Bites, Animal and Human

Basics

Dog bites more common than cat bites; ~90% cat bites are provoked
Human bites often clenched-fist injuries or incidental
Children with human bite marks with intercanine distance >3 cm: suspect adult bite and possible abuse

Bites cause tears, punctures, avulsions, crush injuries
Oral flora contamination leads to polymicrobial infections
Clenched-fist bites associated with alcohol/drugs and higher infection risk if presentation >8 hours

Details of incident: provoked/unprovoked, animal species, bite site, animal vaccine status
Patient comorbidities, immunization status (tetanus, rabies)

Common sites: dog bites—hands (adults), face (children); cat bites—hands, lower limbs, face; human bites—hands (MCP joints)
Infection signs: erythema, swelling, tenderness, purulent drainage, lymphangitis
Tenosynovitis signs in hand bites
Neurovascular status assessment

Wound culture (aerobic and anaerobic), Gram stain (85% positive cultures)
Blood cultures if bacteremia suspected
Imaging: X-ray or CT for foreign body, bone/joint injury, osteomyelitis suspicion
MRI for osteomyelitis, CT for severe skull bites
Ultrasound for abscess detection
Atypical pathogens culture if nonhealing wounds

Dog bites: Pasteurella spp. (~50%), Strep, Staph aureus, Capnocytophaga canimorsus, anaerobes
Cat bites: Pasteurella spp. (~75%), Strep pyogenes, MRSA, anaerobes
Human bites: Eikenella corrodens (15-29%), Strep, Staph (including MRSA), anaerobes
Aquatic bites: Vibrio spp., Aeromonas spp., Pseudomonas spp.
Rodent bites: Streptobacillus moniliformis (rat-bite fever)
Reptile bites: Pseudomonas, Salmonella, Clostridium
Asplenic and liver disease patients at high risk for severe C. canimorsus infection

Prophylaxis recommended for human bites and high-risk wounds (deep puncture, crush, venous/lymphatic compromise, hands, face/genital area, immunocompromised, asplenic, advanced liver disease, requiring surgery)
Duration: 3-5 days prophylaxis; 5-10 days for cellulitis/abscess
First line: Amoxicillin-clavulanate
Adults: 875/125 mg PO BID
Children: 45 mg/kg/day amoxicillin component divided BID, max 875 mg/dose
Severe infections/immunocompromised: Ampicillin-sulbactam or piperacillin-tazobactam IV
Second line: Clindamycin plus TMP-SMX or ciprofloxacin
Avoid 1st-gen cephalosporins, dicloxacillin, and clindamycin monotherapy due to lack of coverage for Pasteurella and Eikenella
Rabies immunoglobulin and vaccine if indicated
Tetanus toxoid or Tdap booster if >10 years since last dose
HIV PEP not routinely recommended unless significant exposure
Monkey bites: consider herpes B virus prophylaxis with antivirals (e.g., valacyclovir)

Debride devitalized tissue (avoid puncture wound debridement)
Primary closure considered for clean, <12-hour-old facial wounds
Leave infected or high-risk wounds open; delayed primary closure at 3-5 days possible