Demonstration of spotted fever group rickettsiae in the tache noire of a healthy person in Sicily.

A human case of rickettsial infection occurred in Sicily following tick bite. The patient did not have fever, the typical nodular rash, or other symptoms of illness other than development of a tache noire containing spotted fever group rickettsiae, which were demonstrated by immunofluorescence. A high titer of antibodies of the IgG class suggests that the patient may have had previous exposure to Rickettsia conorii or a related spotted fever group rickettsia. An anamnestic response may be hypothesized to have conferred partial immunity, with resulting containment of rickettsiae at the site of inoculation.