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August 28, 2014 at 9:54 AMComments: 1 Faves: 0

Animal Bites: What You Need To Know

By Jeffrey VanWingen M.D. More Blogs by This Author

Photo Credit: Vaughan Nelson@flickr

I saw a patient this week following a long hospitalization.  It all began when she spotted an innocent looking and cute looking cat in her yard.  An animal lover, she approached the cat hoping to provide some nourishment as it looked rather thin.  She held out her hand with some food as a gesture of good will.  The cat approached for the food and at the last minute panicked, biting her on the hand.  "It was just a scratch," she said.  The food was left on the back porch and she cleaned the wound before going to bed.  A couple days later, the whole hand was red and swollen.  She had also developed a fever.  I took one look at it and sent her to the hospital.  Here she was, after surgery and days of IV antibiotics.  "I had no idea a tiny nip from a cat could be so bad." 

Animal bites cause about 10-20 fatalities in America each year.  On an average year, around 4.7 million ER visits will be logged.  About 2% of these cases will require a stay at the hospital for treatment.  Dogs account for 85-90% of recorded bites and occur mostly in children.  Cats account for 5-10% and occur mostly in adult women.

This blog will cover animal bites - when and when not to worry.

(Bites - for consideration here - are those that break the skin and cause bleeding. )

Consider the Bite Source

Bites can be worrisome or not worrisome based on the animal doing the biting. Basically, bites from carnivores (meat eaters) are of more concern. These animals have teeth that are more pointy than herbivores (plant eaters).  While herbivores have flat, broad teeth for grinding plant matter, most all animals that eat meat have pointy teeth to rip and tear flesh.  This design and any meat remnants in the teeth harbor bacteria that can cause infection. Further, a bite from a carnivore causes more damage by puncturing and tearing, injecting the bacteria deeper into the flesh.  This makes it more difficult for the process of bleeding and subsequent cleaning to remove all the infection-causing bacteria. 

Cats: Of carnivorous animal bites, cat bites are much more prone to become infected because of their sharp pointed, arcing canine teeth.  As a general guideline, it is a good idea to get all cat bites looked at for cleaning and preventative antibiotics.

Dogs and Other Meat-Eating Creatures: With dogs and other carnivore bites, good cleaning is important and the decision for antibiotics can be determined based on severity. 

Herbivores: Bites from plant eaters are at low risk for infection and can just be observed following a good cleaning.  It is important to remember that humans are carnivores too.  Any human bite has a reasonable chance of becoming infected, probably at about the same risk as a dog.

Other Circumstances to Consider

The location of the bite on the body and other susceptibilities can play an important role in determining seriousness. 

Hands: Bites involving the hand are common and considered more serious. Tendons and bones lie just below the skin and can become easily involved in the bite. When the bite extends into these tissues, the potential for serious infection skyrockets.  As such, any bite on the hand should be explored by a medical professional. Similarly, bites near and artificial joint should be treated with increased care.

Extent of Damage: Bites with significant tissue damage are more serious. 

Auto-Immune or Diabetes: Lastly, predisposing conditions that may affect healing and warding off infection should be considered such as a weakened immune system, poor nutrition or diabetes.

When to Think About Shots

Most animal bites involve pets.  It is important to know or inquire about vaccination status in the biting animal.  In most states, it is required by law that pets be properly vaccinated, namely for rabies. Rabies, a virus that can infect any mammal, is universally fatal when it becomes symptomatic.  On average, there are less than eight human cases per year in the U.S.  In animals, about 6-7,000 cases are reported each year.

Wild Animals: Any bite from a wild animal or an unvaccinated pet animal should prompt consideration for getting a preventative rabies vaccine. With bats, the presence of a bat in the room while a person has been asleep is reason enough to consider vaccination. 

Dogs and Cats: While the most common cases occur in raccoons, bats and skunks it has been reported in dogs and cats.

Rabies immune vaccine is given in the ER and is a four dose series.  Like any injury through the skin, tetanus should also be considered.  If childhood tetanus series has been complete, a booster within the last 10 years is considered adequate for minor wounds and within the last five years for more significant wounds.

Cleaning a Bite Wound

In the event of a bite, encourage it to bleed (within reason).  This helps to cleanse the wound of debris and bacteria.  Use antiseptic and water to wash the tissue.  It is best to use a catheter with a syringe to squirt sterile saline with pressure into the wound for better clearing of bacterial presence.

In general, bites from carnivorous animals are considered "dirty" and should heal from the inside out. This generally means that closing the would without stiches is best.  With more significant wounds, however, and wounds to the face, the burden of scaring is outweighed by the potential for infection.  In these cases, stitching up the wound is fine, but antibiotics should be given to cover for the increased potential for infection.

Prevention and social considerations

Safety around animals occurs on both sides of the leash so to speak.  Animals should be approached with caution.  Children should be taught to not approach domesticated or wild animals who are strange to them.  Sudden or aggressive moves should not be made around even well known animals as a general rule.  For pet owners, protective equipment should be used in public if the animal is not completely trustworthy.  

Animal bites are a common occurrence.  Some bites are more risky than others.  Carnivorous animals, primarily cats, are at high risk of becoming infected.  Bites on the hand are the most concerning.  Considerations for rabies and tetanus should also be given for all bites.  


Dog and Cat Bites: American Family Physician, August 15, 2014; volume 90 No. 4   

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