WORKUP	Section 5 of 10
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Lab Studies:

• Fresh wounds should not be cultured. Infected wounds are generally cultured.

• Other laboratory tests are indicated as the patient's condition dictates (eg, CBC and blood cultures for patients with sepsis).

• If C canimorsus sepsis is suspected, examine the peripheral smear for the organism, a bacillus.

Imaging Studies:

• Radiography is indicated if any concerns exist that deep structures are at risk (eg, hand wounds; deep punctures; crushing bites, especially over joints).

• Occult fractures or osteomyelitis may be discovered.

• Radiographs may find foreign bodies in the wound (eg, teeth).

• Children who have been bitten in the head should be examined for bony penetration with plain films or CT scan. If the child was shaken, consider cervical spine evaluation.

Other Tests:

• If patient has possible sepsis or other serious complications, further laboratory testing is needed. Otherwise, routine testing rarely is necessary.

	TREATMENT	Section 6 of 10
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Prehospital Care:

• Complete trauma evaluation occasionally may be indicated.

• Rinse wounds with sterile solution, if possible, and cover.

• Obtaining the history of the event is of major importance, including home treatment of wounds, body parts involved, and other symptoms (see History).

• Encourage patient to seek prompt care.

Emergency Department Care:

• Most wounds can be treated in the ED. Essentials of treatment are necessary inspection, debridement, irrigation, and closure, if indicated.

• Carefully inspect wounds to identify deep injury and devitalized tissue. It is nearly impossible to obtain an adequate inspection of a wound without it first being anesthetized. Care should be taken to visualize the bottom of the wound and, if applicable, to examine the wound through a range of motion.

• Debridement is an effective means of preventing infection. Removing devitalized tissue, particulate matter, and clots prevents these from becoming a source of infection, much like any foreign body. Clean surgical wound edges result in smaller scars and promote faster healing.

• Irrigation is another important means of infection prevention. A 19-gauge blunt needle and a 35-mL syringe provide adequate pressure (7 psi) and volume to clean most wounds. In general, 100-200 mL of irrigation solution per inch of wound is required. Heavily contaminated wounds require more irrigation. Large dirty wounds may require irrigation in the operating room. Isotonic sodium chloride solution is a safe, available, effective, and inexpensive irrigating solution. Few of the numerous other solutions and mixtures of saline and antibiotics have any advantages over saline. If a shieldlike device is used, take care to prevent the irrigating solution from returning to the wound, which decreases the effectiveness of the irrigation.

• Consider primary closure in relatively clean bite wounds or wounds that can be cleansed effectively. Others are best treated by delayed primary closure. Facial wounds, because of the excellent blood supply, are at low risk for infection, even if closed primarily. Bite wounds to the lower extremities, with a delay in presentation, or in immunocompromised hosts generally should be left open.

• Consider tetanus and rabies prophylaxis for all wounds.

• In one study of 145 recent (<6 h) dog bites of the face in 45 children, treatment with pressure irrigation and wound-edge excision resulted in a 0.4% infection rate without the use of antibiotics.

Consultations:

• Extensive wounds, those involving tissue loss, or those involving complex structures may require plastic surgery consultation.

• If the skull is penetrated, neurosurgery consultation is indicated.

	MEDICATION	Section 7 of 10
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This is one of most controversial subjects in wound care. Remember that proper wound care (inspection, debridement, irrigation, closure, if indicated) reduces infection more than antibiotics. In general, low-risk wounds, such as bite wounds to the face, do not need antibiotics. High-risk wounds (eg, cat bites that are a true puncture, bites to the hand, poor general health) generally require antibiotics. Literature does not support one clear recommendation.

Antirabies treatment may be indicated for bites by foxes, bats, raccoons, or skunks in the Americas (see Rabies for treatment and dosing information). For cat and dog bites, consult local public health authorities for their current recommendations if the offending animal cannot be secured and observed.

Drug Category: Antibiotics -- Proponents of oral antibiotics are in two camps: amoxicillin/clavulanate therapy versus amoxicillin and cephalexin therapy. Amoxicillin/clavulanate is assumed to cover staphylococci and Pasteurella species. A single medication taken 3 times a day should have good compliance. Two-drug therapy of amoxicillin and cephalexin seems to offer better coverage but may result in poorer compliance. Five days of prophylactic antibiotics generally is considered adequate.

Patients who are allergic to penicillin may use cefuroxime (cat), doxycycline (cat), erythromycin, or trimethoprim-sulfamethoxazole, although these are less effective. Clindamycin plus ciprofloxacin (adults) or clindamycin plus trimethoprim-sulfamethoxazole (pediatrics) may provide better coverage. Azithromycin may be an effective alternative because of high tissue concentration.

Drug Name	Amoxicillin and clavulanate (Augmentin) -- Drug combination that extends antibiotic spectrum of penicillin to include bacteria normally resistant to beta-lactam antibiotics. Indicated for skin and skin structure infections caused by beta-lactamase–producing strains of Staphylococcus aureus.
Adult Dose	500/125 mg PO tid or 875/125 mg PO bid
Pediatric Dose	10-15 mg/kg PO tid (based on amoxicillin component)
Contraindications	Documented hypersensitivity
Interactions	Coadministration with warfarin or heparin increases risk of bleeding
Pregnancy	B - Usually safe but benefits must outweigh the risks.
Precautions	Give for a minimum of 10 d to eliminate organism and prevent sequelae (endocarditis, rheumatic fever); following treatment, perform cultures to confirm eradication of streptococci

Drug Name	Amoxicillin (Trimox, Biomox, Amoxil) -- Alone, this drug is effective against Pasteurella species. However, not indicated for skin and skin structure infections caused by beta-lactamase–producing strains of Staphylococcus aureus. A second antibiotic such as cephalexin is needed for Staphylococcus infections.
Adult Dose	250-500 mg PO tid
Pediatric Dose	30-50 mg/kg/d PO divided tid; not to exceed 500 mg/dose
Contraindications	Documented hypersensitivity
Interactions	Reduces the efficacy of oral contraceptives
Pregnancy	B - Usually safe but benefits must outweigh the risks.
Precautions	Adjust dose in renal impairment; may enhance chance of candidiasis

Drug Name	Cephalexin (Keflex, Biocef, Keftab) -- First-generation cephalosporin that arrests bacterial growth by inhibiting bacterial cell wall synthesis. Bactericidal activity against rapidly growing organisms. Primary activity against skin flora.
Adult Dose	250-500 mg PO qid
Pediatric Dose	25-50 mg/kg/d PO divided qid; not to exceed 500 mg/dose
Contraindications	Documented hypersensitivity
Interactions	Coadministration with aminoglycosides increases nephrotoxic potential
Pregnancy	B - Usually safe but benefits must outweigh the risks.
Precautions	Adjust dose in severe renal insufficiency (high doses may cause CNS toxicity); superinfections and promotion of non-susceptible organisms may occur with prolonged use or repeated therapy

Drug Name	Erythromycin (Erythrocin, Eryc, E.E.S., Ery-Tab) -- Inhibits bacterial growth, possibly by blocking dissociation of peptidyl tRNA from ribosomes, causing RNA-dependent protein synthesis to arrest. For treatment of staphylococcal and streptococcal infections. In children, age, weight, and severity of infection determine proper dosage. When bid dosing is desired, half of total daily dose may be taken q12h. For more severe infections, double the dose
Adult Dose	250 mg PO qid
Pediatric Dose	20-50 mg/kg/d PO divided qid; not to exceed 500 mg/dose
Contraindications	Documented hypersensitivity; hepatic impairment
Interactions	Coadministration may increase toxicity of theophylline, digoxin, carbamazepine, and cyclosporine; may potentiate anticoagulant effects of warfarin; coadministration with lovastatin and simvastatin increases risk of rhabdomyolysis
Pregnancy	B - Usually safe but benefits must outweigh the risks.
Precautions	Caution in liver disease; estolate formulation may cause cholestatic jaundice; GI adverse effects are common (give doses pc); discontinue use if nausea, vomiting, malaise, abdominal colic, or fever occur

Drug Name	Sulfamethoxazole/trimethoprim (Bactrim, Bactrim DS, Septra, Septra DS) -- Inhibits bacterial growth by inhibiting synthesis of dihydrofolic acid.
Adult Dose	400-800 mg SMX PO bid
Pediatric Dose	30-60 mg/kg/d SMX PO divided bid; not to exceed 800 mg/dose
Contraindications	Documented hypersensitivity; megaloblastic anemia due to folate deficiency
Interactions	May increase PT when used with warfarin (perform coagulation tests and adjust dose accordingly); coadministration with dapsone may increase blood levels of both drugs; coadministration of diuretics increases incidence of thrombocytopenia purpura in elderly; phenytoin levels may increase with coadministration; may potentiate effects of methotrexate in bone marrow depression; hypoglycemic response to sulfonylureas may increase with coadministration; may increase levels of zidovudine
Pregnancy	C - Safety for use during pregnancy has not been established.
Precautions	Discontinue at first appearance of skin rash or sign of adverse reaction; obtain CBCs frequently; discontinue therapy if significant hematologic changes occur; goiter, diuresis, and hypoglycemia may occur with sulfonamides; prolonged IV infusions or high doses may cause bone marrow depression (if signs occur, give 5-15 mg/d leucovorin); caution in folate deficiency (eg, chronic alcoholism, advanced age, anticonvulsant therapy, malabsorption syndrome); hemolysis may occur in G-6-PD deficiency; patients with AIDS may not tolerate or respond to TMP-SMZ; caution in renal or hepatic impairment (perform urinalyses and renal function tests during therapy); give fluids to prevent crystalluria and stone formation

Drug Name	Clindamycin (Cleocin) -- Lincosamide for treatment of serious skin and soft tissue staphylococcal infections. Also effective against aerobic and anaerobic streptococci (except enterococci). Inhibits bacterial growth, possibly by blocking dissociation of peptidyl tRNA from ribosomes, causing RNA-dependent protein synthesis to arrest.
Adult Dose	300 mg PO qid
Pediatric Dose	10-25 mg/kg/d PO divided qid; not to exceed 600 mg/dose
Contraindications	Documented hypersensitivity; regional enteritis, ulcerative colitis, hepatic impairment, antibiotic-associated colitis
Interactions	Increases duration of neuromuscular blockade induced by tubocurarine and pancuronium; erythromycin may antagonize effects of clindamycin; antidiarrheals may delay absorption of clindamycin
Pregnancy	B - Usually safe but benefits must outweigh the risks.
Precautions	Adjust dose in severe hepatic dysfunction; no adjustment necessary in renal insufficiency; associated with severe and possibly fatal colitis by allowing overgrowth of Clostridium difficile

Drug Name	Ciprofloxacin (Cipro) -- Fluoroquinolone with activity against pseudomonads, streptococci, MRSA, S epidermidis, and most gram-negative organisms, but no activity against anaerobes. Inhibits bacterial DNA synthesis and, consequently, growth. Trovafloxacin (Trovan) overcomes many of these limitations. Continue treatment for at least 2 d (7-14 d typical) after signs and symptoms have disappeared.
Adult Dose	500 mg PO bid
Pediatric Dose	Not recommended
Contraindications	Documented hypersensitivity
Interactions	Antacids, iron salts, and zinc salts may reduce serum levels; administer antacids 2-4 h before or after taking fluoroquinolones; cimetidine may interfere with metabolism of fluoroquinolones; ciprofloxacin reduces therapeutic effects of phenytoin; probenecid may increase ciprofloxacin serum concentrations; may increase toxicity of theophylline, caffeine, cyclosporine, and digoxin (monitor digoxin levels); may increase effects of anticoagulants (monitor PT)
Pregnancy	C - Safety for use during pregnancy has not been established.
Precautions	In prolonged therapy, perform periodic evaluations of organ system functions (eg, renal, hepatic, hematopoietic); adjust dose in renal function impairment; superinfections may occur with prolonged or repeated antibiotic therapy

Drug Name	Azithromycin (Zithromax) -- Inhibits bacterial growth, possibly by blocking dissociation of peptidyl tRNA from ribosomes, causing RNA-dependent protein synthesis to arrest. Treats mild-to-moderate microbial infections
Adult Dose	500 mg PO d 1, then 250 mg PO qd for 4 d
Pediatric Dose	10 mg/kg PO d 1; not to exceed 500 mg/dose, then 5 mg/kg PO qd for 4 d; not to exceed 250 mg/dose
Contraindications	Documented hypersensitivity; hepatic impairment; do not administer with pimozide
Interactions	May increase toxicity of theophylline, warfarin, and digoxin; effects are reduced with coadministration of aluminum and/or magnesium antacids; nephrotoxicity and neurotoxicity may occur when coadministered with cyclosporine
Pregnancy	B - Usually safe but benefits must outweigh the risks.
Precautions	Site reactions can occur with IV route; bacterial or fungal overgrowth may result from prolonged antibiotic use; may increase hepatic enzymes and cholestatic jaundice; caution in patients with impaired hepatic function, prolonged QT intervals, or pneumonia; caution in hospitalized, geriatric, or debilitated patients

Drug Name	Doxycycline (Doryx, Vibramycin, Bio-Tab) -- Inhibits protein synthesis and thus bacterial growth by binding to 30S and possibly 50S ribosomal subunits of susceptible bacteria.
Adult Dose	100 mg PO bid
Pediatric Dose	<8 years: Not recommended >8 years: 2-5 mg/kg/d PO in 1-2 divided doses; not to exceed 200 mg/d
Contraindications	Documented hypersensitivity; severe hepatic dysfunction
Interactions	Bioavailability decreases with antacids containing aluminum, calcium, magnesium, iron, or bismuth subsalicylate; tetracyclines can increase hypoprothrombinemic effects of anticoagulants; tetracyclines can decrease effects of oral contraceptives, causing breakthrough bleeding and increased risk of pregnancy
Pregnancy	D - Unsafe in pregnancy
Precautions	Photosensitivity may occur with prolonged exposure to sunlight or tanning equipment; reduce dose in renal impairment; consider drug serum level determinations in prolonged therapy; tetracycline use during tooth development (last one half of pregnancy through age 8 y) can cause permanent discoloration of teeth; Fanconilike syndrome may occur with outdated tetracyclines

Drug Name	Cefuroxime (Ceftin, Kefurox, Zinacef) -- Second-generation cephalosporin maintains gram-positive activity that first-generation cephalosporins have; adds activity against P mirabilis, H influenzae, E coli, K pneumoniae, and M catarrhalis. Condition of patient, severity of infection, and susceptibility of microorganism determine proper dose and route of administration.
Adult Dose	500 mg PO bid
Pediatric Dose	15-30 mg/kg/d PO divided bid; not to exceed 500 mg/dose
Contraindications	Documented hypersensitivity
Interactions	Disulfiramlike reactions may occur when alcohol is consumed within 72 h after taking cefuroxime; may increase hypoprothrombinemic effects of anticoagulants; may increase nephrotoxicity in patients receiving potent diuretics such as loop diuretics; coadministration with aminoglycosides increases nephrotoxic potential
Pregnancy	C - Safety for use during pregnancy has not been established.
Precautions	Reduce dosage by half if creatinine clearance is 10-30 mL/min, and by 3/4 if <10 mL/min (high doses may cause CNS toxicity); bacterial or fungal overgrowth of nonsusceptible organisms may occur with prolonged or repeated therapy

	FOLLOW-UP	Section 8 of 10
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Further Inpatient Care:

• Patients with infected animal bites may need inpatient care. This depends on the general health of the patient, the extent and nature of the infection, and the patient's compliance.

• Consider admitting patients with hand bites that become infected (generally involving deep structures).

Further Outpatient Care:

• Close follow-up care is essential in animal bite wounds. Reevaluate any significant bite for signs of infection in 24 (for cat bites) to 48 hours.

In/Out Patient Meds:

• Outpatient intravenous antibiotics may be possible for some patients.

• Intravenous antibiotics for cat bites: Consider penicillin G for Pasteurella multocida plus a staphylococcal coverage antibiotic (eg, cefazolin or trimethoprim/sulfamethoxazole [TMP/SMX]). Do not use cephalosporins alone. For patients allergic to penicillin, some authors recommend azithromycin and staphylococcal coverage.

• Intravenous antibiotics for dog bites: Consider ampicillin/sulbactam. For patients allergic to penicillin, consider clindamycin and ciprofloxacin (adult) and clindamycin and TMP/SMX (children).

Transfer:

• Patients who require extensive repair or prolonged inpatient care may need transfer to a tertiary care facility.

Complications:

• Wound infection

• Sepsis

• Cosmetic deformity

• Loss of limb

Prognosis:

• The prognosis is generally excellent.

Patient Education:

• Educating patients about the risk of infection despite proper wound care, antibiotics (if indicated), and close follow-up care is very important. Even wounds that have received the best care may become infected. Teach patients the signs of infection and the need for prompt attention if the wound should become infected.

• For excellent patient education resources, visit eMedicine's Bites and Stings Center and Bacterial and Viral Infections Center. Also, see eMedicine's patient education articles Animal Bites and Rabies.

	MISCELLANEOUS	Section 9 of 10
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Medical/Legal Pitfalls:

• Meticulous documentation of both the history of the bite and of treatment is important to prevent questions about the appropriateness of care. Documentation should include decisions about antibiotic use and other aspects of care.

• In many locations, animal bites must be reported to local authorities.

Special Concerns:

• Pediatric patients

• Previously bitten patients remain at risk if the dog, cat, or other animal that bit them continues to be aggressive or is located where another bite could occur.

• Move the animal to another location.

	BIBLIOGRAPHY	Section 10 of 10
Author Information Introduction Clinical Differentials Workup Treatment Medication Follow-up Miscellaneous Bibliography

• Callaham M: Bites and Injuries Inflicted by Mammals In: Auerbach PS, ed. Wilderness Medicine. 3rd ed. St Louis: Mosby-Year Book; 1995:927-93.
• CDC: Nonfatal dog bite-related injuries treated in hospital emergency departments--United States, 2001. MMWR Morb Mortal Wkly Rep 2003 Jul 4; 52(26): 605-10[Medline].
• Cummings P: Antibiotics to prevent infection in patients with dog bite wounds: a meta-analysis of randomized trials. Ann Emerg Med 1994 Mar; 23(3): 535-40[Medline].
• Dire DJ: Cat bite wounds: risk factors for infection. Ann Emerg Med 1991 Sep; 20(9): 973-9[Medline].
• Gilbert DN, Moellering RC, Sande MA: Bites. In: The Sanford Guide to Antimicrobial Therapy. 29th ed. Dallas, Tx: Antimicrobial Therapy, Inc; 1999:36.
• Guy RJ, Zook EG: Successful treatment of acute head and neck dog bite wounds without antibiotics. Ann Plast Surg 1986 Jul; 17(1): 45-8[Medline].
• Talan DA, Citron DM, Abrahamian FM, et al: Bacteriologic analysis of infected dog and cat bites. N Engl J Med 1999 Jan 14; 340(2): 85-92[Medline].
• Trott A: Bite wounds. In: Wounds and lacerations emergency care and closure. 2nd ed. St Louis, Mo: Mosby-Year Book, Inc; 1997:265-84.
• Weber EJ, Callaham M: Animal bites and rabies. In: Rosen P, Barkin R, eds. Emergency Medicine: Concepts and Clinical Practice. Vol 1. St Louis, Mo: Mosby-Year Book; 1998:906-21.

Bites, Animal excerpt