Animal Bites

Bites are extremely common and can cause significant pain and may rapidly progress to infection and stiffness in the hand.  Early and appropriate treatment is key to minimizing potential problems from a bite. 

When an animal bites, bacteria from its mouth contaminate the wound.  These bacteria then may grow in the wound and cause infection.  The result of the infection ranges from mild discomfort to life-threatening complications. 

Many factors contribute to development of an infection, including the type and location of the wound, pre-existing health conditions in the bitten person that impair their immunity (such as diabetes, vascular disease, cancer, HIV), delay in treatment, the presence of a foreign body in the wound (such as a chip off a tooth), and the type of animal that bit the individual.

Animal Bites
The majority of animal bites in the U. S. are caused by dogs, with cat bites a distant second.  Other biting animals include rodents, rabbits, ferrets, farm animals, monkeys, snakes, alligators, and in coastal areas, marine animals (shark, eel).  Infections occur more frequently in cat bites, because they have extremely sharp, pointed teeth that can cause deep puncture wounds.  These bites are often much deeper that initially appreciated, even by the bitten individual.  The skin usually flaps over the bite, sealing off the puncture wound, precluding open drainage and allowing an infection to develop (see Figure 1).

The major concern of all bite wounds is subsequent infection.  In the United States, about 1% of dog bites and about 5-10% of cat bites require hospitalization.  With swift and proper care, the prognosis is usually very good for recovery from these injuries. 

Rabies is an extremely rare but fatal infection that may result from an animal bite.  In the United States, unlike the rest of the world, wild animals such as bats, skunks, raccoons, and foxes spread more than 90% of rabies infections.   Animal bites should be reported to your local health department.  They may ask your assistance in locating the animal so that it can be confined and observed for symptoms of rabies.

Human Bites (Clenched fist injury)
Human bite wounds contain very high concentrations of bacteria so the risk of infection is high.  These infections can progress rapidly and result in substantial complications, so early treatment is necessary (see Figure 2).  Often, human bites occur when a person’s fist is driven into another person’s mouth, such as during a fistfight.  After the skin is broken, bacteria are seeded into the soft tissue and often into the “knuckle” joint, which if left untreated often results in deep infection of the joint that may ultimately destroy the joint.  The extensor tendon is often cut by the victim’s tooth.  The tooth may even break and be left in the wound.  Early diagnosis, intravenous antibiotics, and surgery to drain the infection and wash out the joint can effectively treat these injuries.

Symptoms of Concern with Bites to the Hand 
If the bite wound results in swelling, redness, warmth and continued pain beyond 24 hours, pus draining from the bite wound, red streaks extending up the arm or forearm, swollen lymph nodes (“glands”) around the elbow or in the armpit, loss of mobility, loss of sensation in the hand or fingertip, fever, loss of energy, night sweats, or chills, emergency treatment should be sought either in your physician’s office or the emergency room.
 
Treatment of Bites
Your doctor will examine the bite wound and ask about contributing factors to the injury.  A complete history of the bite, including the type of animal and its health (behavior and rabies vaccine status), the time and location of the event, circumstances of the bite, whereabouts of the animal, and the pre-hospital treatment will be reviewed.  It is crucial to update your tetanus status if you have not had a booster shot within the past five years.  X-rays may be used to identify any damage to the bones and joints or tooth fragments that may have broken off.  If an infected bite to the hand goes untreated for too long, X-rays may reveal evidence of osteomyelitis, which is infection in the bone.

Animal bites to the hand require meticulous cleansing.  Your doctor or other medical personnel will wash the wound and might trim away any devitalized (dead) tissue, damaged skin, blood clots, or other particles that could be a source of infection.  It is important to look for signs of lymphangitis, indicated by the presence of red streaks up the forearm.  When the wound is infected, a culture is obtained to identify the type of bacteria that is causing the infection and thus help determine the antibiotic that is most effective for treatment.

The use of antibiotics for animal bites depends on the particular circumstances of the injury, patient health, and sensitivity to various medications, and the appearance of the wound.  Some bites require the use of intravenous (IV) antibiotics, while others may be treated with oral medications.  The presence of an underlying fracture usually dictates inpatient antibiotic treatment.  If you are diagnosed as having an infection of a flexor tendon sheath or joint, you will need to have hand surgery, which would need to be performed as soon as possible.

Follow-up care is crucial in the case of animal or human bite wounds, to ensure that infection is diminishing or has not developed, and to restore the hand as best as possible to its former condition.  These injuries should be taken seriously to prevent poor function of your hand.

 

Figure 1:  Finger infection from cat bite

 


Figure 2:  Wound infection of a thumb tip after a human bite.

 

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© 2006 American Society for Surgery of the Hand

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