Management of Human and Animal Bite Wounds

An Overview

Bite Wounds

• Serious infections can result from wounds that are caused by bites from animals and humans

• Organisms recovered from bite wounds generally originate from the oral cavity of the biting animal, as well as from the patient's skin flora

Bite Wounds

• Anaerobes have been isolated from animal and human bite wound infections, especially those associated with abscess formation

• Common complications: – lymphangitis, septic arthritis, tenosynovitis, and osteomyelitis

• Uncommon complications: – endocarditis, meningitis, brain abscess, and sepsis

Bite Wound Overview• >1 million animal bites occur in the United States each year• Dog bites account for 80% to 90% of all bite wounds • Incidence of dog bites is higher in young children than in

adults• The bites in children frequently involving the head, face, or

neck• 4% of patients seen in the ED for a dog-bite wound require

hospitalization• 2% to 20% of dog-bite wounds become infected• Each year, more than a dozen deaths are caused by dog

bites

Bite Wound Overview

• Cat bites account for 5% to 15% of bite wounds• >½ occur in adults, and cat bites are more common

in women• Cat bites are almost always puncture wounds, and

the rate of infection is estimated to be 30% to 80%

Bite Wound Overview

• Human bites account for 2% to 3% of all reported bites with ¾ caused by aggressive acts

• Are either occlusional, usually seen in a sexual crime or child abuse, or clenched fist, usually the result of punching a person in the mouth

• An estimated 10% to 50% of human-bite wounds become infected

Microbiology (General)

• Streptococcus pyogenes has been found in human bites

• Pasteurella multocida in animal bites (60% of bacteremia cases) with Pasteurella septica causing central nervous system symptoms

• Eikenella corrodens in both animal and human bites (although predominantly in human bites)

Microbiology

• Dog bites: Capnocytophaga canimorsus (formerly CDC group DF-2), Capnocytophaga cynodegmi, Neisseria weaveri (formerly M-5), Weeksella zoohelcum (formerly IIj), Neisseria canis, Staphylococcus intermedius, NO-1, and EO-2.

• Pig bite: Flavobacterium IIb-like organisms • Horse and sheep: Actinobacillus species

Microbiology

• Marine setting: Vibrio species, Plesiomonas shigelloides, Aeromonas hydrophila, and Pseudomonas species

• Serious infections: tularemia (cats), herpes B virus (monkeys), rat-bite fever or sodoku (rats), hepatitis B virus (humans), leptospirosis (dogs and rodents), and rabies (dogs and other mammals)

Microbiology

• Human Bites: Staphylococcus aureus, Penicillin-resistant Gram-negative rods, alone or in mixed cultures, have been reported in 24% to 43% of cultured human bite wounds, anaerobic bacteria have been recovered from human bites in adults and children (50%)

Microbiology

• Predominant isolates were anaerobic Gram- negative bacilli: Prevotella, Porphyromonas species, Bacteroides species, Fusobacterium nucleatum, and anaerobic Gram-positive cocci

• Predominant aerobes: S aureus, group A beta- hemolytic streptococci, and E corrodens

Microbiology

• Common isolates: Streptococcus anginosus (52%), S aureus (30%), E corrodens (30%), F nucleatum (32%), and Prevotella melaninogenica (22%)

• Many Prevotella and S aureus strains were beta- lactamase producers

Microbiology

• Candida species were found in 8% of wounds, with Fusobacterium, Peptostreptococcus, and Candida species isolated more frequently from occlusional bites than from clenched-fist injuries

• Normal oral flora, rather than skin flora, to be the source of most bacteria isolated from human bite wound cultures

Signs/Symptoms• Signs and symptoms that emerge following a bite

depend on the type of animal inflicting the injury– immediate local or systemic symptoms can be severe following

bites by venomous animals (e.g., snakes, lizards, spiders)– Human bites and dog bites can develop infection rapidly because of

direct inoculation of oral and skin flora into the wound• Human bites are typically more serious than animal bites, particularly

clenched-fist injuries

– Eschariform lesions in persons appearing to be ill may suggest the

presence of C canimorsus infection

Signs/Symptoms

With a clenched-fist injury:– Teeth can cause deep lacerations that implant oral and skin

organisms into the joint capsules or dorsal tendons, which may cause septic arthritis or osteomyelitis

– Medical status of the source of the human bite (e.g., hepatitis, HIV, other transmittable diseases

– Radiographs are recommended for this type injury

– sedimentation rate or C-reactive protein level can help

Signs/Symptoms

Dog Bites:• 2% to 5% of all typical dog bite wounds become infected• The dog's rabies status needs to be ascertained• Gram's stain and culture for both aerobic and anaerobic bacteria

should be obtained from human and animal bite wounds • Wounds contaminated by soil or vegetative debris should be

cultured for mycobacterium and fungi

Management

Good wound management includes:• Evaluation• Proper local care• Antimicrobial agents• An incident of an animal bite should be reported to the local health

authorities

ManagementEvaluation:• Patient's medical history (e.g., current medications, splenectomy,

mastectomy, allergies, chronic disease, immunosuppression) • Type of attack (e.g., type of animal, provoked or unprovoked)• Examining the wound and related structures (eg, odor, depth, type,

and location; range of motion; joint involvement; edema; nerve and tendon damage; and presence of infection)

• Obtaining wound cultures and X-rays (when bone penetration is suspected)

• Determining wound approximation

ManagementLocal Care:• Cleansing- soap or a quaternary ammonium compound and water• Exploration- for damage to tissue caused by crushing or tearing with X-ray

examination for fractures and foreign bodies should be done when feasible• Irrigation- 150mL or more of NSS or lactated Ringer's solution• Debridement- Devitalized tissue should be removed• Drainage- TLS or JP drain system • Suturing- Controversy still exists as to whether clinically uninfected bite wounds

that have been seen within 24 hours should be surgically closed but the guideline is that puncture wound margins should be excised and left open after irrigation, and margins of other wounds should be excised and primary closure performed, with or without drainage

– Delayed primary closure or edge approximation should be done in wounds associated with crush injuries, preexisting edema, and injuries to the hands and feet.

Gory Pictures

Gory Pictures

Management• Monkeys may carry B virus, so wounds should be thoroughly cleansed and

irrigated for at least 15 minutes, and viral cultures should be performed after cleansing. Serum for acute viral B virus-specific serology should be stored at - 20°C and compared with a second sample obtained 21 days later. Antiviral therapy with acyclovir, valacyclovir, or famciclovir should be given to those persons with moderate- or high-risk wounds

• Hand bites are at high-risk of deep damage and severe infection. For human bites, the wounds should be opened, debrided, and thoroughly irrigated; primary closure and tendon and nerve repair should be delayed. Dog bites can be considered clean following debridement and irrigation, and primary closure can be performed

• In severe cases, hospitalization may be necessary, with immobilization by splinting or bulky dressings and elevation. Rabies prevention-including hyperimmune serum and active immunization-should be given after dog bites as indicated

Management• Facial bites, especially those in children, require meticulous

management. Most patients do well with careful debridement, ample irrigation and cleansing, and loose closure by suture. Close follow-up is required for at least 5 days. Because subsequent plastic reconstruction may be needed, it may be useful to consult with a plastic surgeon at the time of initial repair.

• Early management of all human bites, especially those to the hand, must be thorough and vigorous. Clenched-fist injuries require more intensive care, preferably by a hand surgeon, to evaluate the seriousness of injury to tendon, sheath, joint, joint capsule, and bone.

ManagementAntimicrobials:• Tetanus toxoid booster if adequately immunized in the past, with the

last dosage received within the past 10 years. Tetanus immune globulin (human) is required if tetanus immunization has not taken place or is inadequate

• Antimicrobial treatment should be administered for all bite wounds, with the exception of those patients who present 72 hours or more after injury with no clinical signs of infection. Antimicrobial therapy for bite wounds is not usually prophylactic, but rather a therapeutic intervention

• Antibiotics chosen for prophylaxis or treatment should be based on bacteriology. It is advisable to treat all patients having deep bite wounds with antibiotics, including puncture wounds, facial bites, and any wound over tendon or bone

Management• Obtaining cultures is helpful in guiding the therapy• Penicillin or ampicillin are the most active agents against P

multocida and the other oral flora; however, S aureus and about 50% of the anaerobic Gram-negative bacilli recovered in human bite wounds are resistant to this drug

• Isolation of beta-lactamase-producing organisms from more than 40% of bite wounds excludes the use of penicillin for bite

infections

Management• Although oxacillin is effective against S aureus, it has poor

activity against many bite isolates• Doxycycline is a good alternative; however, it should not be

used in young children• If S aureus is suspected (based on the Gram's stain of aspirate,

which is specific but not sensitive), penicillin (to cover streptococci) and penicillinase-resistant penicillin should be used

• Augmentin has been shown to be effective in treating human bites and dog bites and baring allergy is often 1st line

Management• Clindamycin and penicillinase-resistant penicillin should not be

administered without penicillin because of poorer activity against P multocida

• Erythromycin is generally ineffective against Fusobacterium, P multocida, Moraxella species, and peptostreptococci

• Azithromycin is generally more active than clarithromycin against all Pasteurella species– Azithromycin and clarithromycin are only modestly effective against E

corrodens and Peptostreptococcus species.• Cefoxitin or penicillin with a first-generation cephalosporin plus a beta-

lactamase-resistant penicillin or Unasyn will provide adequate parenteral therapy for animal or human bites

• The newer quinolones (eg, gatifloxacin, moxifloxacin) are active against all major bite wound pathogens, including anaerobic bacteria; however, these agents are not approved for use in children

Management• E corrodens, a capnophilic Gram-negative rod that is part of

normal oral flora, can be recovered from 25% of human bite wounds

• Susceptible to penicillin, ampicillin, and quinolones, E corrodens is resistant to clindamycin, methicillin, nafcillin, and oxacillin; certain strains are also resistant to cephalosporins

• Any isolated E corrodens, therefore, should have susceptibility testing if cephalosporin therapy is considered.

• Most bite wounds can be sutured with good results and an acceptable infection rate, with a 7- to 14-day course of abx for infections limited to soft tissue; a minimum of 21 days of therapy is generally required for infection involving joints or bones

Complications• Local wound infection with lymphangitis, local abscess, septic

arthritis, tenosynovitis, and osteomyelitis• Less common complications include endocarditis, meningitis,

brain abscess, and sepsis with DIC (disseminated intravascular coagulation)

• Individuals prone to complications include those receiving systemic corticosteroids and those suffering from lupus erythematosus and acute leukemia

• Hand wounds have a high rate of infection (30% or more) and complications are common with disastrous functional consequences

• Rabies must also be considered with dog bite wounds