Also known as cat scratch fever this disease is likely more an issue for people than cats. Cat scratch disease is caused by the bacteria Bartonella henselae which is spread by fleas. Typically what happens is a flea infested cat scratches himself, gets a claw full of flea dirt and then scratches a human or another cat.
In humans a reddened bump can develop around the scratch and a few weeks later lead to swelling of the local lymph node with associated fever and pain. Often, these symptoms resolve on their own. Much more serious conditions can occur in immunocompromised people such as those with a positive HIV status.
Up to 40% of cats in areas with fleas are infected, but it is fairly controversial whether or not any actual disease processes are associated with infection. There are several ways to test cats for Bartonella but all have pros and cons. Given that no one is sure about the clinical relevance of this organism in cats a diagnosis is rarely pursued. However a course of antibiotics may be tried and can clear up to 83% of cats so this may be a viable alternative to testing in cats where Bartonella is suspected of contributing to clinical disease.
Prevention in cats is primarily use of routine flea control. Prevention in humans is via thorough cleansing of any cat scratches. Prophylactic use of antibiotics after a cat scratch has not been shown useful.