What Is Cat Scratch Disease?

Medical Author: Melissa Stoppler, MD
Medical Editor: Barbara K. Hecht, PhD

Cat scratch disease is an infection caused by bacteria known as Bartonella henselae. Although about 40% of cats carry the bacteria in their saliva at some point in their lives, cats that carry Bartonella henselae do not themselves show any signs of illness. Most people contract the disease after being scratched or bitten by a cat.

Since these bacteria may also be present on cat fur, it is possible to contract the disease from petting a cat and then rubbing your eyes. Kittens are more likely than older cats to carry the bacteria and to transmit the infection to humans. Sometimes people who get cat scratch disease do not recall ever being scratched or bitten by a cat.

In people who have a normal immune system, cat scratch disease is usually not a serious illness. A small papule (a little raised lump) develops at the site of injury within 10 days. The signs and symptoms that follow may include:

Medically Reviewed by a Doctor on 12/1/2014