On this page
Short answer When a cat scratch needs a doctor Common questions Related questions Sources**Cat scratch disease is caused by a bacterium called Bartonella henselae, which cats carry in their blood and pass to people through a scratch, bite, or a lick on broken skin.**
Cats become carriers after infected fleas bite them and leave flea dirt in their fur, which the cat then rubs into its own claws and mouth while grooming. Most infected cats look completely healthy, so there is no way to tell by looking which animal is carrying the bacteria. Kittens under one year old and cats with fleas are the most likely sources, and about 1 in 3 people with the illness recall a scratch or bite in the two weeks before symptoms start. Keeping cats on year-round flea control, washing any scratch with soap and running water right away, and avoiding rough play that leads to bites cut the risk substantially. The infection does not pass from person to person.
When a cat scratch needs a doctor
Common questions
What causes cat scratch disease?
Cat scratch disease comes from Bartonella henselae bacteria. Cats pick the bacteria up from infected fleas and flea dirt, then carry it in their blood, usually without appearing sick. You get infected when a cat scratches or bites hard enough to break the skin, or licks an open wound or scab. Kittens and stray cats are the most common sources. A small bump or blister often forms at the scratch site within 3 to 14 days, followed by swollen, tender lymph nodes near that area, sometimes with fever, headache, and tiredness. Most cases clear on their own, but see a clinician if the lymph nodes stay swollen, the wound looks infected, or you have a weakened immune system.