Cat-scratch disease: epidemiology, aetiology and treatment

Cat-scratch disease (CSD) is a clinical syndrome that usually presents as a self-limiting lymphadenopathy associated with a cat scratch or bite. Commo nly affecting children and young adults, it has a worldwide distribution. I n temperate climates, higher rates are reported in the autumn and winter, w hich can be attributed to the seasonal breeding of the domestic cat. The or ganism responsible was identified in 1983, having eluded detection for 50 y ears. Initially, Afipia felis was thought to be the cause; however, subsequ ent study failed to confirm a link. During the 1990s, it was demonstrated c onclusively that Rochalimaea henselae, later reclassified as Bartorzella he nselae, was the cause of CSD. B. henselae has been isolated from bacteraemi c cats, with transmission among cats thought to be via the cat flea. Althou gh other Bartonella species are transmitted by arthropod vectors, it is unl ikely that the cat flea is involved directly in human infection, but plays a role in amplifying the reservoir. B. henselae is difficult to culture, an d either serology or the polymerase chain reaction are considered to be the best methods of detection. Genetic variation occurs amongst B. henselae st rains, perhaps explaining the inconsistency of some diagnostic techniques. A separate serogroup (Marseilles) has been reported in a seronegative patie nt with CSD, and B. clarridgeiae has the potential to cause the disease. At ypical presentation is seen in up to 25% of cases, and manifests itself as ocular involvement, encephalopathy, granulomatous hepatitis, hepatosplenic infection, endocarditis and osteomyelitis. The majority of CSD cases resolv e spontaneously and do not require antibiotic treatment. In complicated CSD , treatment with trimethoprim-sulphamethoxazole, ciprofloxacin or azithromy cin is recommended, with gentamicin being reserved for the severely ill pat ient.