Assessing and Managing Mammal Bites – an Article Review

 Updated 3/2017-- all links (except to my own posts) removed as many no longer active. and it was easier than checking each one.

Not sure how I got on the list to receive Emergency Medicine journal, but I always look through it before I recycle it.  There are often decent articles in it.  The one referenced below is a nice quick review on the problem of mammal bites.  This is an issue most doctors will encounter at some point in time.

About 1% of emergency department and urgent care visits each year are for mammal bite injuries or their complications. Ten to 20 people die each year from mammal bites. In 2006, 310,710 injuries from dog bites alone were reported to the Centers for Disease Control and Prevention. The actual number of bite wounds from all mammals is estimated to be around 2 million each year, but that figure underestimates the true incidence because most animal bites are unreported.

Animal bite injuries come in many forms:  lacerations, punctures, crush injuries, tears, rips, avulsions, fractures, hemorrhage, and contusions. The type and severity of the injury will depend on the location of the bite, the animal involved, and size of the patient. 

More than two-thirds of bite injuries occur in children younger than 10 years old—boys more often than girls. Children most commonly pre-sent with bite wounds to the face, neck, and head. Adults more commonly present with bites to the extremities.

The article gives helpful “History and Physical Exam Tips”

• Patients usually seek medical care for repair of the wound or because the wound has become infected.

A thorough history of the event includes asking about the timing of the injury, the kind of animal involved, its health history (including vaccination status and current health), and its behavior. Other important information about the animal includes whether it can be observed or captured.

• Thoroughly examine patients with bites.  Especially with children, check the entire body to identify additional injuries.
• Examine the wound itself meticulously. It’s easy to miss things.
• Be alert for injuries to the vasculature, nerves, tendons, bones, and joints.
• Bites from large mammals can damage and even fracture bone.  Plain radiographs should be viewed after the exam.
• Large mammals who bite and shake can dislocate joints. Have patients perform active range-of-motion with joints that are near bite wounds.
• Use plain radiography to assess for retained foreign bodies and skeletal injuries. Computed tomography and magnetic resonance imaging have increased sensitivity for foreign bodies and subtle fractures.

The article gives a nice review of principles for reducing the risk of infection.   As with all wounds, standard wound care applies.  This means copiously irrigate and debride as needed.
Bites are tetanus-prone wounds. Review the patient’s immunization records.  Give updates, etc as needed.
Most wounds can be closed primarily.  It’s expected that a small percentage of wounds will become infected and require early suture removal. Inform patients that wound infections may occur in spite of the appropriate care. Advise all patients at discharge to look for signs of infection, such as redness, increasing pain, and purulent drainage.
Some bite wounds have a higher risk of infection.

Animal Bites With a High Risk for Infection
•  crush injuries
•  hand wounds
•  puncture wounds
•  wounds with extensive devitalized tissue
•  heavily contaminated wounds
•  prolonged time from injury to treatment:
     6–12 hours on the body
     12–24 hours on the face

The article points out some specific considerations to keep in mind.

Dog bites. A big fear with dog bites is rabies, but the actual incidence among these dogs in the United States is low.  Similarly, few dog bites actually lead to infection. 

However, significant bites are at risk for infection, which is usually polymicrobial. About 50% of infected dog bites involve Pasteurella canis. The first-line antibiotic is amoxicillin/clavulanic acid 875 mg orally twice daily for adults and 10 to 15 mg/kg orally three times daily for children (see table below). Duration of therapy is not clearly established.

Cat bites. In contrast to dog bites, most cat bites do become infected.

Pasteurella multocida is present in 70% to 90% of the infections. Antibiotic post-exposure prophylaxis that is effective for P. multocida is recommended for all cat bites; unfortunately, P. multocida is resistant to clindamycin, dicloxicillin, cephalexin, and erythromycin. The first-line antibiotic is amoxicillin/clavulanic acid 875 mg orally twice daily in adults, 10 to 15 mg/kg orally three times daily for children. Duration of therapy is not clearly established.

Cats have the highest incidence of rabies of all domestic animals in the United States. However, transfer to humans remains rare. 

Primate bites.  A subgroup of primates called the macaques (rhesus and green monkeys) carry B virus (Cercopithecine herpesvirus 1), usually by the age of 2.

Though asymptomatic in the macaques, B virus causes fatal encephalitis in humans; 24 of the 25 humans known to be infected have died. The incidence of transmission is unknown, but it has been documented to occur from even trivial wounds. Due to the high mortality, post-bite prophylaxis is recommended for any macaque bite. First-line therapy is valacyclovir 1 gram orally every 8 hours for 14 days.

Rodent and rabbit bites. Rodents, rabbits, and hares carry Francisella tularemia and can transmit this to humans through bites. The CDC does not recommend routine prophylaxis for tularemia from the bite of a rodent.

Domestic and wild rats in the United States carry and transmit Streptobacillus moniliformis, which causes rat bite fever. The CDC recommends post-bite prophylaxis after wild or domestic rat bites.The first-line antibiotic is amoxicillin/clavulanic acid 875 mg orally twice daily for adults and 10 to 15 mg/kg orally three times daily for children. Duration of therapy is not clearly established.

Overall, a very nice review article.  Especially good for students and residents.  The article includes tables of appropriate antibiotics and dosages.

Related Blog Posts:

Cat Bites

Dog Bite Prevention

REFERENCE
Assessing and Managing Mammal Bites; Emerg Med 41(1):35, 2009; Lisa D. Mills, MD, and John Lilley, MD