MEMBERS of the order Chlamydiales are obligate intracellular bacteria identified within a wide host range. The order currently includes nine families: Chlamydiaceae, Clavichlamydiaceae, Criblamidiaceae, Piscichlamydiaceae, Parachlamydiaceae, Rhabdochlamydiaceae, Simkaniaceae, Waddliaceae and Parilichlamydiaceae (Everett and others 1999, Corsaro and Greub 2006, Greub 2010, Stride and others 2013). Previous studies have shown that vector transmission of Chlamydiales bacteria is possible (Caldwell and Belden 1973, McKercher and others 1980). Two recent studies on very large numbers of ticks emphasised the high prevalence and diversity of Chlamydiales DNA, suggesting ticks are vectors for Chlamydiales propagation to both human beings and animals (Croxatto and others 2014, Pilloux and others 2015). In Italy, Chisu and others (2015) found an 18 per cent prevalence of Chlamydiales DNA in arthropods from soil and animals in Sardinia. The study aimed to assess the prevalence and sequence diversity of Chlamydiales 16S rDNA in questing ticks collected in three parks of Northern Italy. From April to October 2010, 2284 ticks were collected by flagging low vegetation at four different sites distributed along the hilly part of the Emilia-Romagna Apennines (Northern Italy). Sites A (44°26′32″N, 11°26′30″E, 66 m asl) and B (44°24′57″N, 11°27′16″E, 240 m asl) were selected in the ‘Gessi Bolognesi and Calanchi dell'Abbadessa’ Regional Park. Site …