Sections View Full Chapter Figures Tables Videos Annotate Full Chapter Figures Tables Videos Supplementary Content + Download Section PDF Listen ++ For further information, see CMDT Part 30-05: Animal & Human Bite Wounds + Key Features Download Section PDF Listen +++ +++ Essentials of Diagnosis ++ Cat and human bites are more likely to become infected than dog bites Bites to the hand are of special concern because of the possibility of closed-space infection Antibiotic prophylaxis indicated for noninfected bites of the hand; hospitalization required for infected hand bites All infected wounds need to be cultured to direct therapy +++ General Considerations ++ Biting animals are usually known by their victims, and most biting incidents are provoked (ie, bites occur while playing with the animal or waking it abruptly from sleep) Important determinants of whether bites become infected Animal inflicting the bite Location of the bite Type of injury inflicted Bites on the extremities are more likely to become infected than bites on the head, face, and neck Failure to elicit a history of provocation is important, because an unprovoked attack raises the possibility of rabies Human bites Usually inflicted by children while playing or fighting In adults, bites are associated with alcohol use and closed-fist injuries that occur during fights Infections following human bites are variable Because bites inflicted by children are superficial, they rarely become infected Bites by adults become infected in 15–30% of cases, with a particularly high rate of infection in closed-fist injuries "Through and through" bites (eg, involving the mucosa and skin) have an infection rate similar to closed-fist injuries Cat bites More likely to become infected than human bites 30–50% of cat bites become infected Dog bites, for unclear reasons, become infected only 5% of the time Puncture wounds become infected more frequently than lacerations, probably because the latter are easier to irrigate and débride The bacteriology of dog and cat bites is polymicrobial Over 50% of infections are caused by aerobes and anaerobes 36% are caused by aerobes alone Pure anaerobic infections are rare Pasteurella species are the single most common pathogen—75% of cat bites and 50% of dog bites Other common aerobes include Streptococci Staphylococci Moraxella Neisseria Common anaerobes include Fusobacterium Bacteroides Porphyromonas Prevotella Human bites are a mixture of aerobes and anaerobes in 54% and aerobes alone in 44% Staphylococci and streptococci are the most common aerobes Eikenella corrodens (isolated in 30% of infections), Prevotella, and Fusobacterium are the most common anaerobes Although the above-named organisms are the most common, numerous others have been isolated such as Capnocytophaga (dogs and cats), Pseudomonas, and Haemophilus, emphasizing the need to culture all infected wounds to define microbiology HIV transmission following a bite has been rarely reported; saliva not contaminated with blood is very low risk +++ Demographics ++ About 1000 dog bite injuries require emergency department attention each day in the United States, most often in urban areas Dog bites occur most commonly in the summer months + Clinical Findings Download Section PDF Listen +++ +++ Symptoms and Signs +++ Dog and cat bites ++ Early infections (within 24 h after the bite) are characterized by Rapid onset and progression Fever Chills Cellulitis Local adenopathy +++ Human bites ++ Early infections can produce a rapidly progressive necrotizing infection Late infections (longer than 24 h after the bite) Present with local swelling and erythema Drainage and systemic symptoms may or may not be present + Diagnosis Download Section PDF Listen +++ +++ Laboratory Tests ++ Because the bacteriology of the infections is so variable, always culture infected wounds and adjust therapy appropriately, especially if the patient is not responding to initial empiric treatment +++ Imaging Studies ++ Radiographs should be obtained to look for fractures and the presence of foreign bodies + Treatment Download Section PDF Listen +++ +++ Medications +++ Prophylactic antibiotics ++ Prophylaxis is indicated in high-risk bites, eg, any cat bites and hand bites by any animal or by humans The drug of choice is amoxicillin-clavulanate 500 mg orally three times daily for 5–7 days For patients with serious allergy to penicillin, combination therapy is recommended: clindamycin 300 mg orally three times daily plus doxycycline 100 mg orally twice daily, or double-strength TMP-SMZ orally twice daily, or a fluoroquinolone (ciprofloxacin 500 mg orally twice daily or levofloxacin 500–750 mg orally once daily) for 5–7 days Moxifloxacin, 400 mg orally once daily for 5–7 days, may be suitable monotherapy alternative due to its mixed aerobic and anaerobic activity Immunocompromised and asplenic patients are at risk for developing overwhelming bacteremia and sepsis following animal bites and should also receive prophylaxis, even for low-risk bites +++ Antibiotics for Infected Wounds ++ Infected wounds require antibiotics, either orally or intravenously, depending on individualized clinical decisions Most common pathogens require either combination therapy with a β-lactam plus a β-lactamase inhibitor or a carbapenem Combination therapy with a β-lactam plus a β-lactamase inhibitor Ampicillin-sulbactam (Unasyn), 1.5–3.0 g intravenously every 6–8 hours Amoxicillin-clavulanate (Augmentin), 500 mg orally three times daily Carbapenem: Ertapenem, 1 g intravenously daily For patients with severe penicillin allergy, clindamycin (600–900 mg intravenously every 8 hours) plus a fluoroquinolone (ciprofloxacin, 400 mg intravenously every 12 hours; levofloxacin, 500–750 mg intravenously once daily) or TMP-SMZ (10 mg/kg of trimethoprim daily in two or three divided doses) Duration of therapy is usually 2–3 weeks unless complications are present If complications are present, extend therapy to 4–6 weeks +++ Therapeutic Procedures ++ Careful examination to assess the extent of the injury (tendon laceration, joint space penetration) is critical to appropriate care Vigorous cleansing and irrigation of the wound as well as débridement of necrotic material are the most important factors in decreasing the incidence of infections If wounds require closure for cosmetic or mechanical reasons, suturing can be done Never suture an infected wound, and wounds of the hand should generally not be sutured since a closed-space infection of the hand can result in loss of function + Outcome Download Section PDF Listen +++ +++ Prevention ++ All patients must be evaluated for the need for tetanus (Tables 30–7 and 33–2) and rabies prophylaxis (see Rabies) ++Table Graphic Jump LocationTable 30–7.Recommended adult immunization schedule—United States, 2020.View Table||Download (.pdf) Table 30–7. Recommended adult immunization schedule—United States, 2020. ++Table Graphic Jump LocationTable 33–2.Guide to tetanus prophylaxis in wound management.View Table||Download (.pdf) Table 33–2. Guide to tetanus prophylaxis in wound management. History of Absorbed Tetanus Toxoid Clean, Minor Wounds All Other Wounds1 Tdap or Td2 TIG3 Tdap or Td2 TIG3 Unknown or < 3 doses Yes No Yes Yes 3 or more doses No4 No No5 No 1Such as, but not limited to, wounds contaminated with dirt, feces, soil, saliva, etc; puncture wounds; avulsions; and wounds resulting from missiles, crushing, burns, and frostbite.2Td indicates tetanus toxoid and diphtheria toxoid vaccine, adult form. Tdap indicates tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis vaccine, which may be substituted as a single dose for Td. Unvaccinated individuals should receive a complete series of three doses, one of which is Tdap.3Human tetanus immune globulin, 250 units intramuscularly.4Yes if more than 10 years have elapsed since last dose.5Yes if more than 5 years have elapsed since last dose. (More frequent boosters are not needed and can enhance side effects.) Tdap has been safely administered within 2 years of Td vaccination, although local reactions to the vaccine may be increased. +++ Follow-Up ++ Careful follow-up is required every 1–2 days to assess improvement +++ Complications ++ Osteomyelitis Septic arthritis Tendon rupture Abscess +++ Prognosis ++ Generally good, but resolution may be slow, especially with Pasteurella infections +++ When to Refer ++ If septic arthritis or osteomyelitis is suspected For exposure to bites by dogs, cats, reptiles, amphibians, and rodents When rabies is a possibility +++ When to Admit ++ Patients with infected hand bites Deep bites, particularly if over joints + References Download Section PDF Listen +++ + +Bialasiewicz S et al. Rapid diagnosis of Capnocytophaga canimorsus septic shock in an immunocompetent individual using real-time Nanopore sequencing: a case report. BMC Infect Dis. 2019 Jul 24;19(1):660. [PubMed: 31340776] + +Bula-Rudas FJ et al. Human and animal bites. Pediatr Rev. 2018 Oct;39(10):490–500. [PubMed: 30275032] + +Dhillon J et al. Scoping decades of dog evidence: a scoping review of dog bite-related sequelae. Can J Public Health. 2019 Jun;110(3):364–75. [PubMed: 30378009] + +Kheiran A et al. Cat bite: an injury not to underestimate. J Plast Surg Hand Surg. 2019 Dec;53(6):341–6. [PubMed: 31287352] + +Kormondi S et al. Human pasteurellosis health risk for elderly persons living with companion animals. Emerg Infect Dis. 2019 Feb;25(2):229–35. [PubMed: 30666933]