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Wednesday, August 19, 2009

Bite, Animal

Bite, Animal
• Most bites are from provoked animals
• Dog bite wounds:
o Large dogs inflict the most serious wounds (pit bulls cause the most human fatalities).
o Most fatalities in children (70%) due to bites to face/neck
o Dogs of family or friends account for most bites.
• Cat bite wounds:
o Majority from pets known to victim
o 50% infection rate in those seeking care
o Puncture wounds most frequent due to sharp thin teeth causing deep inoculation of bacteria
• Cat-scratch disease:
o Three of the following four criteria:
Cat contact, with presence of scratch or inoculation lesion of the skin, eye, or mucous membrane
Positive CSD skin test result
Characteristic lymph node histopathology
Negative results of laboratory studies for other causes of lymphadenopathy
• Rat bite wounds:
o Occur in laboratory personnel or children of low socioeconomic class
o Infection rate
o Rat bites rarely transmit rabies, and prophylaxis not routine
• Dog and cat bites:
o Pasteurella multocida is the major organism in both
Twice as likely to be found in cat bites than dog bites
Gram-negative aerobe found in up to 80% of cat infections
Infection appears in <24 hours
o Staphylococcus or Streptococcus
Infection appears in >24 hours
o Other organisms include anaerobes and Capnocytophaga canimorsus (dogs)
• Cat-scratch disease:
o Caused by Bartonella henselae
• Rat bites:
o Caused by Spirillum minus and Streptobacillus moniliformis
Signs and Symptoms
• Distribution of mammalian bites:
o Dog bites represent 80-90% of all bites.
o Cat bites represent 5-15% of all bites.
o Human bites represent 2-5% of all bites (see Human Bite chapter).
o Rat bites represent 2-3% of all bites.
• Dog bites:
o Appearance
Crush injuries (most common), tears, avulsions, punctures, and scratches
o Low rates of infection compared with cat and human bites
o Infections usually present with:
Malodorous gray discharge
• Cat bites:
o Appearance
Puncture wounds (most common)
o High infection rates (30-50%) due to deeper puncture wounds
• Cat-scratch disease:
o From the bite/scratch of a cat, dog, or monkey
o Small macule or vesicle that progresses to a papule
Begins several days (3-10) after inoculation
Resolves within several days or weeks
Regional lymphadenopathy occurs 3 weeks postinoculation
Resolves after 2-4 months
o Low-grade fever, malaise, headache
• Animal's behavior, provocation, location, ownership
• Time since attack
• Past medical history: conditions compromising immune function, allergies, and tetanus status
Physical Exam
• Record the location and extent of all injuries.
• Document any swelling, crush injuries, or devitalized tissue.
• Note the range of motion of affected areas.
• Note the status of tendon and nerve function.
• Document any signs of infection, including regional adenopathy.
• Document any joint or bone involvement.
• Aerobic and anaerobic cultures from any infected bite wound
• Cultures not routinely indicated if wounds not clinically infected
• Cat-scratch disease
o Presence of elevated titers of Bartonella (Rochalimaea) henselae, or
o Positive reaction to cat-scratch antigen (CSA)
Inject 0.1 mL CSA intradermally
Induration at the site 48-72 hours later equal to or exceeding 5 mm is positive
Plain radiograph indications:
• Fracture
• Suspect foreign body, e.g., tooth
• Baseline film if a bone or joint space has been violated in evaluating for osteomyelitis
• For infection in proximity to a bone or joint space
Differential Diagnosis
• Human bite injuries: human teeth cause crush injuries and animal teeth cause more punctures and lacerations.
• Bite injuries from other animals
• CSD-caused lymphadenopathy:
o Reactive hyperplasia (leading cause of lymphadenopathy in children younger than 16 years)
o Infection, chronic lymphadenitis, drug reaction, malignancy, and congenital conditions

Initial Stabilization
• Achieve hemostasis on any bleeding wound.
• Airway stabilization if bite located on face or neck
ED Treatment
• Wound irrigation:
o Copious volumes of normal saline irrigation with an 18-gauge plastic catheter tip aimed in the direction of the puncture
o Avoid injection of saline through tissue planes due to force of irrigation
• Debridement:
o Remove foreign material, necrotic skin tags, or devitalized tissues
o Do not debride puncture wounds
o Remove any eschar present so underlying pus may be expressed and irrigated
• Wound closure:
o Closing wounds increases risk of infection and must be balanced with scar formation and effect of leaving wound open to heal secondarily.
o Do not suture infected wounds or wounds >24 hours after injury.
o Repair of wounds >8 hours: controversial
o Close facial wounds (warn patient of high risk of infection).
o Infected wounds, those presenting >24 hours after the event, and deep hand wounds should be left open
o May approximate the wound edges with Steri-Strips and perform a delayed primary closure
• Antibiotic indications:
o Infected wounds
o Cat bites
o Hand injuries
o Severe wounds with crush injury
o Puncture wounds
o Full-thickness puncture of hand, face, or lower extremity
o Wounds requiring surgical debridement
o Wounds involving joints, tendons, ligaments, or fractures
o Immunocompromised patients
o Wounds presenting >8 hours after the event
• Elevate injured extremity.
• Tetanus prophylaxis
Rabies Immunoprophylaxis
• Not required if rabies not known or suspected
• Rodents (squirrels, hamsters, rats, mice) and rabbits rarely transmit the disease.
• Skunks, raccoons, bats, and foxes represent the major reservoir for rabies.
• Recommended in following situations:
o Dog or cat in rabies-known area unable to be quarantined for 10 days
o Previously healthy dog or cat becomes ill while being quarantined (and awaiting results of rabies fluorescent antibody test)
o An ill dog or cat while awaiting rabies test results (to be continued or halted based on results of rabies test)
• Active immunization:
o Human diploid cell vaccine (HDCV): 1 mL IM on days 1, 3, 7, 14, and 28 after exposure
• Passive immunization:
o Human rabies immune globulin (HRIG): 20 IU/kg
o Up to one half in area around wound with the rest IM
Cat-Scratch Disease
• Analgesics
• Apply local heat to affected nodes.
• Avoid lymph node trauma.
• Disease usually self-limiting
• Antibiotics controversial, consider if severe disease is present or immunocompromised victim
Medication (Drugs)
• Amoxicillin/clavulanic acid (Augmentin): 500-875 mg (peds: 40 mg/kg/24 hr) PO b.i.d. (first line for all three animals)
• Ampicillin/sulbactam (Unasyn): 1.5-3.0 g IV q6h
• Cefoxitin (Mefoxin): 2.0 g IV q8h
• Cefuroxime axetil (Ceftin): 500 mg PO b.i.d.
• Clindamycin (Cleocin): 300 mg PO q6h; 900 mg IV q8h
• Ciprofloxacin (Cipro): 500 mg PO b.i.d.; 400 mg IV q12h
• Doxycycline (Vibramycin): 100 mg PO b.i.d.
• Imipenem/cilastatin (Primaxin): 0.5-1.0 g (peds: 50 mg/kg/24h) IV q6h
• Piperacillin/tazobactam (Zosyn): 3.375 g IV q6h
• Ticarcillin/clavulanic acid (Timentin): 3.1 g IV q6h
• Trimethoprim-sulfamethoxazole (Bactrim): 1 tablet (peds: 6-12 mg TMP, 30-60 mg SMX/kg/24h) PO b.i.d.
Admission Criteria
• All bites:
o Infected wounds at presentation
o Severe/advancing cellulitis/lymphangitis
o Signs of systemic infection
o Infected wounds that have failed to respond to outpatient (PO) antibiotics
• Cat-scratch disease:
o Prolonged fever, systemic symptoms, and/or marked lymphadenopathy
Discharge Criteria
• Healthy patient with localized wound infection: discharge on antibiotics with 24-hour follow-up.
• 48-hour follow-up for noninfected wounds
1. Brook I. Microbiology and management of human and animal bite wound infections. Prim Care. 2003;30(1):25-39, v.
2. Galloway RE. Mammalian bites. J Emerg Med. 1998;6:325-331.
3. Griego RD, et al. Dog, cat, and human bites: a review. J Am Acad Dermatol. 1995;33: 1019-1029.
4. Klein JD. Cat scratch disease. Pediatr Rev 1994; 15(9):348-353.
5. Pickering L, Red Book: 2003 Report of the Committee on Infectious Diseases. Amer Academy of Pediatrics 2003. 26th edition.
6. Smith PF, et al. Treating mammalian bite wounds. J Clin Pharm Ther. 2000;25:85-99.

See also: Rabies

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