Bartonella henselae (Classical Cat Scratch Disease)

• Considered a relatively benign, self-limiting disease in people. Frequently, an inoculation papule, which can persist for months, is located at the site of a bite or scratch. Intermittent fever, lymphadenopathy and lethargy may be the only clinical manifestations of B. henselae. Approximately 10% of currently recognized B. henselae cases are accompanied by atypical manifestations, including tonsillitis, encephalitis, endocarditis, cerebral arteriosis, transverse myelitis, granulomatous hepatitis and/or splenitis, osteolysis, pneumonia, pleural effusion, and thrombocytopenic purura. Until recently, physicians would not have considered bartonella infection in the differential diagnosis of patients with atypical B. henselae manifestations, particularly if a history of lymphadenopathy or animal contact was not obtained. Infection with B. henselae can produce distinct clinical entities in immunocompromised people, including acute febrile illness with bacteremia, bacillary angiomatosis, peliosis hepatis, bacillary splenitis, and other chronic disease manifestations such as AIDS encephalopathy.
• The diagnosis of bartonella infection should be confirmed by culturing the organism or amplifying DNA from tissues, such as lymph node or spleen, using PCR. B. henselae are intraerythrocytic bacteria, therefore cell lysis, using a lysis centrifugation technique, greatly facilitates bacterial isolation from blood. Bacteria in the genus Bartonella are very fastidious, requiring up to 60 days to identify bacterial colonies. Seroconversion, using IFA or ELISA, can be used to confirm a diagnosis in people with acute disease.
• Because of disparate results among studies and an overall lack of microbiologic data in clinical therapeutic trials, numerous issues related to treatment of human bartonella infection remains controversial. In contrast to the apparent lack of response to antimicrobial treatment in human B. henselae patients, bacillary angiomatosis, parenchymal bacillary peliosis, and acute bartonella bacteremia appear to respond to antimicrobial treatment, particularly in immunocompromised individuals. Doxycycline, erythromycin, and rifampin are recommended antibiotics, but clinical improvement has been reported following the use of penicillin, gentamicin, ceftriaxone, ciprofloxacin, and azithromycin.
• Although a source of serious morbidity, infection with Bartonella species is an extremely rare cause of human mortality. Following a cat scratch or bite, the skin should be cleansed thoroughly with soap and warm water. If an inoculation papule develops, a physician should be consulted.