African tick-bite fever: four cases among Swiss travelers returning from South Africa.

BACKGROUND: African tick-bite fever (ATBF) is a recently described disease belonging to the spotted fever group. It is caused by Rickettsia africae, and cases are mainly diagnosed in travelers returning from sub-Saharan Africa.

METHODS: We report four cases of ATBF among Swiss travelers returning from a 1-month trip in rural South Africa. Diagnosis was made on the basis of clinical, epidemiologic and serologic findings that we describe in detail. Serology was performed using microimmunofluorescence (MIF) assay 2 weeks, 6 weeks and 14 months after the commencement of symptoms.

RESULTS: All patients developed the typical eschar and a rash; two had a local lymphadenopathy and one a lymphangitic reaction. Two patients developed transient neuropsychiatric symptoms such as headache, irritability and depressed mood. All four patients had rises in both IgM and IgG classes of anti-R. africae antibodies. After 1 year, only two patients still had measurable circulating antibodies. Cross-reactions with R. conorii were noted. Three patients were cured after a short course of doxycycline; one required 15 days of treatment.

CONCLUSIONS: ATBF is a benign disease increasingly being diagnosed in travelers. After ruling out malaria, ATBF diagnosis relies upon a detailed travel history and the classical findings of influenza-like symptoms, fever, one or more necrotic eschars, and rash. Serologic tests usually help to confirm the diagnosis. Neuropsychiatric symptoms specifically associated with ATBF are reported here for the first time.