Souvenir from South Africa

Excerpt

A 47-year-old male presented with fever of 39 °C, headache, and malaise that had begun upon his return from a vacation in South Africa. Five days previously, he had developed a painless violaceous plaque with a central eschar over the right popliteal fossa after having attended a wildlife safari. No insect bite was remembered. Further examination revealed palpable, painless inguinal lymphadenopathy. Routine laboratory tests showed an elevated C-reactive protein (1.46 mg/dl), with no other abnormal parameters. Histology revealed ulcerated necrosis accompanied by a dense lymphohistiocytic infiltrate, with signs of vascular injury in the superficial and deeper dermis, including intramural and perivascular infiltration with endothelial swelling and vascular fibrinoid necrosis (Figs. 1 and 2). Serology revealed IgG antibodies against Rickettsia sp. using an indirect immunofluorescence assay (IFA; Fuller Laboratories, Fullerton, CA, USA), and Rickettsia sp.-specific DNA was identified from the biopsy specimen by polymerase chain reaction (PCR) using a primer for the citrate synthase gene (gltA all rickettsiae) and confirmed the species R. rickettsii by Sanger sequencing. Based on these findings, the diagnosis of African tick bite fever was established. The patient received doxycycline 100 mg orally twice a day for 10 days and achieved complete clinical remission. Rickettsia are Gram-negative bacteria, first described by Howard Ricketts in 1906. They are transferred by arthropod vectors, most commonly ticks, and cause a variety of clinical presentations, combining fever and cutaneous eruptions [1, 2]. Rickettsia infections are endemic to sub-Saharan regions, the Far East, and the Americas. They are exceedingly rare in northern and central Europe, but an increase in global tourism and mobility may well lead to more frequent encounters with this condition [3].

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