Management of cat and dog bites

Management of cat and dog bites – includes patient information sheet

Katherine T. Lewis

Each year approximately 1 to 2 million Americans are bitten by cats and dogs.(1) Because most bites are not reported and do not require medical attention, a more accurate estimate cannot be provided. In the United States, persons with cat and dog bites account for 1 percent of all emergency department visits and over 10,000 hospitalizations annually.(1) Ten to 20 dog bite–related fatalities occur each year in this country; 70 percent of these victims are children under 10 years of age.(2)(3) Young men are bitten more frequently by dogs; young women usually sustain cat bites.

Cat and dog bites most frequently involve the upper extremities. Dog bites on the head and neck are usually seen in young children. Large dogs can exert a pressure greater than 450 psi, which is enough to penetrate light sheet metal. Since dogs have large teeth designed specifically for tearing tissue, bites usually result in lacerations, avulsions, puncture wounds or crush injuries (Figure 1). Because of the extremely fine, sharp teeth of cats, bites usually present as deep puncture wounds. Approximately 30 to 40 percent of cat bite wounds become infected; the incidence of infection in persons with dog bite wounds is 15 to 20 percent.(1)

[ILLUSTRATION OMITTED]

History

A through history is essential in the assessment and management of the patient with a bite wound. Information that is useful in determining the patient’s risk of wound infection and rabies includes the general health and immunization status of the animal, whether the animal was provoked, and the time of the injury. The patient’s tetanus immunization status, current medications and allergies should be noted. Since bites may result in severe crush injuries and deep puncture wounds, as well as lacerations and skin avulsions, muscular and neurovascular compromise should always be ruled out. Finally, any history of chronic illness, immunocompromising conditions, immunosuppressive therapy, or presence of a prosthetic valve or joint should be noted.

Physical Examination

Physical examination includes measurement and classification of the wound (laceration, puncture, crush injury or avulsion) and a thorough neurovascular examination. Wound depth, as well as any tendon, ligament, bone or joint involvement should be determined. Puncture wounds usually appear shallow but are often quite deep and have devastating functional sequelae if not properly treated. Exploration of more serious wounds, especially those on the palmar side of the hand, should be done by a surgeon who specializes in hand injuries. In the case of facial and/or scalp wounds, the possibility that the central nervous system has been penetrated should be considered.

Photodocumentation is useful in cases of disfigurement or in cases that may involve litigation, such as a wound inflicted by an unleashed dog.

Microbiology

Much is known about the microbiology of bite wounds, including new information regarding some clinically important organisms.(1)(2)(4)(5) Several studies have shown both clinically infected and noninfected bite wounds to be polymicrobial; a mean of 2.8 to 3.6 bacterial species per wound are found in dog and cat bite wounds(2)(4) (Table 1). When cultured, more than 80 percent of dog bite wounds yield potential pathogens, yet only 15 to 20 percent of these wounds become clinically infected.(1) Predicting which wounds constitute the 15 to 20 percent that will become clinically infected continues to be a subject of considerable study.

TABLE 1 Microorganisms Isolated from Clinically Infected Dog and Cat Bite

Wounds

Aerobes

Afipia felis Neisseria species

Capnocytophaga canimorsus Pasteurella multocida

(DF-2) Pseudomonas species

Eikenella corrodens Staphylococcus aureus

Enterobacter species Staphylococcus epidermidis

Flavobacterium species Staphylococcus intermedius

Haemophilus aphrophilus Streptococci: alpha-hemolytic,

II-J, II-R beta-hemolytic, gamma-

Moraxella species hemolytic

Anaerobes

Actinomyces

Bacteroides species

Eubacterium species

Fusobacterium species

Leptotrichia buccalis

Viellonella parvula

Unusual pathogens

Blastomyces dermatitidis

Francisella tularensis

Derived from references 4, 5 and 6.

PASTEURELLA MULTOCIDA

Pasteurella multocida, a gram-negative aerobe present in the oropharynx of the majority of healthy dogs and cats, is found in 20 to 30 percent of dog bite wounds and more than 50 percent of cat bite wounds. Cellulitis is the most common manifestation of P. multocida infection in humans. Typically, P. multocida causes a rapidly developing (less than 24 hours) intense inflammatory reaction, occasionally associated with purulent discharge and fever.(6) Osteomyelitis, septic arthritis, respiratory infection, peritonitis, meningitis and sepsis have also been described.(7) Chronic liver disease is often associated with P. multocida sepsis, which presumably results from impairment of the reticuloendothelial system.(8) Despite the characteristic rapidly developing clinical infection, cultures may take up to one week to grow. Recently, a more virulent strain of the organism, called P. multocida dagmatis, has been described.(9)

CAPNOCYTOPHAGA CANIMORSUS

Capnocytophaga canimorsus (formerly known as DF-2) is a fastidious gram-negative bacillus that has been implicated in about 52 additional cases since the first case was reported in 1976.(10) While serious infection caused by C. canimorsus is rare, it is associated with a 28 percent fatality rate.(11) It has been noted that 80 percent of patients with serious infection are immunocompromised.(11) The diagnosis of infection with C. canimorsus is often difficult because cultures usually take three to 14 days to grow. Treatment includes supportive care and antibiotics (Table 2). C. canimorsus is usually sensitive to penicillin, amoxicillin-clavulanate, cefoxitin (Mefoxin), erythromycin, tetracycline and clindamycin (Cleocin).

TABLE 2 Antimicrobial Susceptibilities of Bacteria Frequently Isolated

from Animal Bite Wounds(*)

Staphylococcus Eikenella

Antimicrobial agent aureus corrodens

Penicillin Low High

Dicloxacillin (Pathocil) High Low

Amoxicillin-clavulanate

(Augmentin) High High

Cephalexin (Keflex) High Low

Cefuroxime (Zinacef) High Medium

Cefoxitin (Mefoxin) High High

Erythromycin High Low

Tetracycline High High

Trimethoprim-

sulfamethoxazole

(Bactrim, Septra, Trimpex) High High

Quinolones High High

Clindamycin (Cleocin) High Low

Pasteurella

Antimicrobial agent Anaerobes multocida

Penicillin Medium/high([dagger]) High

Dicloxacillin (Pathocil) Medium Low

Amoxicillin-clavulanate

(Augmentin) High High

Cephalexin (Keflex) Medium Low

Cefuroxime (Zinacef) Medium High

Cefoxitin (Mefoxin) High High

Erythromycin Medium Low

Tetracycline Medium High

Trimethoprim-

sulfamethoxazole

(Bactrim, Septra, Trimpex) Low High

Quinolones Medium High

Clindamycin (Cleocin) High Low

Capnocytophaga Staphylococcus

Antimicrobial agent canimorsus intermedius

Penicillin High Medium

Dicloxacillin (Pathocil) NS High

Amoxicillin-clavulanate

(Augmentin) High High

Cephalexin (Keflex) NS High

Cefuroxime (Zinacef) NS NS

Cefoxitin (Mefoxin) High NS

Erythromycin High High

Tetracycline High NS

Trimethoprim-

sulfamethoxazole

(Bactrim, Septra, Trimpex) Variable NS

Quinolones NS NS

Clindamycin (Cleocin) High High

NS = not studied.

(*)–Data are compiled from various studies.

([dagger])–Susceptibility of human-bite isolates/susceptibility of animal-bite isolates.

Adapted from Goldstein EJ. Bite wounds and infection. Clin Infect Dis 1992; 14:633-48. Used with permission.

CAT-SCRATCH DISEASE

Cat-scratch disease, caused by the gramnegative rod Afipia felis, can result from a scratch or bite from a dog, cat or monkey. Infection is characterized by an erythematous papule at the primary site of infection and the development of adenitis with fever several days after the scratch. Infection caused by A. felis usually regresses spontaneously within two months. In severe cases, a trial of tetracycline may be prescribed.(12)

Laboratory and Radiologic Studies

Laboratory and radiologic studies are performed in special circumstances. Gram stain is not useful in predicting the risk of infection in clinically noninfected wounds, and it is not routinely used in the evaluation of bite wounds. Both aerobic and anaerobic cultures are recommended in wounds that are clinically infected. The laboratory should be instructed to hold cultures for a minimum of seven to 10 days since pathogens may be slow-growing. If significant blood loss is suspected, hemoglobin or hematocrit should be obtained. Liver function and coagulation studies are useful in patients with sepsis. Radiographs should be obtained if bone penetration, fracture or foreign body are suspected.

Management

WOUND CARE

Wound care begins with cleansing using a 1 percent povidine iodine solution (Betadine). Because it can be toxic to tissue, povidine iodine surgical scrub should not be used. Irrigation with either normal saline or Ringer’s lactate solution may reduce the rate of infection by up to 20-fold, and it is an essential step in the proper management of bite wounds.(13) Irrigation is usually done with an 18- or 20-gauge needle or angiocath, a 20- to 50-mL syringe, and a minimum of 150 mL of irrigation solution. Debridement should be considered if devitalized, crushed tissue is present. As in all wound care, universal precautions should be taken.

The approach to closure of bite wounds remains extremely controversial. Clinically infected wounds, wounds over 24 hours old and puncture wounds should be left open. Most hand bite wounds should not be closed primarily. If closure is necessary, the wound edges should be loosely approximated so as not to interfere with drainage. Delayed primary closure may be done three to five days after the bite if no sign of infection is present. Bite wounds of the head, neck, arms and legs are generally closed primarily, and carry little risk of infection, if cleaned properly before closure.

All bite wounds, especially wounds involving the hand, wounds involving crushed bone and tissue, and wounds that are large or clinically infected, should be elevated. A three to five-day period of immobilization using a plaster splint in the position of function is often useful in the treatment of infected hand wounds.(1)

ANTIMICROBIAL THERAPY

While the microbiology of bite wounds has been examined extensively, further study is necessary to settle controversies in antibiotic therapy and wound management, and to more accurately predict clinical outcome. Recent studies of bite wound microbiology, treatment and clinical outcome have been of limited value because of small sample size and variations in type and site of injury, time from injury to treatment and type of treatment given. The choice of antibiotic therapy in bite wounds remains extremely controversial.(14)(15) The use of prophylactic antibiotics when no obvious sign of clinical infection is present is suggested for wounds that have a high risk of infection (Table 3). Wound characteristics, host factors and anticipated degree of compliance should be considered in all treatment decisions.(16) The duration of prophylactic antibiotic treatment ranges from three to seven days.(1)(2)

TABLE 3 High-Risk Bite Wounds

Full-thickness puncture wounds

Severe crush injury and/or edema

Wounds that require surgical debridement

Cat bite wounds

Bite wounds to the hand, foot or face

Bone, joint, tendon or ligament involvement

Wound adjacent to a prosthetic joint

Underlying diseases: diabetes mellitus, chronic

liver or pulmonary disease, history of

splenectomy, malignancy, acquired

immunodeficiency syndrome and other

immunocompromising conditions

A list of suggested antibiotics and dosages for the treatment of bite wounds is given in Table 4. In general, the chosen antibiotic should cover the oral flora of the animal, the skin flora of the victim and any likely environmental contaminants. While amoxicillin-clavulanate is the drug of choice for outpatient treatment of dog and cat bite wounds,(17)(18) penicillin can be used for minor wounds; it has a lower cost and a more favorable side effect profile. P. multocida and most anaerobes found in bite wounds are sensitive to penicillin (Table 2).

TABLE 4 Empiric Antibiotic Treatment of Cat and Dog Bite Wounds

Antibiotic Dosage

Outpatient

Antibiotic of choice

Amoxicillin-clavulanate Adults: 500 mg three times per

day

(Augmentin) Children: 40 mg amoxicillin per

kg per day,

in divided doses every eight

hours

Alternatives

Penicillin V Adults: 500 mg four times per

day

Children: 50 mg per kg per day,

in divided

doses every six to eight hours

Doxycycline(*) (Vibramycin, Adults: 100 mg two times per

day

Doryx, Vibra-tabs, etc.) Children: 2 to 4 mg per kg per

day, in

divided doses every 12 hours

Ceftriaxone([dagger]) (Rocephin) Adults: 1 g every 24 hours

intramuscularly

or intravenously

Children: 50 mg per kg per day

once a day

Inpatient

Antibiotic of choice

Cefoxitin (Mefoxin) Adults: 1 to 2 g every four to

eight hours

Children: 25 to 50 mg per kg

per day, in

divided doses every six hours

Alternatives

Ampicillin-sulbactam Adults: 1.5 to 3.0 g every six

hours

(Unasyn)([double dagger])

Ticarcillin-clavulanate Adults: 3.1 g every six hours

(Timentin)([double dagger])

Ceftriaxone Adults: 1 to 2 g every 24 hours

Children: 50 to 100 mg per kg

per day, in

divided doses every 24 hours

(*)–Do not use in pregnant women or in children under eight years of age.

([dagger])–One to two doses may be sufficient for prophylaxis in certain cases.

([double dagger])–Safety and efficacy have not been established in infants and children under the age of 12 years.

Doxycycline (Vibramycin, Doryx, Vibratabs, etc.) is suggested for patients who are allergic to penicillin, except children and pregnant women.(4) Since P. multocida is generally resistant to the first-generation oral cephalosporins, erythromycin, clindamycin (Cleocin) and penicillinase-resistant penicillins, these antibiotics are not recommended.(1)(4)(8)(9) Erythromycin failures in patients with wounds infected with P. multocida have resulted in serious complications, including septic arthritis, bacteremia and meningitis.(19)

The fluoroquinolones and some second- and third-generation cephalosporins, such as cefuroxime (Ceftin, Kefurox, Zinacef) and ceftriaxone (Rocephin), may provide adequate coverage but they have not been well studied. Although more expensive than the oral preparations, intramuscular or intravenous ceftriaxone may be useful when the degree of patient compliance is questionable or in instances in which rapid achievement of a high serum level is desired. Pregnant women and children who are allergic to penicillin are difficult to treat and often require a combination of two antibiotics. If erythromycin must be used, the patient’s progress should be monitored very carefully.

Most clinically infected bite wounds can be treated adequately using the same antibiotics that are used prophylactically, although the duration of treatment will vary. Cellulitis usually requires treatment with a 10- to 14-day course of antibiotics. Close follow-up for 24 to 48 hours after initiation of antibiotic therapy is recommended in all patients with a bite wound.

INPATIENT TREATMENT

Indications for hospitalization include systemic signs of infection, severe cellulitis, bone, joint, tendon or nerve involvement, lymphangitis, lymphadenitis, failure of appropriate oral antibiotic therapy and poor patient compliance. Consultation with an infectious disease specialist or referral to a plastic surgeon or orthopedic surgeon is often necessary in these serious cases.

RABIES IMMUNOPROPHYLAXIS

Since most domestic dogs have been vaccinated against rabies, the incidence of this disease in persons who have been bitten by a dog is quite low. Nonetheless, rabies is an extremely serious complication of animal bites: 16 deaths attributable to rabies were reported to the Centers for Disease Control between 1980 and 1990.(2)

The most common source of the rabies virus are wild animals, specifically raccoons, skunks and bats. Rabies may be transmitted when the saliva of an infected animal comes into contact with the broken skin or mucosa of another mammal; it is not necessary for a bite to occur. The incubation period ranges from 10 days to one year. Vaccination against rabies is prophylactic, not therapeutic. If rabies infection has been documented or a high degree of suspicion exists for infection, active immunization with human diploid rabies vaccine, 1 mL intramuscularly, is administered on days 0, 3, 7, 14 and 28.

The local health department should be contacted for information regarding rabies prevalence in a specific community. A 10-day surveillance of the animal suspected of biting is required.

TETANUS IMMUNIZATION

While tetanus infection resulting from cat and dog bites is rare, such cases have been reported. In the United States, elderly persons living in rural areas are the most likely to lack protective levels of tetanus antibodies.(20) Recommendations for tetanus prophylaxis are given in Table 5.(21)

[TABULAR DATA OMITTED]

Prevention

Simple measures, such as avoiding animals while they are eating, and exercising caution around strange animals, should prevent many bites.(3)(20)(22) In some communities, the local Humane Society provides educational workshops in schools. Parents of young children should be instructed to never leave the child alone with a pet regardless of the perceived disposition of the animal. Immunocompromised persons should be instructed to seek medical attention immediately if they are bitten or scratched. Several states have leash laws and restrictions on the ownership of vicious dogs.(20)(22) Community public health departments are usually responsible for the investigation of bites and the administration of laws regarding dangerous animals. Physician responsibility in reporting animal bites varies from state to state.

The authors thank William R. Scheibel, M.D., for reviewing the article, and Sutton Graham, III, M.D., for photographic assistance.

REFERENCES

(1.)Goldstein EJ. Bite wounds and infection. Clin Infect Dis 1992; 14:633-8.

(2.)Dire DJ. Emergency management of dog and cat bite wounds. Emerg Med Clin North Am 1992; 10:719-36.

(3.)Beck AM. The epidemiology and prevention of animal bites. Semin Vet Med Surg (Small Anim) 1991; 6:186-91.

(4.)Brook I. Human and animal bite infections. J Fam Pract 1989; 28(6):713-8.

(5.)Weber DJ, Hansen AR. Infections resulting from animal bites. Infect Dis Clin North Am 1991; 5:663-80.

(6.)Dire DJ. Cat bite wounds: risk factors for infection. Ann Emerg Med 1991; 20:973-9 [Published erratum appears in Ann Emerg Med 1992; 21:1008].

(7.)Kumar A, Devlin HR, Vellend H. Pasteurella multocida meningitis in an adult: case report and review. Rev Infect Dis 1990; 12:440-8.

(8.)Morris JT, McAllister CK. Bacteremia due to Pasteurella multocida. South Med J 1992; 85:442-3.

(9.)Holst E, Rollof J, Larsson L, Nielsen JP. Characterization and distribution of Pasteurella species recovered from infected humans. J Clin Microbiol 1992; 30:2984-7.

(10.)Hantson P, Gautier PE, Vekemans MC, Fievez P, Evrard P, Wauters G, et al. Fatal Capnocytophaga canimorsus septicemia in a previously healthy woman. Ann Emerg Med 1991; 20:93-4.

(11.)Kullberg BJ, Westendorp RG, van ‘t Wout JW, Meinders AE. Purpura fulminans and symmetrical peripheral gangrene caused by Capnocytophaga canimorsus (formerly DF-2) septicemia–a complication of dog bite. Medicine 1991; 70:287-92.

(12.)Chretien JH, Garagusi VF. Infections associated with pets. Am Fam Physician 1990; 41:831-45.

(13.)Myers RA, Littel ML, Joseph W. Bite wound infections of the lower extremity. Clin Podiatr Med Surg 1990; 7(3):506.

(14.)Dire DJ, Hogan DE, Walker JS. Prophylactic oral antibiotics for low-risk dog bite wounds. Pediatr Emerg Care 1992; 8:194-9.

(15.)Callaham M. Controversies in antibiotic choices for bite wounds. Ann Emerg Med 1988; 17:1321-30.

(16.)Wiley JF 2d. Mammalian bites. Review of evaluation and management. Clin Pediatr 1990; 29:283-7.

(17.)Hagan M, Goldstein E, Sanford JP. Bites from pet animals. Hosp Pract (Off Ed) 1993; 28:79-86.

(18.)Sanford JP. Case commentary. Hosp Pract (Off Ed) 1993:28:86,90.

(19.)Levin JM, Talan DA. Erythromycin failure with subsequent Pasteurella multocida meningitis and septic arthritis in a cat-bite victim. Ann Emerg Med 1990; 19:1458-61.

(20.)Avner JR, Baker MD. Dog bites in urban children. Pediatrics 1991; 88:55-7.

(21.)Diphtheria, tetanus, and pertussis: recommendations for vaccine use and other preventive measures. Recommendations of the Immunization Practices Advisory Committee (ACIP). MMWR Morb Mortal Wkly Rep 1991; 40(RR-10)1-28.

(22.)Wright JC. Canine aggression toward people. Bite scenarios and prevention. Vet Clin North Am Small Anim Pract 1991; 21:299-314.

RELATED ARTICLE: What to Do About a Cat or Dog Bite

How should I take care of a bite from a cat or a dog?

Here are some things you should do to take care of a wound caused by a cat or dog bite:

* Wash the wound gently with soap and water.

* Apply pressure with a clean towel to the injured part to stop the bleeding.

* Apply a sterile bandage to the wound.

* Keep the injury elevated above the level of the heart to slow swelling and prevent infection.

* Report the incident to the proper authority in your community (e.g., police or animal control office).

Should I call my doctor if I’ve been bitten by a cat or a dog?

Call your doctor in any of these situations:

* You have a cat bite. Cat bites are very prone to infection. You don’t need to call your doctor for a cat scratch, unless you think the wound is infected.

* You have a dog bite on your hand, foot or head, or you have another bite that is deep or gaping.

* You have diabetes, liver or lung disease, cancer or acquired immunodeficiency syndrome (AIDS), or other conditions that weaken your ability to fight infection.

* You have any signs of infection, such as redness, swelling, warmth, increased tenderness, oozing of pus from the wound, or fever.

* You have bleeding that doesn’t stop after 15 minutes of pressure or you think you may have a broken bone, nerve damage or other serious injury.

* Your last tetanus shot was more than five years ago. (If so, you may need a booster shot.)

What will my doctor do?

Here are some things your doctor may do to treat a cat or dog bite:

* Your doctor will examine the wound for possible nerve or tendon damage, or bone injury. He or she will also check for signs of infection.

* Your doctor will clean the wound with a special solution and remove any damaged tissue. (If you don’t need to see your doctor, you should still clean the wound with soap and water and apply antibiotic ointment to the area two times every day until it heals.)

* Sometimes stitches are used to close a bite wound, but often the wound is left open to heal, so the risk of infection is lowered.

* Your doctor may prescribe an antibiotic to prevent infection.

* Your doctor may give you a tetanus shot if you had your last shot more than five years ago.

* Your doctor will most likely want to check your wound again in one to two days.

* If your injury is severe, or if the infection has not gotten better even though you’re taking antibiotics, your doctor may suggest that you see a specialist and/or go to the hospital, where you can get special medicine given directly in your veins (intravenous antibiotics) and further treatment if necessary.

How can I prevent cat and dog bites?

Here are some things you can do to prevent bites:

* Never leave a young child alone with a pet.

* Do not try to separate fighting animals.

* Avoid strange and sick animals.

* Leave animals alone while they’re eating.

* Keep pets on a leash when you’re out in public with them.

* Select your family pet carefully.

This information provides a general overview on care of cat and dog bites and may not apply to everyone. Talk to your family doctor to find out if this information applies to you and to get more information on this subject.

This handout is provided to you by your family doctor and the American Academy of Family Physicians.

COPYRIGHT 1995 American Academy of Family Physicians

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