ABSTRACT
INTRODUCTION The history of African tick-bite fever, probably an ancient disease in sub-Saharan Africa, contains several phases of scientific confusion. The first human cases were described almost 100 years ago in Mozambique and South Africa (1). At that time, however, the disease was confused with Mediterranean spotted fever caused by Rickettsia conorii and it was not until the mid-1930s that Pijper, a pathologist working in Pretoria, thoroughly described the distinct epidemiology and clinical picture of African tick-bite fever (2). More importantly, Pijper was also able to isolate the causative agent and demonstrated that it differed from R. conorii using cross-protection studies. Unfortunately, his isolate and data were later lost, and subsequent scientists were unable to reproduce Pijper’s findings. As a result, African tick-bite fever was again erroneously recognized as a mere variant of Mediterranean spotted fever, and the observed difference in clinical presentation and epidemiology between the two entities were attributed to different host factors, such as age and risk behavior (3). The final breakthrough came several decades later, in 1992, when a spotted-fever group rickettsia was isolated in the blood of a 36-year-old Zimbabwean woman who presented with typical African tick-bite fever (4). This isolate was distinct from R. conorii, but indistinguishable from rickettsial strains isolated in Amblyomma ticks collected in Ethiopia and Zimbabwe some 20 years earlier (5,6); the species was later named Rickettsia africae. This newly identified species was later named R. africae (7).
