General Information: Bartonella clarridgeiae was first identified from a case of cat scratch fever in a veterinarian who had been bitten by a cat. This organism has subsequently been identified in both cats and dogs. Cats, which are infected by fleas carrying the bacteria, in turn infect humans when scratching or biting them, hence the name. A small red bump forms at the site of infection, followed 2-3 weeks later by a painful swelling of the lymph node. In immunocompromized patients, more severe progress may be observed, including encephalitis, swelling of the spleen, and heart valve infection. Approximately 24 000 cases are reported in the US each year.