Comparison of Immunofluorescence, Western Blotting, and Cross-Adsorption Assays for Diagnosis of African Tick Bite Fever

In testing paired serum samples from 40 consecutive cases of African tick bite fever, we detected diagnostic antibodies against spotted fever group rickettsiae in 45% of the patients by immunofluorescence assay (IFA) and in 100% of the patients by Western blotting (WB) (P < 0.01). A specific diagnosis of Rickettsia africae infection could be established in 15% of the patients by IFA and in 73% of the patients by a combination of WB and cross-adsorption assays (P < 0.01). African tick bite fever (ATBF) is a flu-like illness frequently accompanied by inoculation eschars, headache, and neck myalgia (7). The disease is caused by Rickettsia africae, a recently identified spotted fever group (SFG) rickettsia, and is transmitted by cattle ticks in large parts of rural sub-Saharan Africa (9). ATBF typically occurs in clusters and has recently emerged