Cat scratch fever: An infection caused by the Bartonella henselae bacteria. Almost half of all domestic cats carry these bacteria and can transmit it to humans through a scratch or bite. Cat scratch fever causes swelling of the lymph nodes, sore throat, fatigue, fever, chills, sweats, vomiting, loss of appetite, and weight loss. There is usually a little bump (a papule), which may be pus-filled (a pustule), at the site of the scratch. In people with immunodeficiency, cat scratch fever can progress to bacillary angiomatosis, a bacterial skin infection.