Tick bite fever in black South Africans--a rare disease?

Tick bite fever (Rickettsia conorii) is a disease which occurs commonly in South Africa. Clinical illness in the black African patient is however rare, despite high seroprevalence rates of antibodies against R. conorii reported from other areas of Southern Africa. We present two case reports of clinically apparent tick bite fever occurring in black South Africans, the first to be documented in sub-Saharan Africa, and examine possible explanations for the marked discrepancy between clinical illness and seroprevalence rates.