Rickettsiae in Ixodid Ticks, Sicily

To the Editor: Members of the spotted fever group rickettsiae are intracellular bacteria usually associated with ixodid ticks, which are transferred to vertebrates by salivary secretions and within ticks transtadially and transovarially. Several tickborne rickettsiae cause human or animal diseases and, in the last 10 years, the increased use of molecular-based identification methods has resulted in new spotted fever group rickettsiae being characterized in ixodid ticks throughout Europe (1). Until recently, no rickettsiae, other than Rickettsia conorii, were reported in Italy. Since 2002, R. helvetica and Israeli spotted fever Rickettsia (R. conorii complex) have been detected in Ixodes ricinus and Rhipicephalus sanguineus, respectively (2–4). In Italy, Mediterranean spotted fever is endemic. This disease appears to occur more commonly in some central and southern regions (5); in 2002, more than half (498 of 890) of the cases of Mediterranean spotted fever identified in Italy and reported to the Ministry of Health came from Sicily.