Mediterranean spotted fever: a preliminary tick field study.

We studied the prevalence of rickettsialike organisms infection in different tick species (3154 adults) collected in several areas of the Ebro valley (Spain). The Gimenez stain showed a prevalence of rickettsia-like organisms in 38.6% of the studied ticks. Using the immunofluorescence assay, only two species, Rhipicephalus sanguineus (16.4%) and R. pusillus (19.9%) have shown organisms compatible with spotted fever group rickettsiae.