Domestic animals, such as dogs and cats, are responsible for the majority of animal bites. While dogs cause more bite injuries, cat bites are more likely to become infected. Infection happens in about 1 percent of dog bites and between 5 and 10 percent of cat bites (ASSH). One reason that animal bites often lead to infection is that bites frequently occur on the fingers or hands, where the body may have a harder time fighting infection. Animal bite infections are serious and can even be life-threatening.
These infections are often caused by bacteria penetrating the skin. The bacteria may come from the animal’s mouth or may be present on the skin. As the bacteria multiply, the body’s immune response causes common symptoms of infection (swelling and inflammation, for example).
Animal bites that don’t break the skin are not at risk for infection. Scrapes or scratches that just graze the skin’s surface have a minimal risk of infection. Cuts or lacerations have a higher risk of infection. Puncture wounds, especially those caused by a cat, are considered to have the highest risk of infection.
Cat teeth can cause deep puncture wounds that are hard to clean thoroughly. Since the teeth are very sharp, a wound can be deep but small and can heal over quickly. This can trap bacteria inside the wound.
In very rare cases, bites caused by wild animals such as bats, raccoons, foxes, and wild dogs can cause rabies infections. Rabies is a potentially life-threatening illness. Seek medical attention for any wild animal bite that breaks the skin’s surface.
Clean all animal bites thoroughly. Monitor all animal bites and seek medical attention if signs of an infection develop.
(This information is a summary. Always seek medical attention if you are concerned you may be experiencing a medical emergency.)
The most common symptoms of infection from animal bites are redness, pain, swelling, and inflammation at the site of the bite.
Other symptoms of infection include:
- pus or fluid oozing from the wound
- tenderness in areas near the bite
- loss of sensation around the bite
- if the hand was bitten, limited use of the finger or hand
- red streaks near the bite
- swollen lymph nodes
- fever or chills (flu-like symptoms)
- breathing difficulties
- muscle weakness or tremors
Infection from animal bites is caused by bacteria in the mouth or saliva of the animal, bacteria present on the skin that enters the wound, or bacteria present in the environment. Animal bites are often polymicrobial, which means that multiple species of bacteria are involved. Tetanus, a bacterial disease affecting the nervous system, can develop from these bacteria and is a serious condition. Puncture wounds from animal bites are the most likely to lead to tetanus.
To diagnose infection from an animal bite, your doctor will ask about the bite, including what kind of animal it was, what prompted the bite, and whether the animal has had a rabies vaccine. He or she will also ask when you last had a tetanus shot.
Your doctor might also order an X-ray to determine whether the infection has spread to the bone, especially if the bite is on the finger or hand. Blood tests can also diagnose a spreading of the infection, known as sepsis. Sepsis and infection of the bone are life-threatening concerns.
The first step with an animal bite is to properly clean and assess the wound. This could help prevent infection in an animal bite.
If an infection develops, your doctor will prescribe antibiotics. Your doctor might also suggest a tetanus booster.
If left untreated, infection from animal bites could spread and cause serious medical problems. Infection generally develops within 24 to 48 hours.