms of infection following a cat bite is typically shorter (ie, approximately 12 hours) and infections apparent within hours of a cat bite have been described [15].
Bite wound infection may be superficial (eg, cellulitis, with or without abscess) or deep (abscess, septic arthritis, osteomyelitis, tenosynovitis, or necrotizing soft tissue infection):
●Clinical manifestations of cellulitis include fever, tenderness, erythema, swelling, and warmth; purulent drainage and/or lymphangitis may be present (picture 3). An associated superficial abscess may present as a tender, erythematous, fluctuant nodule.
●In addition to the above manifestations, clues for deep infection include persistent or progressive pain several days following the initial injury, pain with passive movement, pain out of proportion to exam findings, crepitus, joint swelling, systemic illness (fever, hemodynamic instability), and persistent signs of infection despite initial wound care and antibiotic administration.
The level of suspicion for deep infection should be increased for patients with immunosuppression (including diabetes) or neuropathy; these patients often present later in their course with increased risk of serious infection and limited pain on clinical exam.
Clinical manifestations of wound infection and associated complications are described further separately. (See "Cellulitis and skin abscess: Epidemiology, microbiology, clinical manifestations, and diagnosis" and "Septic arthritis in adults" and "Nonvertebral osteomyelitis in adults: Clinical manifestations and diagnosis" and "Infectious tenosynovitis" and "Necrotizing soft tissue infections".)
Laboratory testing — Laboratory testing should be reserved for patients with infected bite wounds. In these patients, laboratory findings are nonspecific. Leukocytosis and elevated serum inflammatory markers may or may not be observed in patients with bite-associated infection.
Cultures from infected bite wounds should be obtained to establish the microbiology of the infection and to guide antibiotic therapy. Wound cultures are not indicated in clinically uninfected bite wounds because results do not correlate with subsequent infection [14,27].
Bacteremia may occur in the setting of superficial or deep infection. Blood cultures should be obtained in patients with fever or other signs of systemic infection and patients who are immunosuppressed [14,28]. In other patients, the yield of blood cultures is typically low and the risk of false positives likely outweighs the benefit.
Imaging — Imaging is not necessary for most clinically uninfected, superficial bites. Deep bite wounds, including those near joints warrant radiographs (anterior-posterior and lateral) to evaluate for evidence of foreign bodies (such as embedded teeth), fracture, or joint disruption.
In children <3 years with a dog bite to the scalp associated with a wound of uncertain depth, computed tomography (CT) of the head may be useful to evaluate for penetrating injury of the skull [24,29]. Radiographic findings may include skull fracture, puncture through the outer plate of the skull, and free air in the cranial vault.
In patients with clinical manifestations suspicious for superficial infection, plain radiographs as described above can help determine the depth of the wound and potential for infection of adjacent deep soft tissues, joints, or bone. In addition, bedside ultrasound can identify the presence of an abscess and facilitate drainage. (See "Techniques for skin abscess drainage", section on 'Bedside ultrasonography'.)
If there is concern for deeper infection (eg, pyomyositis or osteomyelitis), magnetic resonance imaging (MRI) is the optimal technique. CT may be used if MRI is not immediately available. Plain radiographs are warranted if other forms of imaging are not available (picture 4). Ultrasound may be useful for identifying deep abscess formation but does not facilitate evaluation of bony structures. (See "Pyomyositis", section on 'Radiography' and "Nonvertebral osteomyelitis in adults: Clinical manifestations and diagnosis", section on 'Radiography'.)
MANAGEMENT — Patients may seek care for evaluation of bite injury (in absence of infection) or established bite infection.
Life-threatening wounds — Deep wounds to vital structures should be treated as major penetrating trauma as discussed separately. (See "Approach to the initially stable child with blunt or penetrating injury", section on 'Penetrating trauma' and "Penetrating neck injuries: Initial evaluation and management" and "Severe lower extremity injury in the adult patient".)
Uninfected bite — For patients with an animal bite injury in the absence of clinical evidence for infection (on physical examination or imaging), components of management include wound care, foreign body removal (if present), and assessment of need for antibiotic prophylaxis, tetanus prophylaxis, and rabies prophylaxis [14,30].
Wound care
Preparation — Appropriate wound management is the most important factor for preventing infection in patients with animal bites [7].
Components of bite wound care include (see "Basic principles of wound management"):
●Control bleeding (direct pressure should be applied to actively bleeding wounds).
●Clean wound with soap and water, povidone iodine, or other antiseptic solution.
●Provide local anesthesia, followed by irrigation with sterile saline and removal of grossly visible debris. Clinically uninfected bite wounds should not be cultured; results are not predictive of subsequent infection [4,14]. (See "Subcutaneous infiltration of local anesthetics" and "Clinical use of topical anesthetics in children" and "Minor wound evaluation and preparation for closure".)
●Carefully re-examine the clean wound and determine whether wound closure is appropriate. (See 'History and physical examination' above and 'Closure' below.)
●Puncture wounds should not be closed; management of these wounds is discussed separately. (See "Infectious complications of puncture wounds", section on 'Management'.)
Closure — The decision to close a dog or cat bite laceration must weigh the benefit of enhanced cosmesis with the increased risk of infection associated with animal bites. Indications for surgical consultation are discussed below. (See 'Surgical consultation' below.)
We suggest that bite wounds be left open to heal by secondary intention (rather than closed primarily) in the following circumstances [14,31-34]:
●Crush injuries
●Puncture wounds
●Cat bite wounds (facial wounds are an exception; see below)
●Wounds involving the hands and feet (picture 3)
●Wounds ≥12 hours old (≥24 hours old on the face)
●Wounds in immunocompromised hosts (including diabetes)
●Wounds in patients with venous stasis
Wounds left open to heal by secondary intention should be debrided, irrigated copiously, dressed, and evaluated daily for signs of infection.
Primary closure is a reasonable alternative for simple lacerations due to dog bites on the face, trunk, arms, or legs. In addition, primary closure may be performed for lacerations caused by cat bites on the face, given the cosmetic importance of this region.
Lacerations closed primarily should be clinically uninfected and ideally <24 hours old (facial lacerations) or <12 hours old (sites other than the face) [35]. Meticulous debridement and copious irrigation should be performed prior to closure. Subcutaneous sutures should be avoided or used sparingly because foreign material in a contaminated wound increases the risk of infection [14]. Bite wounds should not be closed with tissue adhesive ("glue").
Antibiotic prophylaxis is suggested for all patients who undergo primary closure of a dog or cat bite. In addition, these patients warrant a wound check at 24 to 48 hours to assess for signs of infection. (See 'Antibiotic prophylaxis' below.)
Alternatively, the patient may be started on prophylactic antibiotics and return for delayed primary closure if no signs of infection are present after two to three days.
The Infectious Diseases Society of American (IDSA) recommends against primary closure of dog or cat bites, other than for facial lacerations; the face is an exception because it is cosmetically important and has a lower rate of infection relative to other areas, perhaps due to better blood supply [1].
In general, most experts favor forgoing primary closure of lacerations from cat bites in regions other than the face, in agreement with the IDSA. However, some experts favor pursuing primary closure of lacerations due to dog bites on the trunk, arms, or legs (though not on the hands or feet) [36,37]. The approach depends on individual circumstances including the nature of the wound, whether irrigation and debridement can reasonably clean the wound, and the immune status of the host.
Primary closure of simple lacerations after a dog bite is associated with an infection rate of 5 to 8 percent (with or without administration of prophylactic antibiotics); lacerations less than eight hours old or located on the face have a lower risk of infection [35-38]. In one small trial of dog bites, laceration closure was not associated with increased rate of infection when compared with healing by secondary intention [36]. In one series of 80 children with facial dog bite wounds managed with primary wound closure and prophylactic antibiotic treatment, no cases of infection were observed [39].
Surgical consultation — Surgical consultation is warranted in the following circumstances [33]:
●Complex facial lacerations (see "Assessment and management of facial lacerations")
●Deep wounds that penetrate bone, tendons, joints, or other major structures
●Wounds associated with neurovascular compromise
Antibiotic prophylaxis — In some circumstances, antibiotic prophylaxis is warranted for patients who present for evaluation of bite injury in the absence of signs or symptoms of infection.
Indications — We suggest antibiotic prophylaxis for patients with clinically uninfected wounds and any one of the following features that further raise the risk of infection [1,40-43]:
●Lacerations undergoing primary closure and wounds requiring surgical repair
●Wounds on the hand(s), face, or genital area
●Wounds in close proximity to a bone or joint (including prosthetic joints)
●Wounds in areas of underlying venous and/or lymphatic compromise (including vascular grafts)
●Wounds in immunocompromised hosts (including diabetes)
●Deep puncture wounds or laceration (especially due to cat bites)
●Wounds with associated crush injury
In the absence of the above factors, we do not favor use of antibiotic prophylaxis; however, some favor administration of antibiotic prophylaxis for animal bites that are older than eight hours [44]; the approach should be tailored to individual circumstances.
The above indications for antibiotic prophylaxis are supported by a prospective observational study including more than 400 patients with dog bites, and infection developed in 5 percent of cases; wounds at greatest risk of infection included puncture wounds and wounds closed during treatment [41]. Use of antibiotic prophylaxis is also based upon indirect evidence for a higher risk of wound infection in certain regions of the body such as the hands, feet, or genital area and in patients with poor circulation and immunocompromise.
In the absence of the above factors, the benefit of antibiotic prophylaxis appears to be marginal. In a meta-analysis including eight randomized trials of patients with dog bite wounds, the cumulative incidence of infection was 16 percent; the relative risk of infection in patients treated with antibiotics compared with controls was 0.6 (95% CI 0.4-0.8) [42]. A subsequent Cochrane review concluded that prophylactic antibiotics did not appear to reduce the rate of infection after bites by cats or dogs but did reduce the rate of infection following hand bites (odds ratio 0.1, 95% CI 0.0-0.9) [43].
Regimen — Antibiotic prophylaxis should include empiric coverage of the expected oral animal flora; appropriate agents are outlined in the table (table 1). These regimens also include reasonable coverage of methicillin-susceptible Staphylococcus aureus and streptococci. Patients who warrant antimicrobial prophylaxis should receive the first dose as soon as possible after the injury. (See 'Microbiology' above.)
Because of its spectrum of coverage, the preferred antibiotic agent for prevention of infection due to animal bite wounds is amoxicillin-clavulanate (table 1) [1].
Alternative prophylaxis regimens for patients unable to take amoxicillin-clavulanate should include an agent with activity against P. multocida and an agent with anaerobic activity; regimens and dosing are summarized in the table (table 1) [1,14,42,45,46].
Agents lacking in vitro activity against P. multocida should be avoided; these include first-generation cephalosporins (such as cephalexin), penicillinase-resistant penicillins (such as dicloxacillin), and macrolides (such as erythromycin) [47].
The duration of prophylactic oral antibiotics is three to five days with close follow-up [1]. Signs of infection on follow-up examination should prompt further evaluation (with radiographic imaging and/or surgical consultation, if needed), an extension of the antibiotic course, and/or a switch to intravenous therapy.
Infected bite — For patients with an animal bite and clinical evidence for infection (on physical examination and/or imaging), components of management include surgical consultation for selected patients as described below, debridement of infected tissue, foreign body removal (if present), obtaining wound cultures (and blood cultures in patients with immunocompromise or signs of systemic infection), administration of antibiotic therapy, and providing tetanus and rabies prophylaxis as needed [14,30].
Surgical consultation — Surgical consultation for bite-associated infection is warranted in the following circumstances [33]:
●Deep infection (abscess, septic arthritis, osteomyelitis, tenosynovitis, pyomyositis, or necrotizing soft tissue infection)
●Infection involving the hands or face
●Infection associated with neurovascular compromise
●Infection with associated foreign body requiring removal
●Infection in immunocompromised hosts (including diabetes) or patients with venous stasis
●Rapidly progressive infection
●Presence of crepitus
●Persistent signs and symptoms of infection despite appropriate antibiotic therapy
Debridement — Debridement of infected tissue is an important component of management for an infected bite. If previously repaired, suture material should be removed. Associated abscess(es) should be drained. (See "Techniques for skin abscess drainage".)
Specimens should be obtained at the time of debridement and prior to the initiation of antibiotics. They should be sent for aerobic and anaerobic bacterial cultures to identify the causative pathogen(s). The laboratory requisition should note that an animal bite wound is the culture source.
In general, infected bite wounds should be left open following debridement, with approximation of wound edges to facilitate closure by secondary intention. Primary closure is appropriate for facial wounds, large lacerations, and disfiguring wounds.
Antibiotic therapy — Antibiotic therapy should be administered to patients with suspected or known bite-associated infection, following collection of blood cultures and wound cultures.
Spectrum of therapy — Antibiotic therapy should include empiric coverage of the expected oral animal flora; appropriate agents are outlined in the tables (table 1 and table 2). These regimens include reasonable coverage of methicillin-susceptible S. aureus and streptococci. (See 'Microbiology' above and 'Antibiotic prophylaxis' above.)
For patients with risk factors for colonization with methicillin-resistant S. aureus (MRSA) (table 3), empiric antibiotic coverage for MRSA may be important. In addition, pets can become colonized with MRSA and transmit it via bites and scratches [48,49]. Issues related to risk factors and treatment of MRSA are discussed further separately. (See "Methicillin-resistant Staphylococcus aureus (MRSA) in adults: Treatment of skin and soft tissue infections" and "Methicillin-resistant Staphylococcus aureus (MRSA) in adults: Epidemiology".)
Route and duration of therapy — The route of antibiotic therapy should be based on individual clinical circumstances, such as severity of clinical presentation and patient comorbidities.
Treatment with parenteral antibiotics (table 2) is warranted in the following circumstances:
●Systemic signs of toxicity (eg, fever >100.5°F/38°C, hypotension, or sustained tachycardia)
●Deep infection (septic arthritis, osteomyelitis, tenosynovitis, bacteremia, or necrotizing soft tissue infection)
●Rapid progression of erythema
●Progression of clinical findings after 48 hours of oral antibiotic therapy
●Inability to tolerate oral therapy
●Proximity of the lesion to an indwelling device (eg, prosthetic joint or vascular graft)
The presence of an immunocompromising condition should lower the threshold for parenteral therapy.
If parenteral antimicrobial therapy is initiated, then a switch to oral treatment is reasonable once a clinical response to treatment is achieved.
Patients with superficial abscess (in the absence of bacteremia) who undergo drainage may be managed with initial parenteral antibiotic therapy until infection is resolving, followed by oral therapy to complete a course of 5 to 14 days [1]. Antibiotic therapy should be continued at least one to two days after signs and symptoms have resolved; this is typically less than seven days, but longer treatment may be needed if there is slow resolution of skin and soft tissue findings.
Patients with superficial wound infection (in the absence of abscess) and without signs of systemic infection may be managed with wound debridement and oral antibiotic therapy (table 1) to complete a course of 5 to 14 days with close outpatient follow-up; as mentioned above, a longer course of treatment is used in patients who have a slow response to treatment.
Antibiotic therapy should be tailored to culture and susceptibility data when available. Issues related to management of infection due to Pasteurella spp, Capnocytophaga spp, and B. henselae infection are discussed separately. (See "Pasteurella infections" and "Capnocytophaga" and "Treatment of cat scratch disease".)
In the setting of bacteremia, the approach to antibiotic therapy depends on the nature of the pathogen identified (see related topics).
Patients with complicated infections (such as tenosynovitis, septic arthritis, or osteomyelitis) require prolonged therapy tailored to individual circumstances [1]. (See "Infectious tenosynovitis" and "Septic arthritis in adults" and "Nonvertebral osteomyelitis in adults: Treatment".)
In patients with infection not requiring debridement or drainage, decisions regarding likely pathogens should be made based on the clinical history and patient risk factors. (See 'Microbiology' above.)
PREVENTING TETANUS AND RABIES — Tetanus immunization status should be determined in all patients with bite wounds and prophylaxis provided as needed. Animal bites are considered a tetanus-prone wound. Issues related to tetanus prophylaxis are summarized in the table (table 4) and discussed separately. (See "Tetanus-diphtheria toxoid vaccination in adults" and "Diphtheria, tetanus, and pertussis immunization in children 6 weeks through 6 years of age" and "Diphtheria, tetanus, and pertussis immunization in children 7 through 18 years of age".):
Bites, scratches, abrasions, or contact with animal saliva via mucous membranes or a break in the skin all can transmit rabies. For bites by potentially rabid animals, early and vigorous cleansing with soap and water and use of an antiseptic with activity against rabies virus (such as povidone iodine or 2% benzalkonium chloride) are important methods to decrease the risk of transmission in addition to timely administration of rabies immune globulin and vaccine [50-52]. (See 'Preparation' above.)
Issues related to rabies prophylaxis are summarized in the table and algorithm (table 5 and algorithm 1) and discussed further separately. (See "Indications for post-exposure and pre-exposure rabies prophylaxis" and "Rabies immune globulin and vaccine".)
UNUSUAL ANIMAL BITES — In general, the bites of small animals (such as squirrels, rodents, rabbits, and guinea pigs) should be treated in the same fashion as cat bites [53]. Antibiotic prophylaxis and empiric antibiotic therapy for infected bite wounds typically involves broad spectrum coverage of gram-positive, gram-negative, and anaerobic bacteria, similar to the spectrum for dog or cat bites.
In some instances, unique bite wound pathogens are identified (eg, Aeromonas species in alligator bites, Salmonella species in iguana bites, or Vibrio species in shark bites) [54-58]. Antimicrobial therapy should be guided by wound cultures results in consultation with an infectious disease specialist.
The United States Centers for Disease Control and Prevention provides guidance regarding the risk for rabies and the need for postexposure prophylaxis based on type of animal exposure.
COMPLICATIONS — Complications of animal bites include infection and trauma to deep structures. Fatal injuries associated with animal bites are rare; they usually occur in young children with injuries involving the head and neck or direct penetration of vital organs [10,59].
Children who have suffered dog bites may also develop symptoms of post-traumatic stress disorder [60]. (See "Posttraumatic stress disorder in children and adolescents: Epidemiology, pathogenesis, clinical manifestations, course, assessment, and diagnosis".)
SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Skin and soft tissue infections" and "Society guideline links: Rabies" and "Society guideline links: Dog and cat bites".)
INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5th to 6th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10th to 12th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.
Here are the patient education articles that are relevant to this topic. We encourage you to print or email these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)
●Beyond the Basics topics (see "Patient education: Animal and human bites (Beyond the Basics)" and "Patient education: Rabies (Beyond the Basics)")
SUMMARY AND RECOMMENDATIONS
●Frequency and complications
•Dog bites – These account for approximately 90 percent of animal bites and occur most often in children. They are associated with minor or major wounds and/or soft tissue infection. In children, dog bites usually involve the head and neck; in adolescents and adults, they usually involve the extremities. (See 'Epidemiology' above and 'History and physical examination' above.)
•Cat bites – These account for approximately 10 percent of animal bite wounds and happen most often in adult women. Cat bites usually occur on the extremities and have a much higher rate of infection (up to 50 percent) than dog bites. Because cat bites tend to penetrate deeply, deep infection is more common from cat bites (abscess, septic arthritis, osteomyelitis, tenosynovitis, bacteremia, or necrotizing soft tissue infection). (See 'Epidemiology' above and 'History and physical examination' above.)
●Physical examination of wound – Ensure that the patient is hemodynamically stable and assess for injuries to adjacent structures, especially for bites with deep puncture wounds on the head, neck, or trunk, or close to joints. Bite wounds should be evaluated carefully for foreign material, and a neurovascular assessment should be performed in areas distal to the wound. (See 'History and physical examination' above.)
●Diagnosis of infection – The likelihood of wound infection is based upon physical findings. Bite wound infection may be superficial (eg, cellulitis, with or without abscess) or deep (abscess, septic arthritis, osteomyelitis, tenosynovitis, or necrotizing soft tissue infection). (See 'History and physical examination' above.)
•Superficial infection – Clinical manifestations of superficial infection include fever, erythema, swelling, and warmth, purulent drainage, and/or lymphangitis. An associated superficial abscess may present as a tender, erythematous, fluctuant nodule.
•Deep infection – In addition to the above manifestations, clues for deep infection include persistent or progressive pain several days following the initial injury, pain with passive movement, pain out of proportion to exam findings, crepitus, joint swelling, systemic illness (fever, hemodynamic instability), and persistent signs of infection despite initial wound care and antibiotic administration. The level of suspicion for deep infection should be increased in patients with immunodeficiency (including diabetes mellitus) or neuropathy.
●Role of imaging – Imaging is not necessary for most clinically uninfected, superficial bites. Deep bite wounds, including those near joints warrant radiographs (anterior-posterior and lateral) to evaluate for evidence of foreign bodies (such as embedded teeth), fracture, or joint disruption. Selected patients with deep bite wounds or findings of deep infection may warrant advanced imaging such as computed tomography or magnetic resonance imaging. (See 'Imaging' above.)
●Management of uninfected bites – For patients with an animal bite injury in the absence of clinical evidence for infection (on physical examination or imaging), essential components of management include local wound care, foreign body removal (if present), and administration of antibiotic prophylaxis, tetanus prophylaxis, and rabies prophylaxis, as needed. (See 'Uninfected bite' above.)
•Wound management – We suggest that bite wounds be left open to heal by secondary intention (rather than closed primarily) in the following circumstances (Grade 2C) (see 'Closure' above):
-Crush injuries
-Puncture wounds
-Cat bite wounds (facial wounds are an exception)
-Wounds involving the hands and feet
-Wounds ≥12 hours old (≥24 hours old on the face)
-Wounds in immunocompromised hosts (including diabetes)
-Wounds in patients with venous stasis
Primary closure is a reasonable alternative for simple lacerations due to dog bites on the face, trunk, arms, or legs. In addition, primary closure may be performed for lacerations caused by cat bites on the face, given the cosmetic importance of this region. Lacerations closed primarily should be clinically uninfected and ideally <24 hours old (facial lacerations) or <12 hours old (sites other than the face).
•Indications for surgical consultation – These include complex facial lacerations, deep wounds, and neurovascular compromise. (See 'Surgical consultation' above.)
•Indications for prophylactic antibiotics – We suggest administering antibiotic prophylaxis for patients with uninfected bite wounds in the following circumstances (table 1) (Grade 2C):
-Wounds closed primarily and wounds requiring surgical repair
-Wounds on the hand(s), face, or genital area
-Wounds in close proximity to a bone or joint (including prosthetic joints)
-Wounds in areas of underlying venous and/or lymphatic compromise (including vascular grafts)
-Wounds in immunocompromised hosts (including diabetes)
-Deep puncture wounds or laceration (especially due to cat bites)
-Wounds with associated crush injury
Amoxicillin-clavulanate is the preferred agent for prophylaxis; dosing and alternative regimens are summarized in the table (table 1). (See 'Antibiotic prophylaxis' above.)
•Rabies and tetanus prophylaxis – Issues related to tetanus and rabies prophylaxis are summarized above and in the tables (table 4 and table 5). (See 'Preventing tetanus and rabies' above.)
●Management of infected bites
•Wound debridement – Debridement of infected tissue and abscess fluid (ie, source control) is a cornerstone of management. Surgical consultation is indicated in selected cases. In general, infected bite wounds are left open after debridement, except for facial wounds, large lacerations, and disfiguring wounds. Wound specimens should be obtained for culture. (See 'Debridement' above and 'Surgical consultation' above.)
•Antibiotic selection – Antibiotic regimens should cover the oral flora of the biting animal (such as Pasteurella spp, Capnocytophaga spp, and anaerobes) as well as human skin flora (such as staphylococci and streptococci). (See 'Microbiology' above and 'Spectrum of therapy' above.)
-Oral antibiotics – Oral antibiotics are often adequate, and amoxicillin-clavulanate is the preferred agent; dosing and alternative regimens are summarized in the table (table 1). (See 'Antibiotic therapy' above.)
-Indications for parenteral antibiotics – Treatment with parenteral antibiotics is warranted in certain circumstances, such as deep or rapidly progressive infection or systemic toxicity. Ampicillin-sulbactam is a favored agent; other agents and dosages are listed in the table (table 2). (See 'Antibiotic therapy' above and 'Route and duration of therapy' above.)
-Duration of therapy – Superficial infections typically require 5 to 14 days of antimicrobial therapy. Deeper or complication infections often require longer durations, based on the underlying infectious process. (See 'Route and duration of therapy' above.)
•Rabies and tetanus prophylaxis – Issues related to tetanus and rabies prophylaxis are summarized above and in the tables (table 4 and table 5). (See 'Preventing tetanus and rabies' above.)
