Mammalian Bites138. Ashley Booth Norse SECTION XIV BITES, STINGS, AND INJURIES FROM ANIMALS EPIDEMIOLOGY PATHOPHYSIOLOGY

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1 SECTION XIV BITES, STINGS, AND INJURIES FROM ANIMALS Mammalian Bites138 Ashley Booth Norse KEY POINTS Human bites, especially clenched-fist injuries (i.e., fight bites ) commonly cause septic joints, osteomyelitis, tenosynovitis, and fractures. Wound infections caused by human bites are usually polymicrobial. Pasteurella species are the most common organisms present in infected wounds from cat and dog bites. Injury to deeper structures should be suspected with all mammalian bites, and radiography should be considered to look for fractures, retained foreign bodies, gas in tissues, and osteomyelitis. EPIDEMIOLOGY Two to 4 million cat, dog, and human bites are reported by the Centers for Disease Control and Prevention every year, as well as approximately 300,000 emergency department (ED) visits secondary to mammalian bites. The exact number of mammalian bites is difficult to determine because many cases are not reported. Although dog bites outnumber cat bites, 20% to 80% of cat bites become infected, whereas just 3% to 18% of dog bites will become infected. 1-4 PATHOPHYSIOLOGY Wound infections from mammalian bites have a complicated microbiology profile. The majority of infections are polymicrobial with a mix of aerobic and anaerobic bacteria. Patients with acute cat bites (<24 hours from the time of the bite) most often have wound cultures that grow Pasteurella organisms, especially Pasteurella multocida. Patients with subacute cat bites (>24 hours) or who return to the ED more than 24 hours after initial treatment of an acute bite typically have cultures that grow mixed aerobic and anaerobic species, with Pasteurella, Staphylococcus, and Streptococcus species being the predominant pathogens. Other pathogens include the aerobe Moraxella and the anaerobes Fusobacterium, Bacteroides, and Porphyromonas. 2,3,5,6 Dog bites are the most common mammalian bites seen in the ED. Dog bites tend to cause more damage, injure deeper structures, and crush tissues because of the animal s powerful jaws, which can exert a pressure of 200 to 450 psi when biting. 1 Damage to deeper structures is more common with police dogs. 2 Dogs trained specifically for guard duty or for fighting, such as pit bulls, rottweilers, German shepherds, and chows, tend to cause a disproportionate number of bites resulting in serious injury and death. 2 Current research reveals that Pasteurella species are the most common organisms present in culture isolates from infected dog bite wounds, most frequently Pasteurella canis. 3 Other common aerobic pathogens in infected dog bite wounds include Staphylococcus and Streptococcus species. 2,3,5 Aerobes less frequently associated with cat and dog bite wound infections include Moraxella and Neisseria. Causative anaerobic organisms include Fusobacterium, Bacteroides, Porphyromonas, Prevotella, and Capnocytophaga. Capnocytophaga canimorsus causes an opportunistic infection that can result in severe infection and sepsis in immunocompromised patients. Mortality in patients with C. canimorsus infection approaches 30%. 3,6 When compared with cat bite victims, patients with dog bites tend to be seen later after injury but have a lower infection rate. Conversely, patients whose injuries become infected secondary to cat bites tend to seek treatment earlier than those with infected dog bite wounds, at a mean time of 12 hours. 1 It is speculated that the infection rate is higher because wounds from cats are more likely to be punctures, involve the hand, and become infected with Pasteurella species. 1,2 Human bites have long been associated with high rates of infection and complications such as septic joints, osteomyelitis, tenosynovitis, and fractures. However, recent studies show that human bites do not have a higher rate of infection than other bite wounds do. 1,2,5 Human bites can be divided into two categories. The first category is referred to as occlusional bites, defined as intentional bites in which the teeth actually close down on the victim s skin. The second category is referred to as clenchedfist injuries (also called fight bites ); these bites occur when the teeth hit or puncture the dorsum of the metacarpophalangeal region of a clenched hand. Clenched-fist injuries have a high propensity for causing injury to deep structures of the hand. Open fractures, joint involvement, and tendon injuries are common. Human bites to the hand, especially clenchedfist injuries, are at high risk for infection. 2,4,5 1187

2 SECTION XIV BITES, STINGS, AND INJURIES FROM ANIMALS Table Pathogens in Mammalian Bites MAMMALIAN BITE <24 HOURS >24 HOURS Human Polymicrobial: Streptococcus spp., 60-80% Staphylococcus spp., 37-46% Anaerobic spp., 44-60% (specifically Eikenella corrodens, 20-25%) Mixed aerobic and anaerobic Staphylococcus spp., Streptococcus spp. Cat Pasteurella spp. Mixed aerobic and anaerobic Pasteurella spp. Staphylococcus spp. Streptococcus spp. Dog Pasteurella spp. Mixed aerobic and anaerobic Pasteurella spp. Staphylococcus spp. Streptococcus spp. Wound infections caused by human bites are usually polymicrobial. Streptococci are present in 60% to 80% of isolates. Staphylococcus aureus is found in 37% to 46% of isolates, and anaerobic species are present in 44% to 60% of isolates, specifically Eikenella corrodens (20% to 25%). Herpes simplex virus can also be transmitted through infected saliva and can cause herpetic whitlow, as well as wound infections (Table 138.1). 2 PRESENTING SIGNS AND SYMPTOMS A thorough history should be obtained (Fig ), including the timing of the bite incident, the circumstances surrounding the bite, and whether a report was filed with animal control officials. If the victim knows the animal, it may be possible to ascertain the immunization status of the bite source and whether the animal is going to be quarantined to observe for signs of rabies. This information is especially important if the bite was unprovoked, if the animal was acting abnormally, or if the bite was caused by a wild animal. The patient s medical history (including a history of allergies, current medications, and immunization status) should also be obtained. Patients with human bites, especially clenched-fist injuries, may not be forthcoming about how their injury occurred. If the wound is on the extensor surface of the metacarpophalangeal joint, the patient should be treated as though the wound is a human bite. In patients with human bites, it is important to ascertain the human immunodeficiency virus (HIV) and hepatitis status of both the patient and the attacker. In major cases in which a patient suffers extensive injury, resuscitation from traumatic injury may be needed. Injury to deep structures, including major organs, and extensive blood loss are possible. It is usually apparent that a large animal has attacked the victim, but injuries from falls or other associated trauma can occasionally be occult. Disciplined, thorough evaluation of the patient s physical condition is warranted when associated injury may have occurred, especially since bite wounds draw the clinician s attention. DIFFERENTIAL DIAGNOSIS AND MEDICAL DECISION MAKING Vital signs should be determined in all patients with bites because hypotension or tachycardia may be a sign of blood loss and fever may be a sign of infection. All bites mandate a full neurovascular examination, including a thorough motor and sensory examination distal to the bite, as well as evaluation of all the tendons and ligaments in the region of the bite. The physical examination should also include a thorough vascular examination and evaluation of any compartments involved. RED FLAGS Emergency medical physicians must have a high level of suspicion with mammalian bites. For clenched-fist injuries, a high index of suspicion should be maintained for tendon injuries, as well as for open fracture and open joints. The metacarpophalangeal joint and extensor tendons are covered by a thin layer of skin when the hand is clenched, and tendons can often retract proximally when the hand is unclenched and the fingers extended. All bite wounds should undergo high-pressure irrigation of the wound with normal saline, dilute povidone-iodine solution, or poloxamer 188 (Shur-Clens). Explore all wounds. Extend the margins of deep puncture wounds or small laceration so that all possible injured structures can be visualized if possible injury to deeper structures is suspected. Radiography, angiography: If there is risk for a retained foreign body such as a tooth If there is risk for injury to deep structures such as a fracture If the patient has signs of infection (to look for retained foreign bodies, gas in tissues, and osteomyelitis) If a vascular injury is suspected, angiography may be needed to localize the injury or to determine the extent of the injury TREATMENT All bite wounds should undergo high-pressure irrigation of the wound with normal saline, dilute (<1%) povidone-iodine solution, or poloxamer 188 (Shur-Clens) (Table 138.2). Recent studies have looked at the efficacy of tap water as an irrigation solution 2,7 ; however, because no conclusive data exist at present for bite wounds, use of tap water as an irrigation solution for bite wounds cannot be supported at this time. Patients with larger or more complicated wounds may need to be anesthetized with lidocaine, bupivacaine, or another 1188

3 CHAPTER 138 Mammalian Bites PRIORITY ACTIONS Important Historical Questions to Ask Is the bite more or less than 12 hours old? Are you familiar with the animal or the owner of the animal that bit you? Was the bite provoked or unprovoked? Was a report filed with animal control or police? What is the immunization status of the bite source? Is the animal being watched or can it be watched for the next 10 days for signs of rabies? Do you have any other medical problems (especially diabetes, human immunodeficiency virus infection, acquired immunodeficiency syndrome, transplantation history)? Are you taking any medications such as steroids or immunosuppressive agents? Are you allergic to any medications? When was your last tetanus shot? Have you had three doses of tetanus vaccine? Have you ever had the rabies vaccine? History Physical examination Radiography Anesthesia Irrigation Exploration Débridement Specialist consultation if needed Primary closure if needed/appropriate anesthetic agent before irrigation and exploration of the wound. Epinephrine should be avoided if the bite involves the fingers, toes, nose, ears, or penis. 2 All wounds should be explored for foreign bodies and injuries to deeper structures such as arteries, nerves, tendons, and ligaments. All tendons in the injured area should be isolated and tested through their full range of motion to assess for partial lacerations or tears, especially if the hands or feet are involved. Any devitalized tissue or ragged edges should be débrided. There is no clear evidence whether suturing bite wounds increases the risk for infection, nor are there conclusive data on which wounds can safely be sutured. The safest course of action is to leave most bite wounds open and have the patient return for delayed primary closure if the wound does not become infected; however, primary closure may be necessary for cosmetic or functional reasons. Recent studies show that the infection rate of sutured bite wounds may initially be lower in certain circumstances than historically predicted. Primary closure may be safe for simple bite wounds less than 6 hours old that involve the trunk and extremities (with the exception of the hands and feet) and for simple bite wounds involving the face and neck that are less than 12 hours old. 1,2 The emergency physician should leave wounds open or consider closure by secondary intention for all infected wounds and all wounds at increased risk for infection, such as puncture wounds, hand and foot wounds, clenched-fist injuries, full-thickness wounds, wounds requiring débridement, wounds in patients older than 50 years or immunocompromised patients, wounds more than 12 hours old, and wounds involving damage to deep structures such as bones, joints, tendons, nerves, and blood vessels. Extremity wounds should be splinted and elevated. 2 All patients sustaining mammalian (cat, dog, human, primate) bites should be given a dose of tetanus immune globulin and a dose of tetanus toxoid if they have never had Splint and elevate extremity bites Oral or IV antibiotics if needed Tetanus booster/ immune globulin Rabies vaccine/ immune globulin HIV/hepatitis prophylaxis Discharge versus admission Wound recheck in 24 hours Fig Algorithm for the management of human, cat, and dog bites. HIV, Human immunodeficiency virus; IV, intravenous. the tetanus vaccine series or if they have not had three doses of tetanus toxoid. Patients who have had a full course of the tetanus vaccine series should be given a tetanus toxoid booster of 0.5 mg intramuscularly if more than 5 years has elapsed since the previous tetanus booster. 1189

4 SECTION XIV BITES, STINGS, AND INJURIES FROM ANIMALS Table Treatment of Mammalian Bites TYPE WOUND CARE ANTIBIOTIC PR. TETANUS PR. RABIES PR. HIV PR. HEPATITIS PR. Human High-pressure irrigation of the wound with normal saline or dilute (<1%) povidone-iodine solution; débride devitalized tissue or ragged edges Amoxicillin-clavulanate, second-generation cephalosporin with anaerobic activity, penicillin plus dicloxacillin, clindamycin plus ciprofloxacin or trimethoprimsulfamethoxazole Tetanus immunoglobulin (250 units IM) and tetanus toxoid (0.5 mg IM) if never had a tetanus vaccine or have not had 3 doses of tetanus toxoid; tetanus toxoid (0.5 mg IM) if >5 yr since previous tetanus booster None HAART therapy started within the first hr and continued for 28 days or bite source tested HIV negative; refer to the hospital for the specific drugs used in HAART therapy HBIG (0.06 ml/ kg IM); HBV given at separate site from HBIG Cat High-pressure irrigation of the wound with normal saline or dilute (<1%) povidone-iodine solution; débride devitalized tissue or ragged edges Amoxicillin-clavulanate, second-generation cephalosporin with anaerobic activity, penicillin plus a first-generation cephalosporin, clindamycin plus a fluoroquinolone or trimethoprimsulfamethoxazole Tetanus immune globulin (250 units IM) and tetanus toxoid (0.5 mg IM) if never had a tetanus vaccine or have not had 3 doses of tetanus toxoid; tetanus toxoid (0.5 mg IM) if >5 yr since previous tetanus booster HRIG (20 IU/kg) injected IM and/or around the bite site; rabies vaccine (1 ml IM) given in the deltoid in adults and in the thigh in children, on days 0, 3, 7, 14, and 28 None None Dog High-pressure irrigation of the wound with normal saline or dilute (<1%) povidone-iodine solution; débride devitalized tissue or ragged edges Amoxicillin-clavulanate, second-generation cephalosporin with anaerobic activity, penicillin plus a first-generation cephalosporin, clindamycin plus a fluoroquinolone or trimethoprimsulfamethoxazole Tetanus immune globulin (250 units IM) and tetanus toxoid (0.5 mg IM) if never had a tetanus vaccine or have not had 3 doses of tetanus toxoid; tetanus toxoid (0.5 mg IM) if >5 yr since previous tetanus booster HRIG (20 IU/kg) injected IM and/or around the bite site; rabies vaccine (1 ml IM) given in the deltoid in adults and in the thigh in children, on days 0, 3, 7, 14, and 28 None None HAART, Highly active antiretroviral therapy; HBIG, hepatitis B immune globulin; HBV, hepatitis B vaccine; HIV, human immunodeficiency virus; HRIG, human rabies immune globulin; IM, intramuscularly; Pr., prophylaxis. 1190

5 CHAPTER 138 Mammalian Bites Patients who sustain dog, cat, or other animal bites should be evaluated for the potential need for rabies vaccination (see Chapter 179). Patients who sustain high-risk bites in which the animal cannot be quarantined should receive 20 IU/kg of human rabies immunoglobulin (HRIG) injected around the bite site or intramuscularly (or both) and 1 ml of rabies vaccine administered intramuscularly either in the deltoid in adults or in the thigh in children on days 0, 3, 7, 14, and 28. HRIG and rabies vaccine should be injected at separate sites if both are administered intramuscularly. 8 Transmission of HIV and hepatitis B and C virus in human bites has been reported. 9 Patients who sustain human bites need to be evaluated and counseled about HIV and hepatitis B postexposure prophylaxis (PEP) (PEP for hepatitis C does not exist). HIV PEP should be started as soon as possible within the first 48 to 72 hours after a high-risk bite and continued for 28 days. High-risk bites are those in which the assailant is known to be HIV or hepatitis positive (or both) and bites in which blood exposure is involved. Hepatitis B PEP should include hepatitis B immune globulin (HBIG) and hepatitis B vaccine (HBV) if the patient has not previously been immunized. If the patient had previously received the hepatitis B vaccination series, a titer for anti-hbv should be drawn. If the patient has hepatitis B antibodies, no treatment is needed; if there are insufficient antibodies (anti-hbv < 10 miu/ml), the patient needs HBIG and an HBV booster. 9 Clinical evidence is limited on which cat and dog bites should receive prophylactic antibiotics. Cat bites especially puncture wounds, wounds involving the hand and feet, wounds involving deeper structures, wounds in immunocompromised patients, and wounds closed primarily are considered highrisk bites, and the patient should receive prophylactic antibiotics. Prophylactic antibiotics for cat and dog bites, specifically those seen within the first 24 hours, should cover Pasteurella, Staphylococcus, Streptococcus, and anaerobic species. Options include amoxicillin-clavulanate, a second-generation cephalosporin with anaerobic activity, and penicillin plus a first-generation cephalosporin. Clindamycin plus a fluoroquinolone or trimethoprim-sulfamethoxazole may be used in penicillin-allergic patients. Doxycycline plus metronidazole can also be used in penicillin-allergic patients. Human bites are also considered high-risk bites. Prophylactic antibiotics should be considered for bites extending through the dermis, bites closed primarily, bites with significant crush injury or requiring considerable débridement, puncture wounds, bites in elderly or immunocompromised patients, and bites that involve the hands, feet, or deeper structures. Human bite prophylaxis should cover Staphylococcus, Streptococcus, and anaerobes, including E. corrodens. Amoxicillin-clavulanate or penicillin plus dicloxacillin may be used. Clindamycin plus ciprofloxacin or trimethoprimsulfamethoxazole may be used in penicillin-allergic patients. FOLLOW-UP, NEXT STEPS IN CARE, AND PATIENT EDUCATION Wounds with significant tissue loss may need plastic surgery or hand surgery consultation for skin grafting, depending on the location of the bite. Specialty consultation is also mandated for any hand or foot wound that involves a joint, tendon, artery, or nerve. Most patients can be discharged home safely with follow-up or recheck in the ED, or both. SUGGESTED READINGS Broder J, Jerrard D, Olshaker J, et al. Low risk of infection in selected human bites treated without antibiotics. Am J Emerg Med 2004;22:10-3. Eilbert W. Dog, cat and human bites: providing safe and cost-effective treatment in the ED. Emerg Med Pract 2003;5:1-20. Griego R, Rosen T, Orengo IF, et al. Dog, cat and human bites: a review. J Am Acad Dermatol 1995;33: Oehler R, Velez A, Mizrachi M, et al. Bite-related and septic syndromes caused by cats and dogs. Lancet 2009;9: REFERENCES References can be found on Expert

6 CHAPTER 138 Mammalian Bites REFERENCES 1. Broder J, Jerrard D, Olshaker J, et al. Low risk of infection in selected human bites treated without antibiotics. Am J Emerg Med 2004;22: Eilbert W. Dog, cat and human bites: providing safe and cost-effective treatment in the ED. Emerg Med Pract 2003;5: Talan D, Citron D, Abrahamiam FM, et al. Bacteriologic analysis of infected dog and cat bites. N Engl J Med 1999;340: Griego R, Rosen T, Orengo IF, et al. Dog, cat and human bites: a review. J Am Acad Dermatol 1995;33: Brook I. Microbiology and management of human and animal bite wound infections. Prim Care Clin Office Pract 2003;30: Oehler R, Velez A, Mizrachi M, et al. Bite-related and septic syndromes caused by cats and dogs. Lancet 2009;9: Bansal BC, Wiebe RA, Perkins SD, et al. Tap water for irrigation of lacerations. Am J Emerg Med 2002;20: Centers for Disease Control and Prevention. Human rabies prevention practices United States Available at mmwrhtml/ htm. 9. Centers for Disease Control and Prevention. Antiretroviral postexposure prophylaxis after sexual, injection-drug use, or other nonoccupational exposure to HIV in the United States Available at mmwrhtml/rr5402al.htm e1