An enlarged lymph node in the armpit region of a person with cat scratch disease, and partially healed wounds from a cat scratch on the hand.
Cat scratch disease (CSD) is a bacterial infection spread by cats. The disease spreads when an infected cat licks a person’s open wound, or bites or scratches a person hard enough to break the surface of the skin. About three to 14 days after the skin is broken, a mild infection can occur at the site of the scratch or bite. The infected area may appear swollen and red with round, raised lesions and can have pus. A person with CSD may also have a fever, headache, poor appetite, and exhaustion. Later, the person’s lymph nodes near the original scratch or bite can become swollen, tender, or painful.
Wash cat bites and scratches well with soap and running water. Do not allow cats to lick your wounds. Contact your doctor if you develop any symptoms of cat scratch disease or infection.
CSD is caused by a bacterium called Bartonella henselae. Up to 30% of cats carry B. henselae in their blood, although most cats with this infection show NO signs of illness. Kittens younger than 1 year are more likely to have B. henselae infection and to spread the germ to people. Kittens are also more likely to scratch and bite while they play and learn how to attack prey.
How cats and people become infected
Kitten playing with a person's fingers.
Cats can get infected with B. henselae from flea bites and flea dirt (droppings) getting into their wounds. By scratching and biting at the fleas, cats pick up the infected flea dirt under their nails and between their teeth. Cats can also become infected by fighting with other cats that are infected. The germ spreads to people when infected cats bite or scratch a person hard enough to break their skin. The germ can also spread when infected cats lick at wounds or scabs that you may have.
Serious but rare complications
People
Although rare, CSD can cause people to have serious complications. CSD can affect the brain, eyes, heart, or other internal organs. These rare complications, which may require intensive treatment, are more likely to occur in children 5-14 years of age and people with weakened immune systems.
Cats
Most cats with B. henselae infection show NO signs of illness, but on rare occasions this disease can cause inflammation of the heart—making cats very sick with labored breathing. B. henselae infection may also develop in the mouth, urinary system, or eyes. Your veterinarian may find that some of your cat’s other organs may be inflamed.
