[Tick bites and paraspecific serologic reactions to Rickettsia conori].

During 1979 and 1980, 757 sera were tested for the presence of anti-R. conori antibodies by immunofluorescence; 99 sera were positive. The origin of 28 seropositive cases was outside of continental France, 45 cases come from Southern regions of France, but 26 cases from the North of France. Cases of the first two groups showed mostly symptoms of spotted fever and the titers of the sera were increasing or single high. Cases from North of France presented only cutaneous lesions resembling erythema migrant and serotiters were always low and invariable. Today such seroreactions must be considered as paraspecific but a working hypothesis is discussed.