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Human and Animal Bites:

Human and Animal Bites:

Each year almost 5 million Americans sustain an animal or human bite.1-3 Dog bites alone represent 0.4% to 1% of all emergency department (ED) visits and can range from trivial to life-threatening.2,4-7

Victims of bite wounds are often emotionally distraught, whether from the severity of the injury, concern about the appearance of the wound, or the fact that their pet has just hurt them. Post-traumatic stress disorder is not uncommon among children who are bitten by dogs.8

You can do much to calm and reassure bite victims. Here we provide strategies that can minimize the risk of infection and disease and help ensure satisfactory wound healing.


Dog. There are 53 to 68 million domestic dogs in the United States.1,9,10 Dogs are responsible for 80% of all animal bites. Each year about 585,000 dog bites require medical attention, and 340,000 are managed in an ED.1,9,11 Most persons are treated and released; however, 2% to 4% require hospitalization, and approximately 20 deaths occur per year.1,7,9

Most fatal attacks involve children and are usually caused by an unrestrained dog on the dog owner's property.12 The typical dog-bite victim is a child, aged 5 to 9 years, who knows the biting animal and who has an extremity wound. Common offending breeds include rottweilers, chows, pit bulls, and German shepherds.3,9,12 In 80% of cases, the dog is known to the victim or family; in 70% of cases, the bite occurs in a familiar location.4,13 About 4% to 25% of dog bites result in infection, usually within 24 hours of the injury.4,6,10,11,14

Cat. More than 57 million cats are kept as pets in the United States; one is present in every third household.5 Cat bites represent between 3% and 15% of all animal bites. Most victims of cat bites are older women, and the bite usually occurs on the hand.4,5

Because cats have sharp, pointed teeth, their bite is likely to cause puncture wounds. From 30% to 80% of cat bites become infected, typically within 12 hours of the injury.4,5,11,14

Other animals. Although many other animals, such as primates, pigs, horses, and camels, can bite humans, only rodents represent a significant percentage of bite wounds (up to 7%). Ferrets, which have become popular pets, can attack humans, particularly small children.

Bites from animals other than dogs and cats often occur during job-related contact. In general, treat bites from these animals as you would treat dog and cat bites.3

Bites or scratches from rhesus and other macaque monkeys deserve special attention; these injuries usually occur in zoo or research laboratory workers. Monkeys can transmit herpesvirus simiae (B virus), which can cause fatal encephalitis. Acyclo-vir must be started immediately after exposure.15,16


Bites from humans occur during aggression, sports, and sexual activity.4 There are 2 distinct types: occlusion and clenched fist. An occlusion injury occurs when the perpetrator's teeth enter the victim's skin. The bite injury is on the victim. The wound poses a relatively low risk of infection.

A clenched fist injury (fight bite) occurs when someone strikes another person's mouth and teeth with a clenched fist. This results in a wound on the dorsum of the metacarpophalangeal joint.3,4 The bite injury is on the aggressor.

Clenched fist injuries can be severe and may have associated complications. Penetration of the joint capsule, for instance, occurs in 62% of cases and can result in tenosynovitis.3,6 Damage to the extensor tendon needs to be assessed and documented.3 A clenched fist injury can be difficult to diagnosis because patients often will not divulge the true mechanism of its occurrence. Maintain a high level of suspicion for this type of injury when treating patients with a laceration in the metacarpophalangeal region on the dorsum of the hand.

The infection rate associated with human bites ranges from 3% to 50%. Many human bites are already infected at the time of presentation.3

HIV and hepatitis virus can be transmitted via human bites when significant blood exposure occurs. According to CDC guidelines, HIV post-exposure prophylaxis (PEP) is indicated when either participant is HIV-positive or at high risk for the infection.

The risk of transmission of hepatitis B virus is greater than that of HIV. When one of the persons involved is infected, the other, if not previously vaccinated, should receive hepatitis B immune globulin (HBIG), 0.06 mL/kg IM, preferably within 24 hours of exposure, and the hepatitis B vaccine, 1 mL IM, on day 0 and at 1 month and 6 months. The effectiveness of HBIG after 7 days is not known. It is possible to wait for the results of hepatitis serologies if they are rapidly available. If the patient previously received hepatitis B vaccine, no PEP is necessary; however, if the vaccinated patient is known to be a nonresponder, offer HBIG.

There is no PEP for hepatitis C virus; however, it is helpful to identify those exposed to the virus, so they can be tested and observed.4 Check baseline HIV and hepatitis B and C levels every 6 months.3 More information can be obtained from the CDC PEP hotline at 888-448-4911 (Box).


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