summary Dog and Cat Bites to the hand are common and are associated with secondary infections due to a large number of animal oral flora pathogens. Diagnosis is often delayed and is confirmed with a careful history and physical examination. Treatment is generally oral antibiotics but presence of soft tissue infection, abscess or tenosynovitis requires urgent irrigation and debridement. Epidemiology Incidence (dog > cat > human) dog bites are most common animal bites in the US (90%) dog is known to victim in 90% of cases cat bites are 2nd most common (10%) human bites are 3rd most common Demographics more common in males more frequent at ages 2-19 years Anatomic Location upper extremity > lower extremity Etiology Pathophysiology mechanism dog bites cause crush, puncture, avulsion, tears and abrasions large dogs' jaws exert >450lbs/ square inch more likely to cause structural damage to nerves, vessels, joints cat bites penetrate bones and joints, and cause septic arthritis and osteomyelitis small, sharp teeth cause puncture wounds that seal immediately penetrate joints and flexor tendons higher risk for infection than dog bites microbiology most infections are polymicrobial, with > 1 anerobe most common isolate from both cats and dogs is Pasteurella sp. gram-negative, facultative, anaerobic, pleomorphic coccobacillus inform lab about potential for Pasteurella cultures require appropriate growth media and take 1wk to grow dog bites Pasteurella (50% of dog bite infections) Pasteurella canis Staphylococcus aureus Streptococcus alpha-hemolytic Corynebacterium anerobes (e.g. Bacteroides) Capnocytophaga canimorsus rare, potentially fatal (in splenectomy patients) causes cellulitis, sepsis, endocarditis, meningitis, DIC, ARDS and death highest mortality in immunocompromised (30-60%) cat bites Pasteurella (most common, 70-80% of cat bite infections) Pasteurella multocida and Pasteurella septica causes intense pain, swelling in 48h other organisms similar to dog bites Associated conditions secondary bacterial infection most bites do not become infected risk factors for infection bite to hand, foot, or major joint puncture wounds or crush injuries treatment delay >12h age >50y preexisting host disease immune suppression (steroids, asplenism) chronic alcoholism diabetes mellitus vascular disease existing edema of extremity rabies caused by a rhabdovirus common animal carriers include dogs, raccoons, bats, foxes increased risk with open wounds, scratches/abrasions, mucous membranes Presentation History important to determine type of animal time since injury presence of comorbidities Symptoms pain and swelling bleeding signs of local or systemic sepsis Physical Exam evaluate depth of puncture wound and presence of crush injury check for neurovascular status look for joint penetration important to photograph wounds Imaging Radiographs indications to obtain crush injuries suspected fracture suspected foreign body Studies Culture indications if signs of infection are present routine culture not indicated technique deep aerobic and anaerobic culture Diagnosis Clinical diagnosis is made with careful history and physical examination Treatment Nonperative copious irrigation, prophylactic antibiotics, tetanus toxoid, +/- rabies prophylaxis copious irrigation in emergency room saline (>150ml) irrigation with 18-19G needle or plastic catheter use povidone-iodine solution if high risk of rabies indications for antibiotics cat bites presentation >8h immune compromised or diabetic hand bite deep bites choice of antibiotics amoxicillin/clavulanic acid effective against Pasteurella multocida cefuroxime ceftriaxone rabies prophylaxis indicated when any suspicion for rapid animal suspect if unprovoked attack by animal with bizarre behavior human diploid cell vaccine and human rabies immunoglobulin immobilization immobilize and elevate extremity Operative formal surgical debridement indications crush or devitalized tissue foreign body bites to digital pulp space, nail bed, flexor tendon sheath, deep spaces of the palm, joint spaces tenosynovitis septic arthritis abscess formation Prognosis Serious and fatal bites include large, aggressive dogs small children head and neck bites