First detection of spotted fever group rickettsiae inIxodes ricinusandDermacentor reticulatusticks in the UK

Abstract

SUMMARYA preliminary study was conducted to determine the presence of spotted fever rickettsiae in two species of British tick (Ixodes ricinusandDermacentor reticulatus). The 16S rRNA gene ofRickettsiaspp. was detected in 39/401 (9·7%) of ticks tested, including 22/338 (6·5%)I. ricinusand 17/63 (27%)D. reticulatus. Some positiveI. ricinussamples showed 100% homology withRickettsia helvetica(10/22), and most positiveD. reticulatusshowed 100% homology withR. raoultii(13/17). Five otherRickettsiaspp. were detected exhibiting 96–99% homology. Ticks positive for rickettsiae were collected from various hosts and from vegetation from eight counties across Great Britain. The distribution ofR. helveticain various engorged and unfed stages ofI. ricinussuggests thatR. helveticais widespread.R. raoultiiwas found in questing adultD. reticulatusin Wales and England. This is the first evidence of potentially pathogenic spotted fever rickettsiae in British ticks.