Animal Bites in Infants and Children: An Approach to Diagnosis and Treatment
Author: Mary Jo A. Bowman, MD, Assistant Professor of Clinical Pediatrics, Ohio State University College of Medicine; Attending Physician, Emergency Department, Columbus Children’s Hospital, Columbus, OH.
Peer Reviewer: Norman C. Christopher, MD, Associate Professor and Chairman, Department of Emergency Medicine, Northeastern Ohio University College of Medicine; Director, Emergency Services, Children’s Hospital Medical Center of Akron, Akron, OH
Animal bites are a frequent problem encountered in the emergency department (ED). Infants and children may sustain serious injury as a result of an animal bite. Early recognition and timely management can minimize the morbidity and improve the long-term outcome associated with these injuries. Proper wound cleansing is critical for any animal bite and should be a primary concern in the ED. The judicious use of prophylactic antibiotics for high-risk wounds can also have a positive effect on the eventual outcome of an animal bite. The author presents a comprehensive review of animal bites and the controversies associated with their management.
—The Editor
Introduction
It is estimated that 2-4 million people are bitten by mammals each year in the United States.1-6 Most of these bites are minor and do not require medical attention. However, bite wounds still account for approximately 1% of all ED visits per year with 300,000-800,000 wounds requiring evaluation.3,4,7 In addition, there are 10,000 hospitalizations and 20 fatalities/year, with most of the deaths occurring in infants and small children.4,8,9 Significant morbidity may occur due to direct trauma, infection, or transmission of disease. Annual health care costs are estimated at $30 million with a recent study citing a price tag of $102 million per year.1,4
The purpose of this article is to review the evaluation and management of mammalian bites. An emphasis will be placed on those injuries caused by dogs, cats, and humans, as these account for the majority of bites. The epidemiology and microbiology of each species and risk factors for each species will be reviewed, specifically the diagnostic modalities, management strategies, wound care, and antibiotic usage. A discussion on the current Centers for Disease Control and Prevention (CDC) recommendations for rabies prevention will be presented.
Epidemiology
Dogs. Dog bites account for about 80-90% of animal bites each year.1,10-12 Children and young adults are bitten most frequently, with the highest incidence in the 5-14 year age group.10 A 1985 Pennsylvania survey determined that 46% of students had been bitten by a dog by the 12th grade.13 Boys are bitten twice as often as girls. Most attacks occur in the late afternoon-early evening hours of the summer months.
The dog is known to the victim about 90% of the time, residing either in the home or in the neighborhood.5,14-16 Dog bites are often provoked when the animal is defending its own territory, its food, or its puppies. Unprovoked attacks are also occurring as families acquire larger, more aggressive breeds for protection. Breeds most commonly implicated in bites are large dogs such as German shepherds, Doberman pinschers, and rottweilers.6,16,17 Bites from smaller breeds such as chows and Akitas are becoming more frequent.17 Pit bulls are the breed involved in most fatalities.8 Bites by strays are uncommon.
Other characteristics of dogs associated with biting, include male dogs, not neutered, large size (> 50 pounds) and young age (< 5 years). Many of the dogs were chained in the yard at the time of the attack.17
Dog bites most often occur on the extremities (54-85%), followed by the head and neck (15-27%) and rarely on the trunk (0-10%).11,14,18-20 In children younger than 4 years of age, bites of the head and neck predominate.21 Bites may be punctures, lacerations, avulsions, or abrasions. Fatal bites tend to occur in infants and young children. Deaths are, in general, attributable to exsanguination from the laceration of a major blood vessel that is the result of a bite around the head or neck.6,8,9
Dog bites have one of the lowest rates of infection, with an estimated 5-20% of bites becoming infected.5,12,14,22 This is most likely due to the fact that dog bites are often lacerations rather than punctures and are easier to clean and debride. The greatest risk of infection occurs with puncture wounds, crush injuries, and hand wounds.
Cats. Cat bites are the second most common type of mammalian bite, accounting for 5-15% of animal bites.1,11,14,16 The estimated incidence is thought to be about 400,000/year.11 A family pet inflicts the majority of bites. Cat bites tend to occur more frequently in girls, and the mean age of vicitims is older than dog bite victims.10
Studies show that 60-67% of cat bites occur on the upper extremity, 15-20% occur on the head and neck, 10-13% on the lower extremity, and 0-5% on the trunk.1,11,23 The teeth of a cat are slender and very sharp, resulting in deep punctures or scratches as the most common wounds. This, coupled with the fact that many bites occur to the hand, account for the higher infection rate (20-50%) seen with cat bites.1,5,14,24,25 Complications are also more likely to occur because the teeth often penetrate bones and joints.
Humans. Human bites account for 1-3% of all mammalian bites, making it the third most frequently encountered type of bite.1,26-28 Approximately 60-75% of bites occur on the upper extremity.1,10,28-30 There are two patterns of injuries seen in children.10,30 Accidental bites that occur during play or sports are often superficial and involve the face and upper extremity. Most of these wounds are evaluated by physicians within 12 hours of injury. Infection rates vary from 4-18%, comparable to infection rates seen in other bites and nonbite lacerations.29-31 The most serious type of human bite is the clenched-fist injury (fight bite). This injury occurs when the clenched fist contacts the tooth of another person, resulting in a puncture wound or laceration of the skin overlying the third metacarpophalangeal joint. This wound often results in perforation of the joint capsule. When the hand is held in extension, the wound is often overlooked, resulting in delays in seeking care or inadequate treatment. Infection rates of 50% or greater are seen with type of bite and complications are frequent.1,10,18,26
Microbiology
Dogs and Cats. (See Table 1.) Infections occurring after dog and cat bites are generally polymicrobial, with an average of 2-5 bacterial species isolated per culture.1,22,32,33 A more recent study by the Emergency Medicine Animal Bite Infection Study Group reported the median number of isolates per culture to be five.22 Infections contain both aerobes and anaerobes in the majority of cases, and are generally due to microorganisms found in the animal’s saliva. Normal skin flora are also found in infected wounds. Pasteurella sp. were responsible for about 50% of infections from dog bites and 75% of infections from cat bites in one study.22 Pasteurella canis predominates in dog bites and Pasteurella multocida is the most frequent organism found in cat bite infections. Pasteurella is a small gram-negative facultative anaerobic rod found in the oral cavities of one-half to two-thirds of dogs and cats. It produces a very characteristic pattern of infection with rapid onset of erythema and swelling, usually beginning within 24 hours of the injury, and often as early as 12 hours. There is an intense inflammatory response with local tenderness and severe pain in many instances. Regional adenopathy, fever, and lymphangitis develop in one-fourth to one-third of patients.
| Table 1. Microbiology of Bite Wounds—Most Common Pathogens | |
| Dogs and Cats | Humans |
| Pasteurella | Streptococcus sp. |
| Staphylococcus | Staphylococcus aureus |
| Streptococcus | Eikenella corrodens |
| Corynebacterium | Bacteroides |
| Fusobacterium | Fusobacterium |
| Bacteroides | Peptostreptococcus |
| Porphyromonas | |
| Prevotella | |
| ______________________________________________________ | |
Staphylococcus sp., Streptococcus sp., and Corynebacterium sp. are other common aerobic isolates from infected bite wounds.1,22,33-36 Anaerobes can be found in 38-76% of dog and cat bites, and include Fusobacterium, Bacteroides, Porphyromonas, and Prevotella.1,22,33 Anaerobes are generally found in mixed culture with aerobes. They are rarely the sole cause of infection in cultured bite wounds.
Capnocytophaga canimorsus (formerly Centers for Disease Control group DF-2) is a fastidious, gram-negative rod that is part of the normal oral flora in a number of dogs and cats. It has been identified as the organism responsible for a rare, but potentially fatal sepsis syndrome after dog bites. Approximately 80% of the cases are seen in immunocompromised hosts (asplenia, liver disease, and immunosuppressive therapy). Infection with this organism most often presents with overwhelming sepsis characterized by fever, petechiae, disseminated intravascular coagulation, and renal failure. Mortality is reported at 25%.37-39
Humans. At least 42 different species of bacteria have been reported in human saliva, with up to 190 species when gingivitis or periodontitis is present.1,10,33,34 Bacteriologic studies of human bites have almost all been of hand wounds. An average of five organisms had been found in cultured wounds, with a mix of aerobic and anaerobic bacteria.30,33 Organisms identified reflect the bacteriology of the skin flora of the victim and the oral cavity of the biter. The most frequent aerobic isolates are Streptococcus sp., Staphylococcus aureus, and Eikenella corrodens.33,34,40 Eikenella corrodens is a facultative, gram-negative rod found in approximately 25% of clenched-fist injuries that can cause a serious and chronic infection.41 Frequent anaerobes noted include Bacteroides, Fusobacterium, and Peptostreptococcus.33,34
Human bites can be broken down into two types when assessing infection risk—bites to the hand and all other bites. Studies in children have shown infection rates as low as 3.4%, probably due to the fact that the bites are likely to be superficial, don’t involve the hand, and are seen by a physician within 12 hours of the injury.31 A study of the natural course of human bites and nonbite lacerations that took place in an institution for the developmentally disabled showed an infection incidence of 17.7% for bite wounds vs. 13.4% for lacerations.42 The same study showed a twofold-increased risk of infection for hand wounds of any cause (bite or laceration). The higher incidence of infection in the hand is a function not only of the bacteriology of the wound but also of the anatomy of the hand itself.
Transmission of Systemic Disease
There are a number of zoonotic infections transmitted by dogs and cats either directly or indirectly. (See Table 2.) These include, but are not limited to, cat-scratch disease, tularemia, ehrlichiosis, brucellosis, toxoplasmosis, giardia, rabies, as well as flea bites and scabies.43,44
| Table 2. Transmission of Systemic Disease | |
| Dogs and Cats | Humans |
| Cat-scratch disease | Syphilis |
| Tularemia | Tuberculosis |
| Ehrlichiosis | Herpes virus |
| Brucellosis | Hepatitis B, C |
| Toxoplasmosis | |
| Giardia | |
| Rabies | |
| ___________________________________ | |
Cat-scratch disease is caused by Bartonella henselae, formerly known as Rochalimaea henselae. Kittens are more often implicated in transmission than cats as they have a tendency to be more playful and inflict scratches or bites. A primary papule appears at the site of inoculation approximately 7-10 days following exposure. Tender regional adenopathy appears about two weeks later. Systemic symptoms such as fever and malaise may be present in about 25% of cases. Unusual manifestations of this illness include encephalopathy, atypical pneumonia, parotid swelling, and granulomatous liver disease. The disease is usually self-limited with resolution in 2 or 3 months in most cases. Serologic testing may be done, although it is not species specific. A definitive diagnosis can be made via microscopy of lymph node biopsy. No antibiotic regimen has been shown to be consistently effective. Agents used include erythromycin, doxycycline, rifampin, ciprofloxacin, and aminoglycosides.10,43,45
Transmission of systemic illness via human bites has also been documented. Syphilis, tuberculosis, herpesvirus, and hepatitis B and C are known to cause illness after bites.1,26,44 A comment should be made regarding the possible transmission of human immunodeficiency virus (HIV). The presence of low levels of HIV has been detected in the saliva of as many as 44% of infected individuals.46 Two retrospective case reports of possible HIV transmission by a human bite have been published but have not shown unequivocal evidence of the nature of transmission.47,48 Prospective analysis and follow-up of patients bitten by HIV-infected persons shows such transmission to be unlikely.49,50
History
A number of historical features regarding the bite incident should be ascertained. (See Table 3.) The type and breed of the animal involved should be asked. This will help focus on the type of injuries and complications likely to be present. It also will help determine whether prophylactic antibiotics are to be used. Is the immunization status of the animal known? Vaccinated animals pose less risk for transmission of some diseases. What is the general health and behavior of the animal? Animals that are acting strangely or an unprovoked may prompt initiation of rabies immunization in the victim. What was the time of the event? Patients presenting later than 12 hours are at increased risk of infection. What were the circumstances surrounding the bite?
| Table 3. Historical Information |
| • Type and breed of animal
• Immunization status of animal • General health and behavior of animal • Time of the event • Circumstances surrounding the bite • Where is the animal now? • Sequence of events during the attack • Prehospital care • Immunization status of the victim • Allergy history of the victim _____________________________ |
Where is the animal now? The animal should be watched for 10 days for the development of any symptoms of rabies. Quarantining the animal may decrease the need for rabies prophylaxis of the victim. What was the sequence of events that occurred during the attack? Was the victim thrown down, shaken, or jumped on during the attack? These circumstances would increase the suspicion of more serious trauma and other injuries. What prehospital treatment took place? Immediate cleansing may decrease the risk of infection. Splinting and elevation help decrease swelling and subsequent morbidity. What is the victim’s immunization history? Does the patient have any allergies? Time of the last meal is also important for the patient who may need operative intervention. Does the patient have systemic disease that may increase the risk of infection (i.e., diabetes, asplenia, vascular disease, or immune deficiency)?
Physical Examination
Initial physical examination is directed at identifying any life-threatening injuries requiring resuscitation. Attention to Advanced Trauma Life Support (ATLS) principles takes precedence with attention to airway, breathing, and circulation.51 Major hemorrhage should be identified and controlled with direct pressure. Fully exposing the patient to look for all injuries is a must as some smaller wounds may be less obvious when there are major distracting injuries. Examination for direct injury (wound and adjacent structures) should be made as well as a thorough search for indirect injury (head injury and abdominal trauma secondary to a fall and/or being thrown).
The patient should be evaluated for visceral injury, especially in the case of infants and smaller children. Bony injuries should be ascertained and the patient evaluated for retained foreign bodies. In the case of injury to the extremities, distal neurovascular status should be evaluated and documented. Tendon or tendon sheath involvement should be noted as well as any evidence of joint space violation. Careful documentation of a complete extremity exam, especially in the case of clenched-fist injuries, should be undertaken. Documentation of the depth and length of the wound as well as tissue margin viability should be noted.
Diagnostic Modalities
Laboratory. Laboratory tests, in general, are not helpful in the acute management of animal bites.52 There is no indication for a CBC, white blood cell count, sedimentation rate, or other tests. In the case of systemic infection, these tests may be helpful in following the course of infection or sepsis. Baseline HIV testing with six-month follow-up may be indicated in at-risk human bites.
X-ray. X-rays may be useful in a number of clinical settings. These would include deep bite wounds of the hand, any suspected fight-bite injury, and cranial and facial bites in infants.1,10,52 Plain x-rays would be most useful in identifying fractures or retained foreign bodies (teeth). Infants are at high risk for cranial penetration in bite wounds about the face and head. Plain films, at the very least, are indicated to look for fracture. Computed tomography of the head can also be useful in identifying depression, fragments, foreign bodies, and intracranial bleeding associated with bites. (See Figure 1.) Special studies, such as arteriography, may be needed to evaluate major vascular structures if there is concern about injury to these areas.
Wound Cultures. Wound cultures are not indicated in fresh uninfected wounds;35 however, they are indicated in infected wounds, especially if the infection is resistant to initial antibiotic treatment. Cultures should also be indicated in patients who are immunocompromised. Both aerobic and anaerobic cultures should be done and laboratories should be notified of the nature of the culture, as some special arrangements may need to be made to process the sample properly.22 Cultures should be taken from as deep inside the wound as possible.
General Management
As with any trauma, the first priority of management is attention to the principles of ATLS: airway, breathing, and circulation.51 Most fatalities associated with animal bites are caused by acute hemorrhagic shock.8,9,12 Dog bites to the face, neck, and scalp area, especially in small children, may be associated with crush injuries to the larynx, massive hemorrhage occluding the airway, or even laceration of major blood vessels. Large or multiple scalp lacerations in infants can cause hypovolemia. Bleeding should be controlled by direct pressure and dressings. Attention should be given to the possibility of a cervical spine injury, especially if there is a history of shaking, throwing down, or knocking over of the victim. Once the life-threatening injuries have been taken care of, a more focused examination of the injuries can be done and further local wound management can take place.
Wound Management
Meticulous local wound care is the most important element in the management of animal bite wounds.1,10,52 Proper wound management helps decrease the incidence of infection and promotes satisfactory healing. Wound management includes cleaning and irrigation, debridement of devitalized tissue, closure, tetanus and rabies prophylaxis where indicated, judicious use of antibiotics, immobilization, and close follow-up.
Irrigation. The most important step in decreasing the risk of infection is proper wound cleansing. This should be done with copious amounts of sterile normal saline or Ringer’s lactate using a syringe and 19-gauge needle or catheter. This system generates high pressures that help reduce the bacterial inoculum and debride the wound.53 One study showed that proper irrigation alone decreased infection in dog bites from 69% to 12%.54 Several hundred ccs of fluid should be used. A 1% povidone-iodine solution (not the surgical scrub) can also be used in grossly contaminated wounds or those at high risk of rabies. This solution is bactericidal, fungicidal, and virucidal. Benzalkonium chloride is another solution that could be used if rabies is suspected.
Soaking the wound has not been adequately tested and may actually increase the risk of infection by redistributing bacteria in the fluid and thus the wound. The wound edges should be gently scrubbed with a surgical sponge with normal saline or 1% povidone-iodine solution.
Shaving the skin around the wound is not recommended. Infection may be increased due to microscopic nicks in the skin. If hair is a problem it can be clipped short with a pair of scissors.
Debridement. All devitalized tissue should be debrided. This removes bacteria, clots, soil, and other foreign matter from the wound. Debridement has been shown to decrease the dog bite wound infection rate thirty-fold in one study.55 It also creates new, cleaner wound edges that are easier to repair, heal faster, and in general, produces a smaller scar. The wound should be irrigated again once debridement is finished. However, debridement of puncture wounds is not recommended because it may lead to a larger defect that is harder to close.
Immobilization. Wounds occurring over joints, those associated with a fracture, and large areas should be elevated and immobilized. This is especially important in hand wounds, including clenched-fist injuries.
Tetanus Prophylaxis. Animal bites should be regarded as tetanus-prone. Clostridium tetani spores are found in soil, on teeth, and in the saliva of animals. Patients who have been previously immunized against tetanus but have not received a booster in the last 10 years should receive tetanus toxoid 0.5 mL intramuscularly. If the wound is a deep puncture, there is lots of devitalized tissue. If it is difficult to irrigate and debride, a tetanus toxoid booster should be given if the patient has not received a booster in the last five years. Patients who have never been immunized or whose immunization history is uncertain should receive tetanus immune globulin 250-500 U intramuscularly plus tetanus toxoid. Contraindications to tetanus immunization would include a history of severe hypersensitivity reaction or prior neurologic reaction to the vaccine.56
Wound Closure
Primary closure of animal bites is a less controversial subject than it was a number of years ago. Early consensus was that these wounds should never be sutured.57 Subsequent studies have shown good results with primary closure in low-risk bite wounds.53,54 (See Table 4.) In general, facial wounds should be primarily closed for cosmetic reasons.58-60 These bites are considered to be low-risk for infection because of the good vascular supply to this area. Large open lacerations may be closed primarily because of the ease of cleaning and debridement of this type of wound. Wounds seen within a few hours of injury, if not in a high-risk area, can be sutured. The longer the interval from time of injury to treatment, the higher the incidence of infection.
| Table 4. Low- vs. High-Risk Wounds |
| Low Risk |
Large lacerations |
| High Risk |
Punctures______________________________ |
Wounds that, in general, should not be primarily sutured because they are considered high-risk include: puncture wounds, extremity wounds (especially of the hand) wounds delayed in treatment (> 24 hrs.), cat bites, human bites (especially of the hand), and bites in immunocompromised patients.1,5,16,26
Puncture wounds are difficult to irrigate and clean adequately, due to deposition of bacteria deep in the wound. This is especially pronounced in bites from cats. Dogs may also cause puncture wounds, along with a crush type injury since they can exert as much as 450 psi during a bite. This leads to more devitalized tissue and deposition of bacteria, increasing the risk of infection.
Extremity bites, especially of the hand, are considered high risk for infection because these areas are so poorly vascularized. Tendon sheaths and other deeper structures can be penetrated, often without much evidence on physical examination. This is particularly true of the clenched-fist injury. Large gaping lacerations may be loosely approximated with sutures after vigorous cleaning and debridement. This allows for adequate drainage while maintaining cosmesis and function. Several studies have shown trends toward increased infection in hand bite wounds, with infection rates as high as 30-36% from dog bites.54,61 No large definitive study has yet been done, so it is prudent to err on the side of conservative treatment and not suture hand bite wounds.
Antibiotics
There is not another topic in bite-wound management that is more controversial than the prophylactic use of antibiotics in the treatment of animal bites. (See Table 5.) Consensus is evolving, though, as larger prospective studies are being done. Antibiotics given to prevent infection in bite wounds are not truly prophylactic because the injury and inoculum have already occurred. Surgical studies looking at the use of prophylactic antibiotics in patients undergoing major surgery have shown some value in certain high-risk cases, but only when antibiotics are given before the operation.62
| Table 5. Antibiotics for Bite Wounds | |
| Dog | |
| Dicloxacillin
Cephalexin Amoxicillin-clavulanic acid If PCN-allergic:
|
50-100 mg/kg/d in 4 doses
40-50 mg/kg/d in 2-3 doses 45 mg/kg/d in 2 doses 30-50 mg/kg/d in 3-4 doses
|
| Cat | |
| Amoxicillin-clavulanic acid
Cefuroxime axteil If PCN allergic:
|
45 mg/kg/d in 2 doses
20-30 mg/kg/d in 2 doses 15 mg/kg/d in 2 doses
|
| Human | |
| Amoxicillin-clavulanic acid
Cefuroxime axteil Cefixime If PCN allergic:
|
45 mg/kg/d in 2 doses
20-30 mg/kg/d in 2 doses 8 mg/kg/d in 1-2 doses 15 mg/kg/d in 2 doses
|
| __________________________________________________ | |
The mode of administration of the antibiotic also plays a role in the usefulness of the drug. Oral administration of antibiotics is less efficacious than parenteral routes. Intravenous administration is faster than the intramuscular route in obtaining useful wound concentrations of the antibiotics.63,64
The antibiotic itself differs in the time it takes to enter the wound. Penicillins, especially ampicillin, and cephalosporins are among the fastest antibiotics to achieve effective wound concentration. Erythromycin is somewhat slower, and tetracycline and clindamycin never achieve levels in the wound that match the serum concentration.64
Dogs. The vast majority of studies looking at the use of prophylactic antibiotics in bite wounds have been conducted on patients with dog bites. An early study in children looked at the use of penicillin given prophylactically in non-facial dog bite wounds. It showed a low incidence of infection in both penicillin and control (local wound care only) groups.36
Another study looked at the use of dicloxacillin, cephalexin, or erythromycin in low-risk dog bite wounds. Patients in this study were excluded if they had puncture wounds, hand or foot wounds, wounds greater than 12 hours old, or were on immunosuppressive drugs. One wound in the antibiotic group and five in the control group became infected. This was not statistically significant, and the authors concluded that routine use of prophylactic antibiotics in low-risk wounds is not warranted.65
Another study evaluated the use of amoxicillin/clavulanate vs. placebo in bite wounds and further broke down the groups into time of presentation after the injury. Those patients seen within the first nine hours after injury had no difference in wound infection, whereas those seen greater than nine hours post-injury had a lower incidence of infection if placed on antibiotics.66
There are many other studies in the literature that compare different antibiotics to each other or to placebo.67,68 Many of the studies are small or have small numbers of infections, making it difficult to meaningfully interpret the data. A meta-analysis was done recently that looked at eight randomized trials of prophylactic antibiotics for dog bite wounds. It re-emphasized that prophylactic antibiotics are not cost-effective for low-risk dog bites. It did demonstrate their appropriateness in high-risk wounds, including punctures, hand wounds, and wounds in immunocompromised patients.69
Which antibiotic to use is also controversial. Dicloxacillin or cephalexin will cover the majority of pathogens noted in dog bite wounds.52,70 These antibiotics are the least expensive as well. They do not have good coverage against Pasteurella, but this is less of a concern in dog bites than in cat bites. Cefuroxime axetil has good in vitro activity against most dog bite wound organisms but has not been clinically studied.71 Amoxicillin-clavulanic acid demonstrates adequate coverage both in vitro and clinically.32,66,71 Newer formulations of the clavulanic acid and twice-a-day dosing have decreased the incidence of undesirable antibiotic side effects, especially diarrhea, making this antibiotic a more palatable alternative. Ciprofloxacin and a number of other fluoroquinolones have good in vitro activity against most organisms and would seem a reasonable choice in teenagers with penicillin allergies.71,72 Erythromycin may be used in any penicillin-allergic group of patients and is cheaper than the fluoroquinolones. Two of the newer macrolides, clarithromycin and azithromycin, show promise in in vitro studies against some organisms, but, again, these have not been studied clinically.72
Current recommendations for dog bite wounds would include the following: 1) copious irrigation and debridement of all wounds; 2) antibiotics used prophylactically only in high-risk wounds, including puncture wounds, hand wounds, wounds greater than 12 hours old, and wounds in immunocompromised patients; 3) dicloxacillin or cephalexin are the antibiotics of choice with amoxicillin-clavulanic acid a good alternative; erythromycin or ciprofloxacin can be used in penicillin-allergic patients. Antibiotics are initially given for 3-5 days.
Cats. There is less controversy surrounding the use of prophylactic antibiotics for cat bites. Cat bites are at high-risk for infection because most of the wounds are on the hand and are punctures. Therefore, antibiotics are recommended by most authors.5,10,11,16 The controversy surrounds which antibiotic is most beneficial in the prophylaxis of cat bites. Cat bites have a high likelihood of infection from Pasteurella multocida.22 Penicillin is very effective against Pasteurella and shows better activity than dicloxacillin. However, penicillin alone is generally not recommended because of the potential for other pathogens to be present in the infection, especially Staphylococcus aureus. One effective regimen is oxacillin or cephalexin alone. Another would be penicillin and dicloxacillin together. Amoxicillin-clavulanic acid or cefuroxime axetil would be good choices as well, as they effectively cover Pasteurella.52,71 Penicillin-allergic patients could take erythromycin, although there have been several reports of resistance or poor results associated with the use of this antibiotic. The newer macrolides, clarithromycin and azithromycin, offer better alternatives, as shown in in vitro studies.72 Ciprofloxacin works well against Pasteurella and is a good alternative in penicillin-allergic adult patients.71,72
Current recommendations for cat bite wounds would include the following: 1) copious irrigation and debridement of all wounds; 2) prophylactic antibiotics for all but the most trivial bites; 3) an antibiotic to cover Pasteurella such as amoxicillin-clavulanic acid, cefuroxime axetil, or a newer macrolide or ciprofloxacin in penicillin-allergic patients. Antibiotics are given for 3-5 days.
Humans. Human bites have a high incidence of infection in most studies due to the clenched-fist injury. Studies done on children who have sustained simple occlusional bites not on the hand or other high-risk areas show no increased incidence of infection over other animal bites.26,29,30 Antibiotic prophylaxis is therefore recommended for the same indications as other animal bites. Antibiotics are definitely indicated for clenched-fist injuries. Human bites present special problems with antibiotic coverage. While gram-positive aerobic bacteria such as Streptococcus and Staphylococcus predominate, Eikenella corrodens is found in approximately 7-29% of human bite hand infections.1,26,41 Eikenella has been shown to be resistant to dicloxacillin, clindamycin, many first-generation cephalosporins, and, now, even penicillin. Antibiotics that provide good coverage include amoxicillin-clavulanic acid, cefuroxime axetil, and cefixime.52,71 Ciprofloxacin can be used in the penicillin-allergic adolescent patient and clarithromycin or azithromycin in the younger pediatric patient.71,72
Current recommendations for human bite wounds would include the following: 1) copious irrigation and debridement; 2) antibiotic prophylaxis for all but the smallest occlusional bites; 3) antibiotic coverage to include not only gram-positive aerobes but also Eikenella corrodens—amoxicillin-clavulanic acid, cefuroxime axetil, or cefixime; ciprofloxacin, clarithromycin or azithromycin in the penicillin-allergic patient. Antibiotics may be given for 3-5 days initially.
Consultation
Subspecialty consultants may be needed to help care for the patient who presents with animal bite injuries. A trauma or general surgeon should see any child who presents with exsanguinating hemorrhage, multisystem injuries or has the potential for severe underlying injuries. The decision to operate needs to be made early to avoid potential complications. An infant or child with a penetrating skull injury from an animal bite should be seen by a neurosurgeon. Debridement and/or elevation of a depressed skull fracture may be needed.
A pediatric patient with extensive wounds, especially of the face or those with tissue loss or involvement of complex structures may require consultation and evaluation by a plastic surgeon. Open wounds with underlying fractures need evaluation by an orthopedic surgeon. Patients with clenched-fist injuries often require referral to or consultation with a hand surgeon. These patients should be closely followed.
Follow-up
Following evaluations and treatment of an animal bite, it is important that the patient has close follow-up and good home-going instructions. Patients who sustain superficial abrasions need not follow-up routinely but should have good instructions on watching for signs of infection. Those patients who sustain a low-risk bite should be seen in follow-up within 48 hours. Generally only one follow-up visit is needed. Any patient who has a high-risk wound (hand, puncture, cat or human, immunocompromised) should be seen in follow-up within 24 hours. These patients generally will need to be seen daily for 2-3 days.
Complications
Wound infection is the most common complication seen with animal bites.10,52 Localized cellulitis and abscess formation are the most common forms of infection. The diagnosis of wound infection can be made when there is increased erythema, swelling, tenderness of the wound margins, and/or purulent drainage. More extensive local infection may occur and consist of cellulitis, lymphangitis, or local adenopathy. Treatment of wound infection would include elevation and immobilization (if on an extremity), removal of sutures, cleansing, and antibiotic therapy. Cultures of the wound, if done, should be from as deep in the wound as possible and should be sent for both aerobic and anaerobic cultures. Empiric antibiotic coverage should be started based on the principles outlined in the previous section on prophylactic antibiotics and guided by culture results. Surgical debridement may be needed in the case of abscess formation.
A number of other complications may be seen secondary to animal bites, although these are not as common as wound infection. (See Table 6.) They include septic arthritis, osteomyelitis, sepsis, endocarditis, tenosynovitis, and meningitis.44,52 The ED physician should be aware of the potential for complications and carefully instruct patients on signs and symptoms and appropriate follow-up. Most patients with these more severe complications will require hospitalization.
| Table 6. Complications |
| • Localized cellulitis
• Abscess formation • Septic arthritis • Tenosynovitis • Osteomyelitis • Sepsis • Endocarditis • Meningitis ___________________ |
When to Admit
Most patients with animal bites will neither require hospitalization nor suffer from complications. Patients with an infection who exhibit fever or systemic symptoms or who are not responding to outpatient antibiotics should be admitted and started on intravenous antibiotics. Patients who present with signs of a deeper or more serious infection (i.e., septic arthritis, tenosynovitis, osteomyelitis) should also be admitted to the hospital for further care. Immunocompromised patients with local cellulitis should be considered candidates for admission as their potential for sepsis is increased. Patients with hand wounds with known involvement of bones, joints, or tendons should be strongly be considered for admission, as infection in these areas can cause significant morbidity.
Rabies Immunoprophylaxis
Many families seek care following an animal bite because of concern regarding possible rabies transmission. Rabies results in about 35,000 deaths per year worldwide.73 In the United States, only 32 cases have been reported from 1980-1996.73 This is due to effective animal control and vaccination programs as well as access to medical care and postexposure prophylaxis (PEP).
Dogs are the major animal reservoir for rabies worldwide. Few dogs in the United States, however, have rabies, except along the Mexican border. The animals most noted to have rabies in the United States are raccoons, skunks, foxes, and bats.73,74
The newest Advisory Committee on Immunization Practices (ACIP) recommendations place ferrets in the group with domestic dogs and cats rather than wild carnivores.74 Routine rabies PEP is not needed in the case of a ferret bite.
When an animal bite has occurred, two questions need to be asked. 1) Did an exposure occur? 2) Was the animal rabid?
Rabies is transmitted through the saliva of the infected animal when the virus is introduced into a bite wound or open cut in the skin or onto mucous membranes of the victim.75 Any penetration of the skin by teeth constitutes a bite exposure. A nonbite exposure occurs when there is contamination of open wounds, mucous membranes, or abrasions by the saliva of a potentially rabid animal. Petting a rabid animal or coming in contact with blood, urine, or feces of a rabid animal does not constitute an exposure.74
The likelihood of rabies in a domestic animal in the United States varies by region. Consultation with the local health department is helpful in determining this risk. A healthy dog or cat that bites a person can be confined and observed for 10 days. PEP is not warranted. If any signs of rabies develop, the animal should be euthanized, and its head should be tested for rabies at a qualified laboratory.
There has been a change in ACIP recommendation with regard to PEP in potential bat exposures. PEP should be considered when direct contact between a human and a bat has occurred. A minute bite or scratch may be missed on examination so PEP should be considered for persons found in the same room as a bat who may not be aware of contact (e.g., an unattended child, a mentally disabled person, or a sleeping person who awakens to find a bat, ).74,76,77
PEP should be given to patients bitten by wild carnivores, including raccoons, skunks, foxes, and coyotes. In general, rodents and lagomorphs (rabbits and hares) are almost never found to be infected with rabies. The exception is groundhogs (woodchucks) in areas where raccoon rabies is enzootic. The state or local health department may be consulted in these areas.74,75
PEP includes the administration of both rabies immune globulin (RIG) and rabies vaccine. RIG provides antibodies until the patient responds to the vaccine. It is recommended for both bite and nonbite exposures, regardless of the interval between exposure and initiation of treatment. It may be given up to seven days after the first dose of vaccine if not given simultaneously. It should not be used in a previously vaccinated individual. The dose of RIG is 20 IU/kg. In the past, half of the dose was given at the bite site (if anatomically feasible) and half at a distant site from the vaccine. New recommendations are to give the full dose (or as much as possible) at the site of the bite.74 The remainder may be given at a site distant from the vaccine.
Three rabies vaccines are available for use in the United States. Human Diploid Cell Vaccine (HDCV) and Rabies Vaccine Adsorbed (RVA) have been in use for a number of years. Purified Chick Embryo Cell Vaccine (PCEC) became available in the United States in late 1997.74 Any of the products may be used. Five 1 ml doses of vaccine should be given intramuscularly, with the first dose given as soon as possible after exposure. The remaining doses are given on days 3, 7, 14, and 28 after the first vaccination. Previously vaccinated individuals should receive two doses of vaccine on days 0 and 3. The preferred choice of site for vaccination is the deltoid area in adults and older children. The anterolateral thigh area is also acceptable, especially in small children. The vaccine should never be given in the gluteal region as this results in lower neutralizing antibody titers.
Local wound care with soap and water and either povidone-iodine or benzalkonium chloride solution helps decrease the likelihood of infection.
Summary
Animal bites are a frequent problem seen in the ED and can cause significant morbidity and mortality. Meticulous wound care with copious irrigation and debridement are the hallmarks of treatment. Wound closure and antibiotic use need to be determined on a case-by-case basis. It is useful to place the wound in a high- vs. low-risk group to determine the need for further treatment. Close follow-up and a watchful eye for infection are essential for outpatient management and reduction of potential litigation.
References
1. Griego RD, Rosen T, Orengo IF, et al. Dog, cat, and human bites: A review. J Am Acad Dermatol 1995;33:1019-1029.
2. Voelker R. Dog bites recognized as public health problem. JAMA 1997;277:278-280.
3. Sacks JJ, Kresnow M, Houston B. Dog bites: How big a problem? Injury Prevention 1996;2:52-54.
4. Weiss HB, Friedman DI, Coben JH. Incidence of dog bite injuries treated in emergency departments. JAMA 1998;279:51-53.
5. Baker MD. Bites and scratches: When pets fight back. Contemp Pediatr 1989;6:76-84.
6. Brogan TV, Bratton SL, Dowd MD, et al. Severe dog bites in children. Pediatrics 1995;96:947-950.
7. Sosin DM, Sacks JJ, Sattin RW. Causes of nonfatal injuries in the United States, 1986. Accid Anal Prev 1992;24:685-687.
8. Sacks JJ, Lockwood R, Hornreich J, et al. Fatal dog attacks, 1989-1994. Pediatrics 1996;97:891-895.
9. Centers for Disease Control and Prevention. Dog-bite related fatalities—United States, 1995-1996. JAMA 1997;278:278-279.
10. Wiley JF. Mammalian bites: review of evaluation and management. Clin Pediatr 1990;29:283-287.
11. Garcia VF. Animal bites and Pasteurella infections. PIR 1997;18:127-130.
12. Goldstein EJC. Bite wounds and infection. Clin Infect Dis 1992;14:633-640.
13. Beck AM, Jones BA. Unreported dog bites in children. Public Health Rep 1985;100:315-321.
14. Kizer KW. Epidemiologic and clinical aspects of animal bite injuries. J Am Coll Emer Med 1979;8:134-141.
15. Lauer EA, White WC, Lauer BA. Dog bites: A neglected problem in accident prevention. Am J Dis Child 1982;136:202-204.
16. Rosekrans JA. Animal bites: A summertime hazard. Contemp Pediatr 1993;10:23-32.
17. Gershman KA, Sacks JJ, Wright JC. Which dogs bite? A case-control study of risk factors. Pediatrics 1994;93:913-917.
18. Kelleher AT, Gordon SM. Management of bite wounds and infection in primary care. Clev Clin J Med 1997;64:137-141.
19. Presutti RJ. Bite wounds: Early treatment and prophylaxis against infectious complications. Postgrad Med 1997;101:243-254.
20. Underman AE. Bite wounds inflicted by dogs and cats. Vet Clin North Am 1987;17:195-207.
21. Chun Y, Berkelhamer JE, Herold TE. Dog bites in children less than 4 years old. Pediatrics 1982;69:119-120.
22. Talan DA, Citron DM, Abrahamian FM, et al. Bacteriologic analysis of infected dog and cat bites. N Engl J Med 1999;340:85-92.
23. Dire DJ. Emergency management of dog and cat bite wounds. Emerg Med Clin North Am 1992;10:719-736.
24. Aghababian RV, Conte JE. Mammalian bite wounds. Ann Emerg Med 1980;9:79-83.
25. Elenbaas RM, McNabney WK, Robinson WA, et al. Evaluation of prophylactic oxacillin in cat bite wounds. Ann Emerg Med 1984;13:155-157.
26. Callaham M. Controversies in antibiotic choices for bite wounds. Ann Emerg Med 1988;17:1321-1330.
27. Hodge D, Tecklenburg FW. Mammalian bites. In: Fleisher GR, Ludwin S, et al, eds. Textbook of Pediatric Emergency Medicine. 3rd ed. Baltimore: Williams & Wilkins; 1993:853-857.
28. Marr J, Beck A, Lugo J. An epidemiologic study of the human bite. Public Health Rep 1979;95:514-521.
29. Baker MD, Moore SE. Human bites in children: A six-year experience. Am J Dis Child 1987;141:1285-1290.
30. Leung AK, Robson WL. Human bites in children. Pediatr Emerg Care 1992;8:255-257.
31. Schweich P, Fleischer G. Human bites in children. Pediatr Emerg Care 1985;1:51-53.
32. Goldstein EJC, Reinhardt JF, Murray PM, et al. Outpatient therapy of bite wounds: Demographic data, bacteriology, and a prospective, randomized trial of amoxicillin/clavulanic acid versus penicillin + dicloxacillin. Int J Dermatol 1987;26:123-127.
33. Brook I. Microbiology of human and animal bite wounds in children. Pediatr Infect Dis J 1987;6:29-32.
34. Goldstein EJC, Citron DM, Wield B, et al. Bacteriology of human and animal bite wounds. J Clin Microbiol 1978;8:667-672.
35. Ordog GJ. The bacteriology of dog bite wounds on initial presentation. Ann Emerg Med 1986;15:1324-1329.
36. Boenning DA, Fleisher GR, Campos JM. Dog bites in children: Epidemiology, microbiology, and penicillin prophylactic therapy. Am J Emerg Med 1983;1:17-21.
37. Mellor DJ, Bhandari S, Kerr K, et al. Man’s best friend: Life threatening sepsis after minor dog bite. BMJ 1997;314:129-130.
38. Hovenga S, Tulleken JE, Moller LVM, et al. Dog-bite induced sepsis: a report of four cases. Intensive Care Med 1997;23:1179-1180.
39. Hantson P, Gautier PE, Vekemans M-C, et al. Fatal Capnocytophaga canimorsus septicemia in a previously healthy woman. Ann Emerg Med 1991;20:126-127.
40. Goldstein EJC. Infections following human bites. Infect Surg 1985:849-859.
41. Schmidt DR, Heckman JD. Eikenella corrodens in human bite infections of the hand. J Trauma 1983;23:478-482.
42. Lindsey D, Christopher M, Hollenbach J, et al. Natural course of the human bite wound: Incidence of infection and complications in 434 bites and 803 lacerations in the same group of patients. J Trauma 1987;27:45-48.
43. Tan JS. Human zoonotic infections transmitted by dogs and cats. Arch Intern Med 1997;157:1933-1943.
44. Edward, MS. Infections due to human and animal bites. In: Feigin RD, Cherry JD, eds. Pediatric Infectious Diseases. Philadelphia: WB Saunders; 1987:2362-2373.
45. Jaffe AC. Animal bites. Ped Clin North Am 1983;30:405-413.
46. Groopman JE, Salahuddin SZ, Sarngadharan MG, et al. HTLV-III in saliva of people with AIDS-related complex and healthy homosexual men at risk for AIDS. Science 1984;226:447-449.
47. Wahn V, Kramer HH, Voit T, et al. Horizontal transmission of HIV infection between two siblings. Lancet 1986;2:694.
48. Anonymous. Transmission of HIV by human bite. Lancet 1987;2:522.
49. Richman KM, Rickman LS. The potential for transmission of human immunodeficiency virus through human bites. J Acquir Immune Defic Syndr 1993;6:402-406.
50. Tsoukas CM, Hadjis T, Schuster J, et al. Lack of transmission of HIV through human bites and scratches. J Acquir Immune Defic Syndr 1988;1:505-507.
51. Initial assessment and management. In: Advanced Trauma Life Support for Doctors: Student course manual. 6th ed. Chicago;1997: 21-46.
52. Callaham ML. Bites and injuries inflicted by mammals. In: Auerbach PS, ed. Wilderness Medicine: Management of Wilderness and Environmental Emergencies. 3rd ed. St. Louis: Mosby; 1995:927-993.
53. Zook EG, Miller M, Van Beek AL, et al. Successful treatment protocol for canine fang injuries. J Trauma 1980;20:243-247.
54. Callaham ML. Treatment of common dog bites: Infection risk factors. J Am Coll Emer Med 1978;7:83-87.
55. Callaham ML. When an animal bites. Emerg Med 1988;20:120-134.
56. Centers for Disease Control and Prevention. Tetanus prophylaxis. MMWR Morb Mortal Wkly Rep 1981;30:392-407.
57. Lee JLH, Buhr AJ. Dog bites and local infection with Pasteurella species. BMJ 1960;248:169-171.
58. Guy RJ, Zook EG. Successful treatment of acute head and neck dog bite wounds without antibiotics. Ann Plastic Surg 1986;17:45-48.
59. Kountakis SE, Chamblee SA, Maillard AA, et al. Animal bites to the head and neck. ENT J 1998;77:216-220.
60. Wolff, KD. Management of animal bite injuries of the face: Experience with 94 patients. J Oral Maxillofac Surg 1998;56:838-843.
61. Callaham ML. Prophylactic antibiotics in common dog bite wounds: A controlled study. Ann Emerg Med 1980;9:410-414.
62. Maki DG. Lister revisited: Surgical antisepsis and sepsis. N Engl J Med 1976;294:1286-1287.
63. Alexander JW, Alexander SE. Influence of route of administration on wound concentrations of prophylactic antibiotics. J Trauma 1976;16:488-495.
64. Alexander JW, Sykes NS, Mitchell MM. Concentration of selected intravenously administered antibiotics in experimental surgical wounds. J Trauma 1973;13:423-434.
65. Dire DJ, Hogan DE, Walker JS. Prophylactic oral antibiotics for low-risk dog bite wounds. Pediatr Emerg Care 1992;8:194-199.
66. Brakenbury PH, Muwanga C. A comparative double blind study of amoxycillin/clavulanate vs placebo in the prevention of infection after animal bites. Arch Emerg Med 1989;6:251-256.
67. Rosen RA. The use of antibiotics in the initial management of recent dog-bite wounds. Am J Emerg Med 1985;3:19-23.
68. Jones DA, Stanbridge TN. A clinical trial using co-trimoxazole in an attempt to reduce wound infection rates in dog bite wounds. Postgrad Med J 1985;61:593-594.
69. Cummings P. Antibiotics to prevent infection in patients with dog bite wounds: A meta-analysis of randomized trials. Ann Emerg Med 1994;23:535-540.
70. Callaham ML. Prophylactic antibiotics in dog bite wounds: Nipping at the heels of progress. Ann Emerg Med 1994;23:577-579.
71. Goldstein EJC, Citron DM. Comparative activities of cefuroxime, amoxicillin-clavulanic acid, ciprofloxacin, enoxacin, and ofloxacin against aerobic and anaerobic bacteria isolated from bite wounds. Antimicrob Agents Chemother 1988;32:1143-1149.
72. Goldstein EJC, Citron DM, Hudspeth M, et al. Trovafloxacin compared with levofloxacin, ofloxacin, ciprofloxacin, azithromycin and clarithromycin against unusual aerobic and anaerobic human and animal bite-wound pathogens. J Antimicrob Chemother 1998;41:391-396.
73. Noah DL, Drenzek CL, Smith JS, et al. Epidemiology of human rabies in the United States, 1980 to 1996. Ann Inter Med 1998;128:922-930.
74. Centers for Disease Control and Prevention. Human rabies prevention—United States, 1999 recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR Morb Mortal Wkly Rep 1999;48(RR-1):1-21.
75. Fishbein DB, Robinson LE. Rabies. N Engl J Med 1993;329: 1632-1638.
76. Centers for Disease Control and Prevention. Human rabies—Montana and Washington, 1997. MMWR Morb Mortal Wkly Rep 1997; 46:770-774.
77. Centers for Disease Control and Prevention. Human rabies-Texas and New Jersey, 1997. MMWR Morb Mortal Wkly Rep 1998;47:1-5.
Physician CME Questions
Which of the following statements is true?
a. Most dog bites are from strays
b. Dog bites, in general, have a higher incidence of infection than cat bites
c. Head and neck dog bites are more common in smaller children than adults
d. Akitas cause most dog bite fatalities
Which of the following is not one of the most common bacteria in dog or cat bite infections?
a. Pasteurella
b. Streptococcus
c. Eikenella
d. Staphylococcus
Which of the following antibiotics would not be indicated for prophylaxis of bite wounds in the pediatric patient?
a. dicloxacillin
b. ciprofloxacin
c. amoxicillin-clavulanic acid
d. erythromycin
The most important aspect of wound management in animal bites is:
a. antibiotic use
b. soaking the wound
c. immobilization
d. copious irrigation
What is the most common complication of animal bites?
a. septic arthritis
b. endocarditis
c. osteomyelitis
d. local wound infection
Indications for hospital admission would include all of the following except:
a. immunocompromised patient with local cellulitis
b. patient with local infection and systemic symptoms
c. patient with osteomyelitis
d. patient with localized abscess
Which of the following is not a common vector for rabies in the United States?
a. bats
b. skunks
c. dogs
d. raccoons
Which of the following statements about rabies is true?
a. New recommendations include giving as much of the full dose of rabies immune globulin as possible at the site
b. Most dogs and cats carry rabies in the United States
c. Ferrets are to be considered as wild carnivores, warranting postexposure prophylaxis
d. A patient who was previously immunized against rabies requires 5 injections
Correction
In the April 1999 issue of Pediatric Emergency Medicine Reports, Acute Presentation of Muscle Weakness, the following items should be included:
Table 2, Weakness: Differential Diagnosis: Under neurologic heading—Cranial nerve palsies, Other peripheral nerve palsies, Stroke, and Multiple sclerosis; under Psychosocial heading, Child Abuse—Munchausen Syndrome by proxy.
Table 7: The title Tonic Neck Reflexes should read Evolution of Neck Reflexes.
We apologize for any confusion this may have caused.
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