Epidemiology

During the past 3 decades, there have been approximately 20 deaths per year in the USA from dog-inflicted injuries; 65% of these occurred in children younger than 11 yr. The breed of dog involved in attacks on children varies; Table 705-1 depicts the risk index by breed from one study of 341 dog bites. Rottweilers, pit bulls, and German shepherds accounted for more than 50% of all fatal bite-related injuries. Unaltered male dogs account for approximately 75% of attacks; nursing dams often inflict injury to humans when children attempt to handle one of their puppies.

Table 705-1 RISK OF DOG BITES AMONG CHILDREN IN THE USA, BY DOG BREED

The majority of dog-related attacks occur in children between the ages of 6 and 11 yr. Boys are attacked more often than girls (1.5 : 1). Approximately 65% of the attacks occur around the home, 75% of the biting animals are known by the children, and almost 50% of the attacks are said to be unprovoked. Similar statistics apply in Canada, where 70% of all bites reported in one study were sustained by children between 2 and 14 yr; 65% of the dogs involved in the biting were part of the family or extended family and occurred in someone’s home.

Of the approximately 450,000 reported cat bites per year occurring in the USA, nearly all are inflicted by known household animals. Because rat bites and gerbil bites are not reportable conditions, little is known about the epidemiology of these injuries or the incidence of infection after rodent-inflicted bites or scratches.

Few data exist on the incidence and demographics of human bite injuries in pediatric patients; however, preschool and early school-aged children appear to be at greatest risk of sustaining an injury from a bite by a human. Human bites are a common cause of injury in daycare centers in the USA, although in some series the proportion of human bites is highest among adolescents. In adolescents, fist-to-mouth (tooth) injuries are associated with fights.

Clinical Manifestations

Dog bite–related injuries can be divided into three, almost equal categories: abrasions, puncture wounds, and lacerations with or without an associated avulsion of tissue. Dog bites may be crush injuries. The most common type of injury from cat and rat bites is a puncture wound. Cat bites often penetrate to deep tissue. Human bite injuries are of two types: an occlusion injury that is incurred when the upper and lower teeth come together on a body part and, in older children and young adults, a clenched-fist injury that occurs when the injured fist, usually on the dominant hand, comes in contact with the tooth of another individual.

Diagnosis

Management of the bite victim should begin with a thorough history and physical examination. Careful attention should be paid to the circumstances surrounding the bite (e.g., type of animal [domestic or sylvatic], whether the attack was provoked or unprovoked, location of the attack); a history of drug allergies; and the immunization status of the child (tetanus) and animal (rabies). During physical examination, meticulous attention should be paid to the type, size, and depth of the injury; the presence of foreign material in the wound; the status of underlying structures; and, when the bite is on an extremity, the range of motion of the affected area. A diagram of the injury should be recorded in the patient’s medical record. A radiograph of the affected part should be obtained if there is likelihood that a bone or joint could have been penetrated or fractured or if foreign material is present. The possibility of a fracture or penetrating injury of the skull should be considered in individuals, particularly infants, who have sustained dog bite injuries to the face or head.

Complications

Infection is the most common complication of bite injuries, regardless of the species of biting animal. The decision to obtain material for culture from a wound depends on the species of the biting animal, the length of time that has elapsed since the injury, the depth of the wound, the presence of foreign material contaminating the wound, and whether there is evidence of infection. Although potentially pathogenic bacteria have been isolated from up to 80% of dog bite wounds that are brought to medical attention within 8 hr after the bite, the infection rate for wounds receiving medical attention in <8 hr is small (2.5-20%). Thus, unless they are deep and extensive, dog bite wounds that are less than 8 hr old do not need to be cultured unless there is evidence of contamination or early signs of infection or the patient is immunocompromised. Species of Capnocytophaga canimorsus, uncommon pathogens in bite-inflicted injuries, have been isolated from nearly 5% of infected wounds in immunocompromised patients. The infection rate in cat bite wounds that receive early medical attention is at least 50%; therefore, it is prudent to obtain material for culture from all but the most trivial cat-inflicted wounds and from all other animal bite wounds that are not brought to medical attention within 8 h, regardless of species of the biting animal.

The rate of infection after rodent bite injuries is not known. Most of the oral flora of rats is similar to that of other mammals; however, approximately 50% and 25% of rats harbor strains of Streptobacillus moniliformis and Spirillum minus, respectively, in their oral flora. Each of these agents has the potential to cause infection (Chapter 705.1).

All human bite wounds, regardless of the mechanism of injury, should be regarded as carrying high risk for infection and should be cultured. Because of the high incidence of anaerobic infection after bite wounds, it is important to obtain material for anaerobic as well as aerobic cultures.

Common causes of soft tissue bacterial infections after dog, cat, or human bites are noted in Table 705-2. High risk for infection after a bite is associated with wounds in the hand, foot, or genitals, penetration of bone or tendons, human or cat bites, delay in treatment longer than 24 hr, presence of foreign material, immunosuppression (asplenia), and crush or deep puncture wounds.

Treatment (Table 705-3)

After the appropriate material has been obtained for culture, the wound should be anesthetized, cleaned, and vigorously irrigated with copious amounts of normal saline. Irrigation with antibiotic-containing solutions provides no advantage over irrigation with saline alone and may cause local irritation of the tissues. Puncture wounds should be thoroughly cleansed and gently irrigated with a catheter or blunt-tipped needle; high-pressure irrigation should not be employed. Avulsed or devitalized tissue should be debrided and any fluctuant areas incised and drained.

Table 705-3 PROPHYLACTIC MANAGEMENT OF HUMAN OR ANIMAL BITE WOUNDS TO PREVENT INFECTION

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